Tani et al. International Journal of Behavioral Nutrition and Physical Activity(2020) 17:82
https://doi.org/10.1186/s12966-020-00986-9

RESEARCH

Open AccessCooking skills related to potential benefits
for dietary behaviors and weight statusamong older Japanese men and women: across-sectional study from the JAGES
Yukako Tani1* , Takeo Fujiwara1 and Katsunori Kondo2,3

Abstract
Background: Poor cooking skills have been linked to unhealthy diets. However, limited research has examinedassociations of cooking skills with older adults’ health outcomes. We examined whether cooking skills wereassociated with dietary behaviors and body weight among older people in Japan.
Methods: We used cross-sectional data from the 2016 Japan Gerontological Evaluation Study, a self-report,
population-based questionnaire study of men (n = 9143) and women (n = 10,595) aged ≥65 years. The cooking skills
scale, which comprises seven items with good reliability, was modified for use in Japan. We calculated adjusted
relative risk ratios of unhealthy dietary behaviors (low frequency of home cooking, vegetable/fruit intake; highfrequency of eating outside the home) using logistic or Poisson regression, and relative risk ratios of obesity andunderweight using multinomial logistic regression.
Results: Women had higher levels of cooking skills, compared with men. Women with a moderate to low level ofcooking skills were 3.35 (95% confidence interval [CI]: 2.87–3.92) times more likely to have a lower frequency ofhome cooking and 1.61 (95% CI: 1.36–1.91) times more likely to have a lower frequency of vegetable/fruit intake,compared with women with a high level of cooking skills. Men with a low level of cooking skills were 2.56 (95% CI:
2.36–2.77) times more likely to have a lower frequency of home cooking and 1.43 (95% CI: 1.06–1.92) times more
likely to be underweight, compared with men with a high level of cooking skills. Among men in charge of meals,
those with a low level of cooking skills were 7.85 (95% CI: 6.04–10.21) times more likely to have a lower frequencyof home cooking, 2.28 (95% CI: 1.36–3.82) times more likely to have a higher frequency of eating outside the home,and 2.79 (95% CI: 1.45–5.36) times more likely to be underweight, compared with men with a high level of cooking
skills. Cooking skills were unassociated with obesity.
Conclusions: A low level of cooking skills was associated with unhealthy dietary behaviors and underweight,
especially among men in charge of meals. Research on improving cooking skills among older adults is needed.
Keywords: Cooking skill, Home cooking, Eating out, Vegetable and fruit intake, Obesity, Underweight* Correspondence: tani.hlth@tmd.ac.jp
1
Department of Global Health Promotion, Tokyo Medical and Dental
University (TMDU), 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8519, Japan
Full list of author information is available at the end of the article© The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License,
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Tani et al. International Journal of Behavioral Nutrition and Physical Activity

Background
There are increasing calls to return to home cooking toprevent poor diets and chronic diet-related diseases [1].
A systematic review has reported the dietary benefits ofeating home-cooked meals, including greater consumption of fruits and vegetables, enhanced nutrient intake,and higher diet quality [2]. A recent cross-sectional
study showed that eating home-cooked dinners was associated with greater dietary guideline compliance, without significantly increasing food expenditures [3].
Although studies related to the effects of home cooking
on health outcomes are limited, a recent large
population-based study in the United Kingdom showedthat more frequent consumption of home-cooked meals
was associated with a greater likelihood of having normal weight and body fat status [4]. Furthermore, a cohort study targeting older people in Taiwan
demonstrated that older adults who cooked more than
five times per week had approximately 40% lower risk ofdeath, compared with those who did not cook [5]. The
study also showed a dose–response relationship, meaning that the risk of death decreased as the frequency ofhome cooking increased. Despite the benefits of homecooking, the consumption of home-cooked meals has
declined and the consumption of out-of-home foods,
such as fast food and convenience food, has increased inrecent decades in developed countries [6, 7].
Cooking skills are one important modifiable factor thatcan encourage people to cook [2]. In addition to increasing the frequency of home cooking, strengthening people’s cooking skills can improve their diet quality. For
example, cross-sectional studies have shown an association between high levels of cooking skills and lower
consumption of ready meals, convenience food, andultra-processed food among adults [8–10]. Intervention
studies have also shown improving cooking skills to increase cooking confidence and consumption of vegetables and fruits [11, 12]. Most existing studies havefocused on dietary benefits among adults, and limited
work has examined the associations between cooking
skills and health outcomes among older adults.
Population aging is increasing dramatically, and the percentage of the world’s population aged over 60 years is
projected to nearly double from 12% in 2015 to 22% in
2050 [13]. Overall, older adults do not meet the recommendations for a healthy diet [14]. Physiological, social,economic, and psychological factors affect older people’s
food choices. Physiological factors, such as age-related decline in taste and smell, can lead to decreased appetite andpoor dietary habits [15]. Social factors, including lower social engagement and living alone, are also associated withpoor diet quality [15, 16]. Economic factors such as low
income and retirement can negate older people’s ability tomeet their nutritional needs [17, 18]. Finally, psychological(2020) 17:82

