United States 

Department of 

Agriculture

Economic

Research

Service

Economic

Information

Bulletin

Number 83

September 2011

How Americans Rate Their Diet 

Quality: An Increasingly Realistic 

Perspective

Christian Gregory

Travis Smith

Minh Wendt
United States

Department

of Agriculture

www.ers.usda.gov

A Report from the Economic Research Service

Abstract

Over the last 20 years, awareness of diet-related health concerns has become widespread 

in the United States as obesity, along with its associated human and financial costs, has 

increased. To estimate how this awareness affects Americans’ perceptions of their own 

diet quality over this period and the factors associated with self-assessed diet health, we 

examine data from both the 1989-91 Continuing Survey of Food Intakes of Individuals 

and the 2005-08 Flexible Consumer Behavior Survey module of the National Health 

and Nutrition Examination Survey. We find, first, that Americans have become much 

less likely to rate their diets as “Excellent” or “Very Good” in terms of healthfulness, 

even though the healthfulness of the American diet has undergone little change over this 

period. Second, current self-ratings of diet are inversely related to the frequency of fastfood and food-away-from-home consumption and positively related to the frequency of 

sharing meals with family. In addition, self-ratings of diet are positively associated with 

household availability of dark green vegetables and low-fat milk and negatively associated with availability of sweetened soft drinks.

Keywords: Diet perceptions, nutrition information, consumer perceptions, diet rating, 

CSFII, NHANES, FCBS

Christian Gregory

Travis Smith

Minh Wendt

How Americans Rate Their 

Diet Quality: An Increasingly 

Realistic Perspective

Economic

Information

Bulletin

Number 83 

September 2011
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Contents

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Changes in Self-Assessed Diet Quality . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Diet Perception, Food Away From Home, and Food Expenditures . . . . 8

Food Preparation and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
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Summary

What Is the Issue?

An obstacle to policies aimed at improving diets through education is that 

consumers tend to overrate the quality of their diets and to think that dietary 

guidelines are directed at others, not themselves. In this study, we look at the 

change in Americans’ subjective perceptions of their diet quality between 

1989-91 and 2005-08. These changes provide a snapshot of consumers’ 

increased dietary realism and, perhaps, receptiveness to dietary guidance, 

and they also suggest the possibility that a changed information environment has affected consumers’ perception. In addition, we use data from the 

ERS-supported Flexible Consumer Behavior Survey (administered with the 

National Health and Nutrition Examination Survey (NHANES)) to highlight 

how perceptions of diet quality vary with food expenditures, household food 

availability, and eating behavior.

What Did the Study Find?

Although the actual healthfulness of diets has not changed much in the last 

15 years, there has been a large and significant decrease in the percentage of 

Americans who rate their diets as Excellent or Very Good. 

•	The share of people who said that their diets were excellent or very

good declined by 9.1 percentage points, from 41 percent to 31.9 percent, 

between 1989-91 and 2005-08.

•	Declines in the share of excellent or very good self-ratings of diet were

especially large among Hispanics and people who were underweight, 

overweight, or obese, younger than 65, or had some college education 

(but not a college degree).

•	People who perceived themselves as overweight became less likely to

rate their diet as excellent or very good between 1989-91 and 2005-08.

•	Those who had diets high in fat were much less likely to rate their diets

as very good or excellent in 2005-08 than in 1989-91.

These results suggest a reduced optimistic bias in Americans’ views of their 

diets—and perhaps greater receptiveness to information about the relationships between diet and health. 

We also find a strong relationship between diet assessment and some dietary 

choices and habits. Comparing subjective ratings of diet quality across 

different groups, we find: 

•	Self-ratings of diet healthfulness tend to be low among people who report

a higher share of their food budget spent away from home and of calories 

eaten away from home.

•	Those with better diet self-ratings are more likely to share meals with the

family, both at home and away from home.
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•	Those who report high diet quality are more likely to keep skim milk and

dark green vegetables on hand in the household, and they are less likely 

to stock sugar-sweetened beverages.

How Was the Study Conducted?