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factors including wellbeing and depression are also associated with eating behaviors [16]. However, although cooking skills are a fundamental factor in preparing meals, theeffects of cooking skills on dietary behaviors do not seemto have been evaluated among older adults. A systematic
review demonstrated associations between culinary interventions and improved dietary factors, including attitudes,
self-efficacy, and healthy dietary intake among adults [19].
Focusing on cooking skills as a modifiable factor amongolder adults is an innovative approach.
The rationales described above indicate that having sufficient cooking skills may be important for healthy aging.
More older adults live alone, compared with other age
groups: In 43 developing countries, only 1.6% of people
were found to live alone overall, compared with 8.8% of
older adults [20]. In Japan, most older people live alone orwith their spouses [21]. Thus, older adults are faced withthe task of preparing own meals. Because of changes inliving arrangements or spouses becoming unable to cook,
the person responsible for cooking at home may change
in older age. For example, a widowed man may be incharge of cooking for the first time. Because it is mainly
women who are in charge of preparing meals, men havebeen found to be less confident in their cooking and tohave lower levels of cooking skills [9, 22]. Therefore, men,
especially widowed men or men whose spouses are unable
to cook, may be at risk of diet-related problems because of
their poor cooking skills. To our knowledge, no study has
examined the associations between cooking skills andhealth outcomes among older people who are in charge ofmeals.
One reason for the limited evidence relating to cooking skills may be the difficulty of assessing cooking skills.
Cooking skills have been defined as a set of mechanicalor physical skills used in meal preparation, such as chopping, mixing, and heating basic ingredients, as well as
conceptual skills related to understanding how food willreact when cooked [23]. In addition to the various aspects of cooking skills, the cooking skills required varydepending on culture: For example, cooking methods(e.g., grilling, steaming, stewing, and stir-frying) differ byculture. Several methods have been used to measurecooking skills, but there are few validated and reliablemeasures of cooking skills [23]. Hartmann et al. conducted a test-retest analysis and designed a reliablecooking skills scale comprising seven items related tothe ability to prepare different foods that is applicable tomost European cultures [9]. Because this scale rates theability to prepare general food groups (e.g., bread), it ismore versatile than scales that rate the ability to prepare
specific meals (e.g., spaghetti Bolognese). Therefore, forthe present study, we modified this scale for application
in a Japanese population. The first aim of our study wasto assess the reliability of this scale in a large-scaleTani et al. International Journal of Behavioral Nutrition and Physical Activity

Japanese population-based study. The second aim was to
examine the associations of cooking skills with the frequency of home cooking, the frequency of eating outside
the home, the frequency of vegetable/fruit consumption,and body weight status.

Methods
Study design and participants

The Japan Gerontological Evaluation Study (JAGES), alarge nation-wide research project on aging, was established in 2010 to evaluate the social determinants ofhealthy aging among older people in Japan [24, 25]. We
used data from the 2016 JAGES, which covered 39 municipalities across Japan and was administered tocommunity-dwelling older adults who were physicallyand cognitively independent (i.e., without functional disabilities, defined as not being certified as eligible to receive long-term public care insurance system services[26]). From October 2016 to January 2017, self-reportquestionnaires were mailed to 279,661 older adults aged
≥65 years. The survey was conducted using random sampling in 22 large municipalities and was administered toall eligible residents in 17 small municipalities. A total of
196,438 participants returned the questionnaire (response rate: 70.2%). In some municipalities, recipients
receiving long-term public care insurance benefits were
included in the survey by request of the local government, so the target sample was 180,021 older adults,
after excluding those who received these benefits. Oneeighth of the sample (N = 22,219) were randomly selected to receive a survey module on cooking skills. The
present analysis was carried out using data for 19,738
participants (9143 men and 10,595 women), after thefollowing exclusions: participants with missing information on gender (N = 2); participants who did notcomplete the questions related to height and weight(N = 660) or dietary behaviors (frequency of home cooking, eating outside the home, and vegetable/fruit intake)(N = 1475); participants with missing data on the cooking skills scale (N = 145); and participants who were included in this study accidentally who reported
limitations in activities of daily living (N = 199) to ensurethat the sample was actually physically and cognitively
independent. Limitations in activities of daily living wereassessed with the Independence in Activities of Daily
Living index [27] using the following questionnaire item:“Do you need any nursing care or assistance from someone in your daily life?” We excluded participants who
answered “I need and receive nursing care or assistance.”
Participants were informed that participation in the
study was voluntary and that completing and returning
the questionnaire indicated their consent to participate
in the study. The JAGES protocol was approved by the
Ethics Committee in Research of Human Subjects at the(2020) 17:82

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National Center for Geriatrics and Gerontology (No.
992) and Chiba University Faculty of Medicine (No.
2493).
Body weight status and dietary behaviors

Participants reported their height in centimeters andweight in kilograms. Body mass index (BMI) was calculated as weight divided by the square of height (kg/m2).
We defined underweight as having a BMI < 18.5 kg/m2
and obesity as having a BMI ≥ 27.5 kg/m2, following thesuggested cutoff points for Asians [28]. The evaluateddietary behaviors were the frequency of home cooking,eating outside the home, and vegetable/fruit intake. The
frequency of home cooking was assessed using the question “How often do you cook by yourself? Do not include ready-to-eat food” (responses: more than five times
a week, three to five times a week, one to two times aweek, less than once a week, and never). Respondents
who cooked less than two times a week were categorized
as having a low cooking frequency for women because
more than three times a week has been shown to predictsurvival among older women [5]. For men, respondents
who never cooked were categorized as having a low
cooking frequency because more than half of the men
indicated that they never cooked (Table 1). The frequency of eating outside the home was assessed using
the question “How often do you eat outside the home?”
The responses for this item were the same as those forthe frequency of home cooking. Respondents who ate
outside the home more than three times a week werecategorized as having a high frequency of eating outside
the home because eating outside the home more than
three times a week has been shown to be related tohigher BMI and lower serum concentrations of nutrients[29]. The frequency of vegetable and fruit intake wasassessed using the question “How often did you eat vegetables and fruits over the past month?” (responses: not at
all, less than once a week, once a week, two to three times
a week, four to six times a week, once a day, and at least
twice a day) [30, 31]. Respondents who ate vegetables andfruits less than once a day were categorized as having a
low frequency of vegetable and fruit intake. This cutoff
point was defined by prevalence to be under 25% of subjects included (Table 1) because being in the lowest quartile for vegetable and fruit intake has been shown to be
associated with poor health outcomes [32–34].
Cooking skills