The data for our comparisons of diet quality perception come from the 

1989-91 Continuing Survey of Food Intakes of Individuals (CSFII) and 

the 2005-2006 and 2007-2008 waves of the National Health and Nutrition 

Examination Survey (NHANES). The CSFII is also our source for data on 

household food expenditures in 1989-91. The 2007-08 NHANES data on 

diet quality perceptions, food-away-from-home frequency, household food 

expenditures, the kinds of food kept at home, travel time to the grocery store, 

and social context of eating come from the Flexible Consumer Behavior 

Survey (FCBS) module sponsored by the Economic Research Service. The 

2005-06 NHANES included a subset of FCBS questions, including diet 

quality perception and food-away-from-home frequency. For these questions, 

we report results from the combined 2005-08 NHANES data. 
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Introduction

Over the past 20 years, changes in food markets and food production technology, as well as the dramatic increase in obesity prevalence, have brought 

America’s eating habits into sharp public focus. Americans, we now know, 

eat diets that are too high in calories, fats (especially saturated fats), sodium, 

and added sugar. Our diets are also too low in fiber, whole grains, fresh vegetables, and important nutrients. The effects of our dietary habits are partly 

borne out by the health costs attributable to obesity which, by one calculation, were $85 billion in 2006 (Finkelstein et al., 2009). These effects are 

also felt in the reduced productivity and quality of life that come with health 

conditions associated with obesity. 

Although health researchers now know a great deal about the quality of 

American diets, consumers’ perceptions of their diets are often inaccurate. 

Research has shown that consumers tend to perceive that their diets are better 

than they are relative to widely accepted dietary guidance. For example, 

Glanz et al. (1997) showed that consumers had difficulty estimating the 

amount of fat in their diets: more than a fourth of American consumers in 

Glanz’s study underestimated their fat intake, and an even larger fraction of 

Dutch participants did so. Variyam, Shim, and Blaylock (2001) found that 40 

percent of U.S. household meal planners surveyed in 1989-90 judged their 

diet to be of higher quality (in terms of healthfulness) than could be justified using a standard rubric, the USDA’s healthy eating index (HEI). In the 

1989-91 Continuing Survey of Food Intakes of Individuals (CSFII), respondents who got more than half of their daily calories from fat were nearly 

twice as likely to rate the healthfulness of their diets as Excellent compared 

with those with lower fat intakes.1 

This “optimistic bias” about diet is both an obstacle and an impetus for policy 

geared toward encouraging behavioral change through better information.2

On the one hand, such optimism might impede efforts to change behavior 

because it suggests that consumers see guidelines for diet improvement as 

directed toward others, not themselves. On the other hand, the optimism 

illustrates the need to understand how nutrition information is conveyed and 

received and, possibly, the need for more information about diet. 

This study is concerned with changes in diet perception because they offer 

us a window into changes in this optimistic attitude toward diet. Changes 

can offer a snapshot of consumers’ increased dietary realism and, perhaps, 

receptiveness to dietary guidance, and they also suggest the possibility 

that a changed information environment has affected consumers’ perception. To assess these possibilities, we examine how Americans’ evaluations of diet quality have changed over the period 1989-91 to 2005-08. We 

compare self-assessed diet quality reported in the 1989-91 CSFII with a 

similar measure collected in the 2005-06 and 2007-08 waves of the National 

Health and Nutrition Examination Survey (NHANES). We examine the 

way that changes in diet assessment vary across groups characterized by 

demographics, weight self-perception, and dietary intake. We also investigate how diet self-assessment varies with per capita food expenditures. We 

show that there is a strong relationship between diet assessment and some 

dietary choices and habits. In particular, consumption of food away from 

1Authors’ calculation from data 

described in this report.

2There is a large extant literature 

about “optimistic bias” with respect 

to food safety and health issues. In 

general, “optimistic bias” refers to the 

underestimation of defined risk, relative 

to peer groups directly or indirectly 

defined. For example, respondents in a 

survey might be asked about their perception of the risk of diabetes or heart 

attack relative to others of similar age. 

While self-assessments of diet health 

obviously imply defined risks and a reference point, the question in CSFII and 

NHANES about diet health does not 

specify either of these. We use the term 

“optimistic bias” here advisedly. See 

Miles and Scaife (2003) for a review of 

relevant literature.
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home (FAFH) and sharing meals in a family context seem strongly related 

to diet assessment. Moreover, reports in more recent data about the kinds 

of food stored at home are strongly related to diet assessment and suggest 

some familiarity with dietary guidance. Overall, we find that Americans have 

grown much more realistic (less optimistic) in their self-assessments of diet 

healthfulness in the 19 years covered by our data.

Data

The data we use come from two surveys: the 1989-91 CSFII and the 2005-06 

and 2007-08 waves of the NHANES. The samples from both of these data 

sets are drawn using complex, stratified designs, and both are weighted to 

be representative of the U.S. population.3 NHANES is currently the primary 

U.S. data set that continuously tracks information about diet, nutrition, and 

health outcomes for the civilian non-institutionalized population. NHANES 

oversamples low-income persons, adolescents 12-19 years of age, persons 

over 60 years of age, African Americans, and Mexican Americans. Although 

some of the content of the health modules does vary, basic information about 

diet intake, demographics, and income is constant over the 2005-06 and 

2007-08 waves of the data.

The 1989-91 CSFII was administered as two tandem surveys. One was the 

CSFII proper, which included a 3-day food and nutrient intake component 

for a total of over 11,000 respondents; the other was the Diet and Health 

Knowledge Survey (DHKS), which collected information on diet knowledge, attitudes, and perceptions from the approximately 6,000 meal planners/

preparers identified in the CSFII. The dietary intake component of the CSFII 

was folded into the NHANES in 2002, so the food intake data from the two 

surveys are in all important respects comparable. The 2007-08 NHANES 

included a supplementary module sponsored by USDA’s Economic Research 

Service, the Flexible Consumer Behavior Survey (FCBS). The FCBS 

collected data similar to that in the CSFII-DHKS, such as information on 

self-assessed diet quality and household food expenditures. The FCBS also 

included new questions on food-away-from-home frequency, family dining 

habits, household food stocking habits, and time used for shopping and 

cooking. While the full-blown FCBS was administered with the 2007-08 

NHANES, a subset of questions from it, including questions on diet quality 

perception, were included in the 2005-06 NHANES. 

We use data from the CSFII 1989-1991 and NHANES 2005-2008 to make 

comparisons of self-assessed diet quality, energy and nutrient intake, and 

income; in addition, we have information in all these years on whether 

intakes are from food at home (FAH) or food away from home (FAFH). As 

a result, analysis of the share of calories from FAFH makes use of all years 

in the data. Our comparisons of self-assessed diet quality by per capita food 

expenditure use the CSFII data and NHANES 2007-08, since expenditure 

data are only available in those years. Finally, data about frequency of eating 

FAFH or fast food away from home, availability of foods in the home, travel 

time to the grocery store, and the frequency of eating in a household setting 

come from the FCBS in the 2007-08 NHANES.

For this study, we limit the sample to respondents who are at least 20 years 

old and have completed a full complement of dietary intake diaries for each 

3All our estimates take into account 

the complex sample design.
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survey.4 In the 1989-91 CSFII, we impose the additional constraint that the 

sample person be the respondent to the diet intake survey.

Changes in Self-Assessed Diet Quality

In each of the surveys we use, respondents were asked to appraise the overall 

healthfulness of their diets.5 The choices offered were “Excellent,” “Very 

Good,” “Good,” “Fair,” and “Poor.” For the population as a whole and for 

women and men, the percentage of persons who said that their diet was 

Excellent or Very Good declined between the two surveys; for the entire 

population, the percentage of people who rate their diets as Excellent or 

Very Good fell by 4.6 and 4.5 percentage points, respectively. For men, the 

declines were 8.5 and 2.0 percentage points, and for women, 3.3 and 5.1 

percentage points, respectively (table 1).6

The decline in the likelihood of reporting an Excellent or Very Good diet 

was shared over most demographic groups. Large decreases were seen for 

respondents of Hispanic origin, those with household incomes between 130 

and 300 percent of poverty, and those who had some college education (but 

not a college degree).7 Interestingly, people who were underweight, overweight, or obese became less likely to rate their diets as Excellent or Very 

Good compared with those of normal weight (fig. 1).8 In addition, there was 

no strong change in the likelihood of rating one’s diet as Excellent or Very 

Good for low-income people, who are generally less likely to rate their diets 

as Excellent or Very Good: 34 percent of people below 130 percent of the 

poverty line rated their diet as Excellent or Very Good in 1991, as opposed to 

44 percent of those above 300 percent of the poverty line.

These broad and significant changes in diet perception could happen for two 

reasons. First, diets might indeed have worsened between these two surveys, 

with the self-evaluations reflecting this fact. Second, it could be that diets 

have not changed, but that people exhibit marginally less optimistic bias in 

4For the CSFII, there were 3 days of 

intake survey; for NHANES, 2 days. In 

the CSFII, we retain only those persons 

who responded themselves to the intake 

surveys, which contain the assessment 

of diet.

5In NHANES, respondents are asked 

“In general, how healthy is your overall 

diet?” In CSFII, the prompt for the respondent is, “In general, would you say 

the healthfulness of your diet is Excellent, Very Good, Good, Fair or Poor?”

6The summary measures calculated 

here rely on sampling weights and 

variance units constructed by NHANES 

(see CDC (2005) for more on the construction of weights and variance units). 

We estimate means and proportions by 

the formula

1

1

,

n

i i i

n

i i

w x

x

w

=

=

∑ =

=

∑ =

where w and x are sample weights and 

values of the random variable of interest. We calculate the variance of the 

means using Taylor series linearization. 