As mentioned above, based on the cooking skills scale
for European cultural regions [9], we adapted Hartmann’s a cooking skills scale for use in Japanese populations. In Japan, a typical meal—known as ichi-ju sansai—consists of a staple food (such as rice), a soup (usually miso), and three dishes (one main dish and two sideTani et al. International Journal of Behavioral Nutrition and Physical Activity(2020) 17:82

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Table 1 Characteristics of older Japanese men and women by level of cooking skills (n = 19,378)
Males (n = 9143)
Totaln

Females (n = 10,595)
Cooking skill

%

Total

High

Middle

Low

%

%

%
0

9968

p-valuen

Cooking skill%

High

Middle/Low

%

%

94.1

100.0

0

p-value

Cooking skill
High

4751

52.0

100

0

Middle

3269

35.8

0

100

0

498

4.7

0

79.4

Low

1123

12.3

0

0

100

129

1.2

0

20.6

65–69

2855

31.2

32.7

29.8

29.2

3269

30.9

31.7

18.0

70–74

2510

27.5

26.9

29.1

25.1

2893

27.3

27.8

19.9

75–79

2059

22.5

22.9

22.3

21.4

2393

22.6

22.8

19.8

≥ 80

1719

18.8

17.5

18.8

24.3

2040

19.3

17.8

42.3

Low (≤9)

2626

28.7

28.2

28.1

32.7

3614

34.1

33.3

46.4

Middle (10–12)

3461

37.9

36.8

39.4

37.9

4638

43.8

44.2

37.0

High (≥13)

2981

32.6

34.1

31.8

28.8

2198

20.7

21.1

14.7

Other/Missing

75

0.8

0.9

0.8

0.6

145

1.4

1.3

1.9

Low (< 2.00)

3485

38.1

37.5

38.6

39.4

4110

38.8

38.5

43.1

Middle (2.00–3.99)

3279

35.9

35.9

36.6

33.3

3049

28.8

29.3

21.1

High (≥4.00)

924

10.1

10.6

9.3

10.6

885

8.4

8.5

5.9

Missing

1455

15.9

16

15.4

16.7

2551

24.1

23.7

30.0

Married

7788

85.2

81.6

88.0

92.0

6497

61.3

62.4

44.7

Widowed

631

6.9

8.5

5.4

4.3

3097

29.2

28.3

43.9

Divorced

321

3.5

4.7

2.6

1.2

513

4.8

4.8

5.1

Single

257

2.8

3.4

2.6

1.0

307

2.9

2.8

4.1

Other/Missing

146

1.6

1.8

1.3

1.5

181

1.7

1.7

2.2

Age (years)< 0.001< 0.001

Education (years)
0.002< 0.001

Annual income (million yen)0.215

< 0.001

Marital status< 0.001< 0.001

Under medical treatment
Cancer (Yes)

450

4.9

5.1

4.5

5.7

0.53

355

3.4

3.3

4.3

0.35

Heart disease (Yes)

1219

13.3

13

13.6

14.2

0.84

713

6.7

6.5

9.7

0.008

Stroke (Yes)

385

4.2

3.5

4.5

6.5

< 0.001

184

1.7

1.6

4.1

< 0.001

Diabetes mellitus (Yes)

1484

16.2

16.6

15.3

17.4

0.47

1010

9.5

9.5

10.4

0.69

Hypertension (Yes)

3913

42.8

42.1

43.5

43.8

0.66

4391

41.4

41.0

48.2

0.002

Hyperlipidemia (Yes)

933

10.2

10.3

10.4

9.4

0.92

1658

15.6

15.8

13.2

0.19

Cook by yourself

1283

14.0

22.2

6.1

2.2

< 0.001

8714

82.2

84.0

54.9

< 0.001

Family member cook

6785

74.2

65.1

82.5

88.5

977

9.2

7.9

30.3

Buy cooked meals

307

3.4

2.8

4.3

2.8

132

1.2

1.1

4.1

Main way of preparing meals

Use home-delivery services

81

0.9

0.9

0.7

1.4

46

0.4

0.4

1.0

Other/Missing

687

7.5

8.9

6.3

5.1

726

6.9

6.7

9.7

8762

82.7

84.6

51.8

902

8.5

8.3

11.8

Frequency of home cooking (n/week)≥ 5 /week

1310

14.3

23.3

5.8

1.2

3–4 /week

757

8.3

12.5

4.6

1.1

< 0.001< 0.001(2020) 17:82

Tani et al. International Journal of Behavioral Nutrition and Physical Activity

Page 5 of 12

Table 1 Characteristics of older Japanese men and women by level of cooking skills (n = 19,378) (Continued)
Males (n = 9143)
Totaln

Females (n = 10,595)
Cooking skill

%

Total

High

Middle

Low

%

%

%

p-valuen

Cooking skill%

High

Middle/Low%%

1–2 /week

1002

11

15.3

7.7

2.0

366

3.5

3.2

8.1

< 1 /week

1157

12.7

15.2

12.4

2.8

199

1.9

1.5

7.2

Never

4917

53.8

33.7

69.6

92.9

366

3.5

2.3

21.1

103

1.0

0.9

1.4

268

2.5

2.6

2.1

p-valueFrequency of eating outside the home (n/week)≥ 5 /week

242

2.6

2.6

2.3

3.7

3–4 /week

462

5.1

5.0

5.4

4.2

< 0.001

1–2 /week

1450

15.9

16.9

15.6

12.3

1268

12.0

12.1

10.4

< 1 /week

3773

41.3

41.3

41.9

39.2

4297

40.6

41.0

34.1

Never

3216

35.2

34.2

34.7

40.7

4659

44.0

43.5

52.0

0.001

Frequency of vegetable/fruit intake (n/day)≥ 1 /day

6625

72.5

73.3

70.6

74.4

< 1 /day (low frequency)

2518

27.5

26.7

29.4

25.6

428

4.7

4.1

5.1

5.8

0.008

9052

85.4

86.0

75.9

1543

14.6

14.0

24.1

988

9.3

9.2

11.8

< 0.001

Body weight status (BMI, kg/m2)
Underweight (< 18.5)

0.04

Normal (18.5–27.4)

8044

88.0

88.1

88.0

87.4

8833

83.4

83.5

81.5

Obesity (≥ 27.5)

671

7.3

7.8

6.9

6.9

774

7.3

7.3

6.7

0.08

BMI body mass index

dishes) [35]. The basic Japanese cooking methods—
Gohou (five methods)—are raw food, boiling, grilling,steaming, and frying [36]. We adopted stewing insteadof steaming to reflect contemporary cooking practices[37]. Therefore, we included these elements and designed the following seven items for the Japanese versionof the cooking skills scale: “How do you assess youroverall cooking skills?”; “Can you peel fruits and vegetables?”; “Can you boil eggs and vegetables?”; “Can you
grill fish?”; “Can you make stir-fried meat and vegetables?”; “Can you make miso soup?”; and “Can you makestewed dishes?” Participants were asked to evaluate theirown cooking skills on a six-point scale (ranging from 1
for unable to 6 for very well). Cronbach’s α for theseseven items was 0.96. Cronbach’s α was calculated using
an unstandardized approach for respondents answering
five or more of the seven items. The mean of the seven
items was calculated for each respondent to reflect theiroverall cooking skills; the midpoint was 3.5, and a highscore meant that the respondent had high confidence intheir cooking skills (Table 2). The mean cooking skills
score was divided into three categories—high (> 4.0),
middle (2.1–4.0), and low (≤ 2.0)—to examine the associations of cooking skills with body weight status anddietary behaviors. For women, because the distributionof the cooking skills score was skewed to the left (leaning towards higher scores), the middle and low groups
were merged into one category. Therefore, women wereclassified into two cooking skills categories: high (> 4.0)
and middle/low (≤ 4.0).
Person in charge of meal selection

Participants were asked “In what way are your daily
meals mainly prepared?” The responses to this item wereas follows: cook by myself, a family member cooks, buy
packaged lunches or cooked meals, use catering or homedelivery services, and other. Participants except for those
who reported that a family member did the cooking
were defined as being in charge of preparing or selecting
meals.
Covariates

Covariates were assessed using the self-report questionnaire. Age was divided into four categories (65–69, 70–
74, 75–79, and ≥ 80 years). The duration of education
was divided into three categories (≤ 9 years, 10–12 years,and ≥ 13 years). Annual household income was adjusted
for household size, dividing the household income by
the square root of the number of people in the household. This variable was then divided into three categories(< 2.00, 2.00–3.99, and ≥ 4.00 million yen). Marital status
was divided into five categories (married, widowed, divorced, single, and other). To assess comorbidity, theparticipants were asked whether they were currently
under medical treatment for any of the following conditions (multiple responses were allowed): cancer, heartTani et al. International Journal of Behavioral Nutrition and Physical Activity

disease, stroke, hypertension, diabetes mellitus, andhyperlipidemia. Covariates with missing data were categorized as “missing.”
Statistical analysis

The analyses were stratified by gender because a previous study reported different associations between cooking skills and dietary behaviors by gender and distinct
patterns of potential confounders for men and women[9]. First, participants were stratified by cooking skill
level, and differences between groups were tested using
Pearson’s chi-squared tests. Second, multiple comparisons
for the cooking skills scale were analyzed using the mixed
linear model procedure to examine which cooking skills
participants rated as difficult. The model adjusted for age,education, annual normalized household income, marital
status, and medical treatment (cancer, heart disease,stroke, diabetes mellitus, hypertension, and hyperlipidemia), and peeling was used as the reference category. Participant identification code was included as a random
effect. Third, we calculated adjusted odds ratios with 95%
confidence intervals (CIs) of high frequency of eating outside the home using logistic regression. For low frequencyof home cooking and vegetable/fruit intake, we calculated
adjusted prevalence ratios (APRs) with 95% CIs using
Poisson regression because participants with low frequencies of home cooking and vegetable/fruit intake were notuncommon, so the odds ratios derived from logistic regression would have been unable to approximate theprevalence ratio [38, 39]. For the association with weightstatus, we calculated adjusted relative risk ratios (ARRRs)
with 95% CIs of underweight and obesity using multinomial logistic regression, with the body weight categoryof BMI of 18.5–27.4 kg/m2 as the reference category. The
models were adjusted for the following potential confounding factors: age, education, annual normalized
household income, and medical treatment for cancer,
heart disease, stroke, hypertension, diabetes mellitus, andhyperlipidemia. Participants with missing data on the covariates were included in the analysis. All analyses wereconducted using Stata, Version 14 (Stata Statistical Software: Release 14. College Station, TX: StataCorp LP).

Results
The participants’ characteristics are summarized inTable 1. A total of 46% of the participants were men,about 20% were aged over 80 years, 30% had under 9
years of education, and 40% had annual incomes below
two million yen. Of the male respondents, about 10%
were widowed or divorced. When cognitive function wasassessed with three items from the Kihon Checklist–
Cognitive Function scale, for which predictive validity
for dementia incidence has previously been confirmed[40], only 0.9% of participants had three cognitive(2020) 17:82