For a sampling design like NHANES, 

we estimate the variance of a random 

variable, x, by

2

1 1 1

2

1 1 1

( ) ( ) 1

( ) , 1

h

h hi

L n h

h h h i h

L n m hi

hij hi h i j hi

n

v x x x

n

m

x x

m

= =

= = =

= ∑ ∑ − + −

∑ ∑ ∑ − −

where h indexes the number of strata, i

indexes primary sampling units within a 

strata, and j indexes household clusters 

sampled within PSUs; xhi and xhij are 

the PSU-level and cluster-level totals 

and i x and x h h are the strata and PSUlevel means of the random variable x. 

The total variance of x is the sum of the 

within-strata and the within-PSU 

variance of x. 

7Decreases are calculated as 

P(Excellent/Very Good|CSFII)-

P(Excellent/Very Good|NHANES). 

Significance is determined using a 

conventional t-test for the difference 

between proportions.

8We use conventional definitions of 

body mass index: BMI < 18.5 = underweight; 18.5 < BMI < 25 = normal 

weight; 25 < BMI <30 = overweight; 

BMI > 30 = obese. Unless otherwise 

noted, all changes are statistically significant at p<.05.

Table 1

Self-assessed diet quality, 1989-91 and 2005-08

Population N

Excellent Very Good Good Fair Poor

All 1989-91 5,655 13.2 27.8 39.3 15.5 4.2

All 2005-08 12,669 8.6 23.3 40.7 21.2 5.8

% Change -4.6 -4.5 1.3 6.2 1.6

Men 1989-91 1,117 16.7 25.3 32.5 17.8 7.7

Men 2005-08 6,188 8.2 23.3 40.4 22.2 5.9

% Change -8.5 -2.0 7.9 4.4 -1.8

Women 1989-91 4,538 12.3 28.4 41.2 14.9 3.3

Women 2005-08 6,481 9.0 23.23 40.9 21.3 5.6

% Change -3.3 -5.1 -0.3 6.3 2.3

Cells show percentages of sample that report given levels of diet healthfulness. All calculations account for sample design. Source: Authors’ calculations based on CSFII 1989-91 and 

NHANES 2005-08 data.
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All differences are significant at least at p<.10. 

Source: Authors’ calculation based on CSFII 1989-91 and NHANES 2005-08.

Figure 1

Change between 1989-91 and 2005-08

Race/Ethnicity

Hispanic White Black Other

-30

-20

-10

0

<130% Poverty 130−300% Poverty >300% Poverty

-15

-10

-5

0

HS Dropout HS Grad Some College College Grad

-20

-15

-10

-5

0

Underweight Normal weight Overweight Obese

-15

-10

-5

0

20−34 35−49 50−64 65 & up

-20

-10

0

10

Percentage point change: Excellent or Very Good diet

Income

Percentage point change: Excellent or Very Good diet

Age

Percentage point change: Excellent or Very Good diet

Body Mass Index Status

Percentage point change: Excellent or Very Good diet

Education

Percentage point change: Excellent or Very Good diet
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their evaluations of their diets; this could also imply that they are becoming 

more receptive to dietary guidance.

Previous research has shown that the quality of American diets did not 

change much over the period in question, at least as measured by the 

Healthy Eating Index (HEI). The HEI is a benchmark constructed by the 

USDA to measure diet quality alongside the recommendations in the 

Dietary Guidelines for Americans and the Food Guide Pyramid (replaced 

by MyPlate). An HEI score above 80 is considered “Good,” while scores 

between 51 and 80 indicate a diet that “needs improvement,” and scores 

below 51 suggest a diet that is “Poor.” The HEI has had two iterations: 

before the 2005 Guidelines, it was constructed on the basis of 10 components, and since then it has been constructed on the basis of 12 components 

that better accommodate changes to the 2005 Guidelines. While it would be 

best to compare HEI scores for 1989-91 and 2005-08, the latter scores are not 

yet available. Other comparisons, however, yield fairly convincing evidence 

that diet healthfulness didn’t change much between these surveys. Studies 

using the CSFII waves from 1989-1990 and 1994-96 and the 10-component 

score found that the average HEIs for these years were virtually indistinguishable from each other. Both years had average scores between 63 and 64 

out of a possible total index score of 100 (Bowman et al., 1998; Center for 

Nutrition Policy and Promotion, 1995). Subsequent studies using the 2005-

basis (12-component) score and data from the 1994-1996 CSFII and 2003-04 

NHANES similarly found HEI scores basically unchanged at around 58 

(Guenther et al., 2007; CNPP, 2008; see also Variyam and Smith, 2010).9

The fact that—with different component scales—the 1994-96 HEIs were 

identical to both 1989-90 and 2001-02 HEIs suggests that the general healthfulness of the American diet has not changed very much over the last 15 or 

20 years.