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complaints. The majority of women (94.1%) were classified as having a high level of cooking skills (Table 1). For
men, the level of cooking skills was classified as high for
52.0%, middle for 35.8%, and low for 12.3%. For women,
8.9% cooked less than two times a week, 3.5% ate out
more than three times a week, 14.6% ate vegetables/
fruits less than once a day, 9.3% were underweight, and7.3% were obese. For men, 53.8% never cooked, 7.7% ate
out more than three times a week, 27.5% ate vegetables/
fruits less than once a day, 4.7% were underweight, and7.3% were obese. Women with middle/low-level cooking
skills tended to be older, have a low level of education,
have low income, not be married, and list a family member as the main meal preparer (Table 1). For men, in
addition to being older, having a low level of education,and having a family member as the main meal preparer,
men who were married tended to have a low level ofcooking skills (Table 1).
The mean cooking skills score was higher for women(5.6 points) than for men (4.1 points) (t (19736) = − 99.6,
p < 0.001) (Table 2). For psychometric testing, one factor
with an eigenvalue over 1 was found, and this accounted
for 80.5% of the variance. All factor loadings were 0.8 orhigher. Men rated stewing and stir-frying as more difficult than peeling. Although women had statistically significant differences between the assessed cooking skills,
in terms of substantive significance, they rated all themethods assessed on the cooking skills scale as being ofsimilar difficulty (Table 2).
There were gender differences in the associations of
cooking skills with unhealthy dietary behaviors and bodyweight status (Table 3). Women with a middle/low levelof cooking skills were 3.35 times (95% CI: 2.87–3.92)
more likely to have a lower frequency of home cooking
and 1.61 (95% CI: 1.36–1.91) times more likely to have alower frequency of vegetable/fruit intake, compared withwomen with a high level of cooking skills. As for weightstatus, women with a middle/low level of cooking skills
were 1.29 (95% CI: 0.99–1.67) times more likely to beunderweight, compared with women with a high level ofcooking skills. For men, compared with those with ahigh level of cooking skills, men with a middle or low
level of skill were 1.98 (95% CI: 1.86–2.11) times more
likely and 2.56 (95% CI: 2.36–2.77) times more likely, respectively, to have a lower frequency of home cooking.
Regarding eating outside the home, compared with men
with a high level of cooking skills, men with a low levelof cooking skills were 1.30 (95% CI: 1.01–1.67) times
more likely to have a higher frequency of eating outside
the home. There was a significant association with a low
frequency of vegetable/fruit intake only among men witha middle level of cooking skills (APR: 1.15, 95% CI:
1.06–1.26). As for weight status, compared with men
with a high level of cooking skills, men with middle or(2020) 17:82

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Table 2 Cooking skills among older Japanese men (n = 9143) and women (n = 10,595)
Items

Males

Overall cooking skills

Females

mean

SD

Coef

p-value

mean

SD

Coef

p-value

3.15

1.53

−1.60

< 0.001

4.99

1.12

−0.77

< 0.001

Able to peel fruits and vegetables

4.75

1.44

reference

5.76

0.74

reference

Able to boil eggs and vegetables

4.58

1.56

−0.17

< 0.001

5.78

0.73

0.02

0.007

Able to grill fish

4.24

1.72

−0.50

< 0.001

5.70

0.86

−0.06

< 0.001

Able to make stir-fried meat and vegetables

4.04

1.76

−0.70

< 0.001

5.72

0.82

−0.04

< 0.001

Able to make miso soup

4.16

1.77

−0.59

< 0.001

5.74

0.80

−0.02

0.001

Able to make stewed dishes

3.43

1.81

−1.32

< 0.001

5.72

0.82

−0.05

< 0.001

Cooking skill scale

4.05

1.42

5.63

0.74

Multiple comparisons between cooking skills scale were analyzed using the mixed linear models procedure adjusted for age, education, annual normalized
household income, marital status and medical treatment (cancer, heart disease, stroke, diabetes mellitus, hypertension and hyperlipidemia). Participant
identification code was included as a random effectlow skill levels were 1.29 (95% CI: 1.04–1.60) times more
likely and 1.43 (95% CI: 1.06–1.92) times more likely, respectively, to be underweight. There was no significant
association between cooking skills and obesity for eithermen (p = 0.33) or women (p = 0.40). Using the cutoff
point of BMI ≥ 23.0 kg/m2 as overweight, we found thata low level of cooking skills was not associated with anincreased risk of overweight (Supplementary Table 1).
Next, we focused on men in charge of meals. Over
90% of women (n = 9618) but only 26% of men (n =2358) were in charge of daily meals. In contrast to men
not in charge of preparing meals, most men in charge ofmeals rated their cooking skills as high (Supplementary
Table 2). Men in charge of meals tended to have lowlevels of education and low income and to be unmarried(e.g., widowed or divorced) (Supplementary Table 2).
When the associations with unhealthy dietary behaviors
and weight status were examined for men in charge ofmeals, the effect size increased (Table 4). Compared withmen with a high level of cooking skills, men with middle- or low-level cooking skills were 4.22 (95% CI: 3.42–5.21) times more likely and 7.85 (95% CI: 6.04–10.21)
times more likely, respectively, to have a lower frequencyof home cooking (Table 4). Regarding eating outside thehome, compared with men with a high level of cooking
skills, men with a low level of cooking skills were 2.28
(95% CI: 1.36–3.82) times more likely to have a higher
frequency of eating outside the home. In relation to low
frequency of vegetable/fruit intake, the APR for men
with a middle level of cooking skills was 1.32 (95% CI:
1.15–1.53). Furthermore, compared with men with ahigh level of cooking skills, men with middle or low skill
levels were 1.59 (95% CI: 1.04–2.45) times more likely
and 2.79 (95% CI: 1.45–5.36) times more likely, respectively, to be underweight.