There is an important caveat to this characterization of the American diet, 

however. All of the component scores for the HEI—and thus the overall 

score—are calculated on a per 1,000-calories-of-intake basis. (The recommended amounts are normalized for age groups, so that children and seniors 

are not assumed to need the same intakes.) With this method, the healthfulness of an actual level of intake (3,500 calories as opposed to 2,500, for 

example) does not contribute one way or the other to the HEI. From one 

point of view, that is sensible, since we do not know much about what “overeating” may be for any given person.10 On the other hand, we do know that 

eating more than one expends in energy will lead to weight gain, no matter 

how “healthy” the calories are. The increased prevalence of overweight and 

obesity in the United States—along with related conditions, such as diabetes 

and heart disease—suggests that caloric intake is out of balance with energy 

expenditure, quite generally speaking. This is not accounted for in the HEI.

Notwithstanding this omission from the HEI formula, however, there is 

little evidence that caloric intake affects how consumers evaluate their diets. 

Table 2 shows levels of caloric intake conditional on self-assessed diet in 

the CSFII and NHANES. Although caloric intake is higher on the whole in 

the NHANES data, the differences in the changes in intake from one survey 

to another are only marginally significant for those who rated their diets as 

Very Good, Good, or Fair relative to those who rated their diets as Excellent. 

In other words, despite the fact that those with Poor diets showed a bigger 

9In addition, the same proportion 

of Americans had HEI scores high 

enough to indicate a good diet—about 

12 percent—in 1989-91, 1994-96, and 

2001-2002. That proportion was about 

10 percent in 1999-2000. See Bowman (1998), CNPP (1995), and CNPP 

(2002); scores for 2001-2002 from 

authors’ calculations using data found 

at http://www.cnpp.usda.gov/HealthyEatingIndex-Archive.htm.

10HEI scores do take age into account 

in establishing appropriate consumption 

amounts.
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increase in calorie intake over the period, there is no statistical evidence that 

this increase is different from the other diet-rating categories. So the omission of calorie levels from the HEI, while perhaps important for the evaluation of the health of a diet, does not seem to affect our interpretation of the 

change in self-assessment of diets. For the things that are measured by HEI, 

there is little or no change; for caloric intake, which is not measured by HEI 

but for which there is change, there doesn’t seem to be much association with 

changes in self-rated diet.

Given this data, it could be that Americans have become more aware of 

what constitutes a healthy diet and more receptive to dietary guidance. 

Indeed, other research shows that Americans have become more aware of 

Government information sources for healthier diets. According to Variyam 

and Smith (2010), 51 percent of Americans had heard of the Dietary 

Guidelines in 2005-06, as opposed to just 30 percent in 1994; similarly, 79 

percent had heard of the Food Guide Pyramid in 2005-06, while only 33 

percent were familiar with it in 1994. 

There are other signals in the data that Americans are becoming aware of 

the shortcomings of their dietary habits. For example, people who had highfat diets, who thought they were overweight,11 and who got at least a third 

of their daily energy from food away from home (FAFH) all showed better 

recognition of diet healthfulness in later years compared with the earlier 

survey years (fig. 2).12 Among those who had a high-fat diet, the decline 

in the percentage who rated their diet as Excellent or Very Good was 14.5 

points. Among those who thought of themselves as overweight, there was a 

12-percentage-point decline. For those who got at least a third of their energy 

from food away from home, the decrease was 7 percentage points.

11Respondents were asked if they 

thought they were “overweight, underweight, or about right.”

12For the purposes of this calculation, 

we defined a high-fat diet as one in 

which at least half of all energy intake 

was from fat.

Table 2

Total caloric intake by self-assessed diet quality

Total caloric intake

Survey Excellent Very Good Good Fair Poor

CSFII 1,721 1,659 1,710 1,756 1,744

NHANES 2,106 2,231 2,252 2,320 2,381

Change 385 573* 542* 564* 638

*Changes relative to Excellent category significant at p<.10. Other differences are insignificant. 

Source: Authors’ calculation based on CSFII 1989-91 and NHANES 2005-08. 
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FAFH = Food Away From Home. Differences between years are significant at p<.01.

Source: Authors’ calculations based on Continuing Survey of Food Intakes of Individuals 

1998-91 and National Health and Nutrition Examination Survey 2005-08 data. 

Figure 2

Changes in self-assessed diet quality by self-perceived weight,

calories from FAFH, and calories from dietary fat

Changes in self-assessed diet quality by self-perceived weight status

Changes in self-assesed diet quality among those with a high-fat diet

Changes in self-assessed diet quality by food away from home

Excellent/VG Good Fair/poor

39%

28%

38%

43%

23%

29%

I’m overweight, 1989-91

I’m overweight, 2005-08

Excellent/VG Good Fair/poor

43%

29%

38%

44%

19%

27%

High-fat diet, 1991

High-fat diet, 2008

Excellent/VG Good Fair/poor

37%

30%

39% 43%

24% 27%

More than 1/3 energy

FAFH, 1989-91

More than 1/3 energy

FAFH, 2005-08
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Diet Perception, Food Away From Home, 

and Food Expenditures

Conventional wisdom suggests that better diets cost more, and it is not a 

stretch to think that the converse proposition—that spending more might 

secure a better diet—is also widely assumed by consumers. But could the 

changes in overall diet assessment shown above reflect this belief? For this 

to be true, we would have to observe a growing expenditure-based disparity 

in self-assessment of diet; that is, we would have to see the expenditure 

threshold for “Excellent” or “Very Good” diets increase substantially in 

NHANES relative to CSFII. 

To examine the role of food expenditures on diet assessment, we used data 

in the 1989-91 CSFII and the last 2 years of NHANES data available, 2007-

2008.13 Data about expenditures in these years are on a household basis; we 

calculate expenditure on a per capita basis by dividing total expenditure by 

the size of the household. We also use the survey distinction between food 

purchased at a grocery or specialty foods store and food purchased and eaten 

away from home to find FAFH expenditure.

Interestingly, there is little difference in food expenditure between those who 

rate their diets as Excellent and those who rate them as Poor in either wave 

of our data. In 1989-91, for example, the difference in per capita monthly 

food expenditures between these two groups is only $24. While this difference is statistically significant, the former group also spent significantly more 

than all others, including those who said their diet was Very Good or Good. 

At the same time, those with Very Good or Good diets spent essentially the 

same amount on food as those with Fair or Poor diets. Thus, in 1989-91, the 

primary difference was between those with Excellent diets and everyone else. 

In 2007-08, the difference in expenditure between diets rated Excellent and 

Poor was only $18. This difference is not statistically significant (fig. 3). All 

13As explained above, data on household food expenditures are not available 

in the 2005-06 wave of NHANES.

Expenditures deflated to 2008 dollars using the CPI. Differences between those who rate their 

diet "Excellent" and all others are significant in 1989-91 at p<.05; other differences are not 

significant.

Source: Authors’ calculations using Continuing Survey of Food Intakes of Individuals 1989 and 

National Health and Nutrition Examination Survey 2007-08 data. 

Figure 3

Per-capita food expenditures, by self-assessed diet quality, 

1989-91 and 2005-08 

Dollars

1989-91 2007-08

0

50

100

150

200

250

300

Excellent Very Good Good Fair Poor
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of this indicates that the decrease over time in the likelihood of rating one’s 

diet as Excellent or Very Good is likely not related to an increased difference in food expenditures between those who have relatively high (Excellent, 

Very Good) ratings of their diets and those who do not.

However, there is a clear relationship between household financial resources 

and diet perception.14 As we might expect, people who rate their diets as 

Excellent tend to come from households with greater financial resources 

than those who rate their diet as Poor. This difference is more pronounced 

for 1989-91 than for 2005-08. In the earlier years, income decreases more or 

less incrementally with diet rating: those who rate their diets as Very Good 

in general have less income than those who rate their diets as Excellent, 

while those rating their diets as Good have less income than those rating diet 

Very Good, and so on. In the later years, the primary difference in household 

income is between those who rate their diets as Good or better and those 

who rate them as Fair or Poor. This may suggest that, in more recent years, 

income does less to explain diet rating, except in the very tails of diet distribution (fig. 4).

Another aspect of diet behavior that could be related to changes in perception is the increased reliance on food away from home over the last 20 years. 

Foods that are produced in restaurants, convenience stores, and specialty 

stores are generally thought to be less healthy than foods prepared at home 

and so are a cause of concern to nutritionists and health policymakers. As 

Todd, Mancino, and Lin (2010) have shown, consumption of an extra meal 

away from home each week significantly increases calories and lowers servings of fruit, vegetables, and whole grains per 1,000 calories consumed. (See 

also Lin, Guthrie, and Frazao, 1999.) As we know, however, Americans have 

made FAFH an ever larger part of their diets. According to our data, between 

14Data on income are available in all 

NHANES years.

1989 2007

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

Differences between non-adjacent categories are all significant at p<.05. Household income 

deflated to 2008 dollars using the Consumer Price Index.

Source: Authors’ calculations using Continuing Survey of Food Intakes of Individuals 1998 

and National Health and Nutrition Examination Survey 2005-08 data.

Figure 4

Household income by self-assessed diet quality 

Dollar

Excellent Very Good Good Fair Poor
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1989-91 and 2007-08, the fraction of daily calories from FAFH increased 

from about a quarter to more than a third. The fraction of total household 

food expenditures on FAFH increased from 21 to 26 percent (table 3).15

An interesting aspect of the dependence on FAFH is its strong correlation 

with diet perception. Even more striking is the distinction that consumers 

draw between food away from home and fast food away from home. As 

noted, FAFH is generally of lower quality than food prepared at home. 