Table 3 Adjusted prevalence/odds ratios/relative risk ratios of unhealthy eating behaviors, underweight, and obesity by level ofcooking skills among older Japanese men (n = 9203) and women (n = 10,847)
Low frequency ofhome cookingaHigh frequency of eating
outside the homeb

Low frequency of vegetableand fruit intakec

Underweightd

ObesityeAPR (95%CI)

AOR (95%CI)

APR (95%CI)

ARRR (95%CI)

ARRR (95%CI)

Men
Cooking skill

High

ref

ref

ref

Middle1.98 (1.86–2.11)

1.15 (0.97–1.36)

1.15 (1.06–1.26)

1.29 (1.04–1.60)

ref0.89 (0.75–1.06)

Low

2.56 (2.36–2.77)

1.30 (1.01–1.67)

1.04 (0.91–1.18)

1.43 (1.06–1.92)

0.88 (0.68–1.14)

1.29 (0.99–1.67)

0.87 (0.62–1.21)

Women
Cooking skill

High

ref

ref

ref

Middle-Low

3.35 (2.87–3.92)

0.97 (0.62–1.52)

1.61 (1.36–1.91)

refAOR adjusted odds ratio, APR adjusted prevalence ratio, ARRR adjusted relative risk ratio, BMI body mass index, CI confidence intervala
Low frequency of home cooking: frequency of home cooking ≤2 times/week for women and 0 times/week for menbHigh frequency of eating outside the home: frequency of eating outside the home ≥3 times/weekc
Low frequency of vegetable and fruit intake: frequency of vegetable and fruit intake < 1/daydUnderweight: BMI < 18.5 kg/m2
eObesity: BMI ≥ 27.5 kg/m2
The models were adjusted for age, education, annual normalized household income, marital status, and medical treatment (cancer, heart disease, stroke, diabetes
mellitus, hypertension, and hyperlipidemia)

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Table 4 Adjusted prevalence ratios/relative risk ratios of low frequency of vegetable/fruit intake and home cooking, underweight,
and obesity by cooking skills level among older Japanese men in charge of meals (n = 2370)
Low frequency ofhome cookingaHigh frequency ofeating outb

Low frequency of vegetableand fruit intakec

Underweightd

ObesityeAPR (95%CI)

AOR (95%CI)

APR (95%CI)

ARRR (95%CI)

ARRR (95%CI)

Men in charge of cooking
Cooking skill

High

ref

ref

ref

ref

Middle4.22 (3.42–5.21)

1.63 (1.22–2.17)

1.32 (1.15–1.53)

1.59 (1.04–2.45)

0.91 (0.63–1.32)

Low

7.85 (6.04–10.21)

2.28 (1.36–3.82)

1.12 (0.84–1.50)

2.79 (1.45–5.36)

0.59 (0.25–1.39)

AOR adjusted odds ratio, APR adjusted prevalence ratio, ARRR adjusted relative risk ratio, BMI body mass index, CI confidence intervala
Low frequency of home cooking: frequency of home cooking 0 times/weekbHigh frequency of eating outside the home: frequency of eating outside the home ≥3 times/weekc
Low frequency of vegetable and fruit intake: frequency of vegetable and fruit intake < 1/daydUnderweight: BMI < 18.5 kg/m2
eObesity: BMI ≥ 27.5 kg/m2
The models were adjusted for age, education, annual normalized household income, marital status, and medical treatment (cancer, heart disease, stroke, diabetes
mellitus, hypertension, and hyperlipidemia)

Discussion
To the best of our knowledge, this is the first study to
examine the associations of cooking skills with unhealthy dietary behaviors and weight status by genderand meal preparer status among older adults. Using an
adapted version of an existing cooking scale for use inJapanese populations, we confirmed that women had
higher levels of cooking skills than did men and that theassociations of cooking skills with dietary behaviors andweight status differed by gender. For both men andwomen, a low or middle/low level of cooking skills was
associated with a low frequency of home cooking. Having low- or middle/low-level cooking skills was found tobe significantly associated with high frequency of eating
outside the home and with being underweight for men
but not for women. The association between low or
middle/low level of cooking skills and low frequency ofvegetable/fruit intake was found for both men andwomen, but among men there was no dose–response relationship. The associations of low level of cooking skills
with unhealthy dietary behaviors and underweight status
were especially pronounced among men in charge ofmeals. Cooking skills were unassociated with obesity
among both women and men.
In this study, a cooking skills scale for use in Japanese
populations was designed with consideration of basic Japanese cooking methods and typical meals. Although we did
not confirm the validity of this newly designed cooking skills
scale by objective assessment, we were able to obtain plausible results, with the same trends observed with the original
cooking skills scale for European populations [9]. Our cooking skills scale had appropriate internal consistency (Cronbach’s α = 0.96) and showed higher values for women andthose with higher education levels, which is consistent withprevious findings [9, 41]. This result also supports previous
findings of a gender difference in confidence in cooking
skills indicating that women are more confident in theircooking skills than are men [9, 22, 42]. The differences incooking skills by gender and educational attainment among
Japanese older adults may be explained by opportunities tolearn cooking skills in school. In Japan, cooking education inschools was conducted exclusively for women until 1989;
therefore, the men in this study (born before 1958) had less
opportunity to learn cooking in school [43]. Another factor
is that older age is associated with a stronger belief in thegender role ideology holding that men should work outside
the home and women should do housework inside thehome. In earlier years, there was even a cultural idea thatmen should not so much as enter the kitchen. This idea isreflected in the saying “Danshi-chubo-ni-hairazu” (“A man
would be ashamed to be found in the kitchen”) [44]. However, men’s mean (SD) cooking skills score of 4.1 (1.42) was
higher than the midpoint of 3.5, indicating that older Japanese men have above-average confidence in their cooking
skills. In line with previous studies on adults showing thatlevels of cooking skills tend to be high in multiple-personhouseholds [8, 9], we found that women’s cooking skills
were higher when they were married than when they were
not. However, in contrast, men’s cooking skills were higher
when they were not married (e.g., widowed or divorced).
This result is intuitive because unmarried men do not havea spouse who is responsible for the cooking. We speculatethat unmarried women have a moderate level of cooking
skills because they were taught to cook in home economics
classes and by their mothers, but their cooking skills may
not have continued to improve because there was no needto cook for another person. Interventions earlier in the life
course, such as at retirement, may be effective because men
have a high risk of unhealthy eating behavior caused by theirpoor cooking skills if they are later widowed or divorced.
We included five basic cooking methods in the cooking skills scale, finding that men rated stewing and stirfrying as more difficult, compared with peeling and boiling. A previous study that examined eight cooking