Consumers recognize this: in the most recent data, people who rate their 

diet as Excellent eat food prepared away from home, on average, a little 

over three times per week, while those who rated their diets as Poor ate food 

away from home nearly six times per week. Fast food, which is believed to 

be of lower quality than FAFH in general, is even more strongly associated 

with perceived diet quality in our data.16 While those who rate their diet as 

Excellent eat fast food less than once a week, those who give their diet a Poor 

rating eat fast food about three times as often (fig. 5).17 This suggests that 

consumers understand both the relative quality of FAFH compared with food 

prepared at home and the deleterious effects of fast food on diet quality.

In addition to eating FAFH more frequently, people who rate their diets as 

Poor come from households that spend a larger fraction of their food budgets 

on FAFH than people who say they have healthier diets.18 For example, in 

2007-08, people with Poor diets spent 29 percent of their food budgets on 

FAFH, while those rating their diets as Excellent spent 22 percent. People 

rating their diets as Poor also get a higher share of their total energy intake 

from FAFH. In the same year, people with Poor and Excellent diets got 39 

and 26 percent of their calories from FAFH. The ratio of the share of calories 

from FAFH to the share of expenditures on FAFH is generally higher for 

those with Poor-rated diets. That is, people with Poor-rated diets get more 

calorie bang for the FAFH buck than those with better rated diets (fig. 6). 

One reason that nutritionists and health policymakers are interested in FAFH 

intake is that it can be a source of “cheap calories” without much nutritional 

value. But is the relative cost of calories associated with diet assessment? 

That is, do people associate calorie cost with healthfulness of diet, regardless 

of food source?19

The short answer to this question is, “Not really.” In both waves of the 

survey, there is an association between calories per dollar and diet assessment, although not a strong one. For example, in 1989-91, respondents who 

15The levels reported here differ 

from those developed by Clauson and 

Leibtag (2008); they report that FAFH 

consumption was 37.6, 37.2, and 37.3 

percent of total expenditure in 1989, 

1990, and 1991, and that it was 41.5 

percent in 2007 and 2008. The difference in the levels of their estimates and 

ours are no doubt due to important differences in our data sources and what 

is counted: Clauson and Leibtag (2008) 

use data from Department of Commerce Census of Retail Trade—i.e., establishment data, instead of the household data we use here. In addition, 

their expenditure measure includes food 

eaten at schools and colleges as well as 

any food provided to domestic military 

personnel. It is interesting to note that, 

despite the differences in the fraction 

of expenditure on FAFH between those 

results and ours, the increase between 

the two periods in FAFH expenditure is 

very similar at between 4 and 5 percentage points.

16It is not clear that fast food is 

significantly worse than food prepared 

at restaurants, although it is frequently 

portrayed this way in the media and 

trade press; “fast food” has become 

shorthand for all food away from 

home in many contexts. On the relative 

healthfulness of fast food and other 

FAFH, see Guthrie, Lin, and Frazao 

(2002), table 1. Also see Binkley 

(2008).

17Both differences between groups 

are significant at p<.01. All other differences for nonadjacent diet categories 

are also significant at p<.01.

18The figures show this on a per 

capita basis.

19Food expenditures are collected on 

a monthly household basis; we divide 

by size of household to get per capita 

monthly expenditure. Food intake is 

collected on a per person daily basis; in 

order to calculate calories/dollar spent, 

we divide per capita monthly expenditure by 30 and then take the ratio of 

daily intake by this normalized expenditure measure. Results are insensitive 

to excluding persons who claim that 

they ate less or more than usual on the 

day in question.

Table 3

Increased reliance on food away from home, by sample year

Percent of calories FAFH Percent of expenditures FAFH

CSFII 24.0 21.5

NHANES 05-08 34.6 26.2*

Change 10.6 4.7

FAFH = Food Away From Home. 

Between-year changes are significant at p<.01. 

*Data on percent expenditures FAFH available only in NHANES 2007-08. 

Source: Authors’ calculations based on Continuing Survey of Food Intakes of Individuals 

1989-91 and National Health and Nutrition Examination Survey 2005-08 data.
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got the most calories per dollar were those who rated their diets as Good; the 

most evident difference in energy per dollar is between those who rate their 

diets as Excellent and everyone else. In 2007-08, those who rated their diets 

as Fair or Poor got more calories/dollar than those with Excellent or Very 

Good diets, but these differences are not statistically significant (table 4).

FAFH = All food consumed away from home. 