Tani et al. International Journal of Behavioral Nutrition and Physical Activity

methods in the United Kingdom showed that men weremore confident about boiling, compared with stewing or
stir-frying [42]. This result is plausible because stewing
and stir-frying require adjusting the level of heat andadding seasoning to prepare the dish properly. In interventions targeting men, it might be most beneficial tofocus on simple cooking methods using stewing andstir-frying.
As expected, having a low or middle/low level of cooking skills was significantly associated with having a low
frequency of home cooking for both men and women.
People with high levels of cooking skills may enjoy cooking and feel self-confident regarding their cooking, leading to a high frequency of home cooking [9, 42].
However, a significant association between a low level ofcooking skills and high frequency of eating outside thehome was found only among men. This result may reflect the gender difference in the prevalence of eating
outside the home. The percentage of respondents who
ate out at least once a week was 15.5% for women and23.6% for men (Table 2). A previous nationally representative survey in Japan reported that this gender difference exists across all age groups in the country,
suggesting that men tend to prefer eating outside thehome [45]. The same national survey also reported thatthe percentage of people who consume packaged
lunches or cooked meals is the same for both men andwomen [45]. Therefore, women may consume thesemeals rather than eating outside the home, even if they
have a low level of cooking skills. Another possible reason for the gender difference in eating outside the home
is that there is a fundamental difference in cooking ability between men and women. In other words, the men
who were categorized as having a low level of cooking
skills cannot prepare any kind of meal, but the women
who were categorized as having a middle/low level ofcooking skills may be able to make basic meals. In ourstudy, 79% of the women categorized as having a middle/low level of cooking skills were originally in the
middle-level cooking skills category (Table 1). Therefore,
women may not have to rely on eating outside the homeeven if they have a middle/low level of cooking skills.
Unlike home cooking and eating outside the home, nodose–response relationship between cooking skills andlow vegetable/fruit intake was observed among men. In aprevious study using the original cooking skills scale in
Switzerland, favorable associations between cooking skills
and various food groups including vegetables and fruits
were evident for women, but these associations were weakor nonexistent for men [9]. This gender difference may be
explained by nutritional knowledge [22, 46]: Men may nothave sufficient nutritional knowledge regarding healthy
food choice, even if they have a high level of cooking skills.
Additionally, men may be more likely to choose foods(2020) 17:82

Page 9 of 12

because of their sensory appeal rather than for health reasons [47]. Future work should investigate food skills, including meal planning, food safety, and nutrition
knowledge [23].
A low level of cooking skills was associated with
underweight but not with obesity. Although a low levelof cooking skills was associated with a high frequency ofeating outside the home among men, which is generally
associated with obesity, the majority of older Japanesepeople participating in this study did not rely on eating
outside the home. The percentage of people who ate out
more than three times a week was only 5% for the study
participants, compared with 35% for older Americans
aged 60 years or older [29]. In our sample, more than
90% of the participants reported that their daily meals
were mainly cooked by themselves or a family member(Table 1). Therefore, for older Japanese people, a low
cooking frequency because of a low level of cooking
skills may mean that they skip meals or eat simple meals
or meals with poor nutritional value instead of eating
outside the home. This would be more likely to lead tounderweight than to obesity. A study examining theamount of rice served at local and chain restaurants inJapan found that most restaurants set the rice potion at
an appropriate quantity for middle-aged and older
people (> 160 g and < 200 g) [48]. Therefore, those eating
outside the home in Japan may be unlikely to consume ahigh number of calories. When we additionally included
frequency of home cooking and vegetable/fruit intake as
potential mediators in our model, the ARRR of underweight decreased and became statistically non-significant
among men, although it remained significant among
men in charge of meals (Supplementary Table 3, Model
2). Another possible explanation for the association between cooking skills and underweight is that cooking
skills may be a surrogate indicator of physical capacity indaily living. To examine this hypothesis, we included
limitations in instrumental activities of daily living status[49, 50] in our model as a confounding factor, confirming that the ARRR of underweight remained significant(Supplementary Table 3, Model 3). Contrary to expectations, a low level of cooking skills was associated with
underweight but not with obesity among older adults.
For Asian people, underweight is a consistent risk factor
for death, and this risk is higher than that associatedwith obesity [51]. Underweight has also been reported to
be associated with frailty [52], fracture, and bone loss[53], which are critical obstacles to maintaining qualityof life among older people [54, 55]. Therefore, it may be
important for health policy makers to identify people
with poor cooking skills and organize programs to enhance cooking skills to prevent underweight.
The association between cooking skills and underweight was especially prominent among men in charge

Tani et al. International Journal of Behavioral Nutrition and Physical Activityof meals, and this association remained significant in thisgroup even after accounting for limitations in instrumental activities of daily living, frequency of home cooking,and vegetable/fruit intake (Supplementary Table 3, Model
4). This finding is plausible because many men have family
members—often their wives—who prepare meals forthem. Among the men in our study sample, 74% reported
that a family member prepared their daily meals (Table 1).
Considering that many men in charge of meals arewidowed or divorced (Supplementary Table 2), these men
may have difficulty preparing meals because they had few
opportunities to prepare meals before losing their spouse.
These men may thus be less motivated to cook and to eat,which can lead to a lower appetite [56]. Additionally, appetite decreases with age, and poor appetite has beenshown to be related to, for example, lower intake of energy, protein, and vegetables/fruits; lower dietary diversity[57, 58]; and higher risks of malnutrition [59] and mortality [58]. Further studies are needed to examine the potential mechanisms of the risk of underweight caused by low
levels of cooking skills for men. About half of older Japanese men who cook at home started cooking when they
were over 50 years old [60]. Considering that cooking classes for men have increased over the past few decades inJapan, intervening at an older age may be feasible andacceptable.
This study had several limitations. First, we used selfreported weight and height to calculate BMI, which may
have led to an under- or over-estimate of BMI [61]. A
previous study demonstrated that, when calculated fromself-reported weight and height, the BMI of older Japanese people was underestimated, compared with objective measures of weight and height; however, the same
study showed that the BMI of underweight men andwomen was overestimated by 0.7 and 0.3, respectively,
because these groups tended to over-report their weight[62]. Therefore, we may have underestimated the association of cooking skills with underweight. Second, we defined home cooking simply, excluding only the
preparation of ready-to-eat food. Therefore, people who
cooked low-quality meals or used some prepared foodsin their cooking may have been included in the high frequency of home cooking category. This may have led toan underestimate of the association of cooking skills
with low frequency of home cooking. Third, frequency
of vegetable/fruit intake was assessed using a single, simple item. Future studies should use more detailed questions to assess which food groups are associated cooking
skills. Fourth, we observed a ceiling effect for women’scooking skills, as has been reported in a previous study
using the original cooking scale [9]. Considering the reduction in the available time for cooking in recent years,
it may be beneficial to investigate cooking skills not onlyin terms of methods (e.g., boiling and stewing), but also(2020) 17:82

Page 10 of 12

in terms of the ability to prepare a variety of meals in ashort time. Moreover, a thorough psychometric assessment of the modified cooking scale should be performed
if it continues to be used. More comprehensive, validated measures for assessing food and cooking skill confidence are now available [63]. Therefore, it is possible
to use these measurement methods in the future. Fifth,
we could only evaluate a limited number of eating behaviors. Future work should examine associations between cooking skills and other aspects of diet, such as
dietary pattern, food components, and portion size, tounderstand the mechanisms of the relationship between
cooking skills and weight status. Sixth, because the municipalities that participated in the JAGES survey were
not randomly selected, the generalizability of our findings to other populations in Japan is limited. Finally, because this study was cross-sectional, we could not assesscausality: Reverse causation is possible, and unmeasured
factors such as personality may confound the examinedassociations. For example, underweight may be accompanied by frailty or low muscle strength, which may
make it difficult to cook some foods or to cook for along time while standing, resulting in low confidence in
one’s cooking skills. However, more than half of theadult respondents in a previous study said that they hadlearned most of their cooking skills when they were
teenagers and that they had learned these cooking skills
mainly from their mothers [64]. Future randomized controlled trials comparing cooking, eating behaviors, andweight status among older adults with and without
cooking skills interventions would clarify the causal
association.

Conclusions
Using a large-scale cross-sectional study, we confirmedthat women had higher levels of cooking skills than did
men and that the associations of cooking skills with dietary behaviors and weight status differed by gender.
Moreover, the associations of cooking skills with unhealthy dietary behaviors and weight status were especially pronounced among men who were in charge ofmeals. Considering the possibility that the person in
charge of meals may change in older age, research on
support to improve cooking skills among older people isneeded.
Supplementary information
Supplementary information accompanies this paper at https://doi.org/10.
1186/s12966-020-00986-9.
Additional file 1: Table S1. Adjusted relative risk ratios of underweight
and overweight according to the cooking skills of older Japanese men(n=9,143) and women (n=10,595). Table S2. Characteristics of older
Japanese men by cooking responsibility status (n = 9,203). Table S3.

(2020) 17:82

Tani et al. International Journal of Behavioral Nutrition and Physical Activity

Adjusted relative risk ratios of underweight by cooking skill among older
Japanese men.

4.

Abbreviations
CI: confidence interval; BMI: body mass index; JAGES: Japan Gerontological
Evaluation Study

5.

Acknowledgments
We are particularly grateful to the staff members in each study area and in
the central office for conducting the survey.
Authors’ contributions
YT conceived the design, analyzed the data, reviewed the literature, andwrote the first draft of the article. KK collected the data. TF revised the firstdraft. KK edited the manuscript. All authors approved the final version of themanuscript.
Funding
This study used data from the JAGES, which was supported by a Japan
Society for the Promotion of Science KAKENHI Grant (JP15H01972, 20H00557
and 19 K14029), a Health Labour Sciences Research Grant (H28-Choju-Ippan002, H30-Junkanki-Ippan-004, 19FA1012 and 19FA2001), grants from theJapan Agency for Medical Research and Development (JP18dk0110027,
JP18ls0110002, JP18le0110009, JP19dk0110034 and JP20dk0110034), Research
Funding for Longevity Sciences from National Center for Geriatrics and Gerontology (29–42), and a JST-OPERA program grant (JPMJOP1831).
Availability of data and materials
The datasets used and analyzed in the current study are from the JAGES
study. All enquiries are to be addressed to the JAGES data management
committee via e-mail: dataadmin.ml@jages.net. All JAGES datasets have
ethical or legal restrictions for public deposition because of the inclusion ofsensitive information from the human participants.
Ethics approval and consent to participate
The JAGES participants were informed that participation in the study was
voluntary and that completing and returning the questionnaire via mailindicated their consent to participate in the study. The JAGES protocol wasapproved by the Ethics Committee in Research of Human Subjects at the
National Center for Geriatrics and Gerontology (No. 992) and Chiba
University Faculty of Medicine (No. 2493).
Consent for publication
Not applicable.

6.

7.

8.

9.
10.

11.

12.

13.
14.
15.
16.
17.
18.
19.

20.

21.
Competing interests
The authors declare that they have no competing interests.
Author details
1
Department of Global Health Promotion, Tokyo Medical and Dental
University (TMDU), 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.
2Center for Preventive Medical Sciences, Chiba University, 1-8-1 Inohana,Chuo-ku, Chiba-shi, Chiba 260-8672, Japan. 3Department of Gerontological
Evaluation, Center for Gerontology and Social Scienc, National Center for
Geriatrics and Gerontology, 7-430 Morikoka-cho, Obu-shi, Aichi 474-8511,
Japan.

22.
23.

24.
25.

Received: 20 November 2019 Accepted: 18 June 2020
26.
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