Source: Authors’ calculations using National Health and Nutrition Examination Survey 

2007-08 data. 

Figure 5

Weekly FAFH and fast food frequency by self-assessed diet quality

Times eating FAFH/week

Times eating fast food/week

Excellent Very Good Good Fair Poor

3.2

3.8

4.4

5.1

5.8

Excellent Very Good Good Fair Poor

0.82

1.05

1.55

2.31

2.98
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*Data on percent of expenditures on FAFH available only in National Health and Nutrition 

Examination Survey 2007-08.

FAFH = All food consumed away from home. 

Source: Authors’ calculations based on Continuing Survey of Food Intakes of Individuals 

1989-91 and National Health and Nutrition Examination Survey 2005-08 data.

Figure 6

Percent of expenditures and calories FAFH

1989-91

2005-08

Excellent Very Good Good Fair Poor

0

5

10

15

20

25

30

35

40

Food expenditures FAFH*

Excellent Very Good Good Fair Poor

0

5

10

15

20

25

30

35

40

45

Food expenditures FAFH*

Calories FAFH

Calories FAFH

Percent

Percent

Table 4

Calories per dollar, by self-assessed diet quality

Self-assessed diet quality

Excellent Very Good Good Fair Poor

Calories/dollar 1989-91 247.5 283.0 296.0 280.6 282.4

Calories/dollar 2007-08 437.4 418.6 447.6 482.9 513.6

Differences between Excellent and all other categories are significant at least at p<.10 in 

1989-91. Differences between categories are statistically insignificant in 2007-08. 

Source: Authors’ calculations using Continuing Survey of Food Intakes of Individuals 1989-91 

and National Health and Nutrition Examination Survey 2007-08 data. 
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Food Preparation and Availability

Although the above evidence suggests that diet assessment is strongly negatively correlated with the frequency of FAFH consumption altogether, new 

data from the Flexible Consumer Survey module in NHANES qualifies that 

association. The data show that people who rate their diets as Excellent eat 

with their families more often than those who rate their diets as Poor. This 

is true both in general (i.e., including occasions with FAFH) and when we 

consider only occasions when meals are prepared and eaten at home. People 

who rate their diets as Excellent are also more likely to have someone in 

the household prepare dinner at home; this happens in households of people 

with Excellent diets between five and six times per week, but only four times 

per week for those rating their diets as Poor (table 5). This confirms earlier 

research that suggests that diet quality is strongly associated with eating 

meals with members of one’s family (Gillman et al., 2000) and with the 

mealtime environment in general (Boutelle et al., 2003; Nuemark-Sztainer et 

al., 2004).

The type of food that is stocked in the household is also closely associated 

with diet perception. People who said they always have low-fat or fat-free 

milk in their homes were significantly more likely to rate their diets as 

Excellent than those who never did. Similarly, those who reported always 

having dark green vegetables in the house were three times more likely to 

rate their diets as Excellent or Very Good than those who said they never 

kept them in the house. People who said they never had sugared soft drinks 

in the household were more likely to have Excellent or Very Good diets than 

those who always did (fig. 7).

A particularly interesting result drawn from these data is that diet assessment 

seems unrelated to travel time to the grocery store. Although we might think 

that those who rate their diets as less healthy would also be constrained in 

their food choices by their distance to supermarkets, the data suggest this is 

not the case. The travel time to the grocery store for all respondents in this 

survey is about 15 minutes, regardless of reported diet quality (fig. 8). This 

average time is the same as a national average reported by USDA (USDA, 

2009), but considerably less than this same study showed for low-income 

persons. This suggests that income alone—at least as it is reflected in travel 

time to the market—is not driving people’s evaluation of their diets. 

Table 5

Frequency of eating together, by diet quality

Excellent Very Good Good Fair Poor

Times cook & eat together 

at home per week 7.2 6.9 6.0 5.4 5.5

Times eat together per week 7.6 7.0 6.0 5.2 4.6

Times someone cooked 

dinner per week 5.5 5.3 5.0 4.7 4.1

Differences between those rating their diets as Excellent and Poor are significant at p<.05.

Source: Authors’ calculations using National Health and Nutrition Examination Survey 2007-08 

data. 
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All differences except those for those reporting Good diet health are significant at p<.01.

Source: Authors’ calculations using National Health and Nutrition Examination Survey 

2007-08 data. 

Figure 7

Self-assessed diet quality, food items stocked in household

People who always (never) have low-fat milk in the 

home report more (less) healthy diets

Consumers who always (never) have dark green vegetables 

in the home report more (less) healthy diets

Consumers who always (never) have sugar-sweetened soft drinks 

in the home report less (more) healthy diets

Excellent Very Good Good Fair Poor

10% 8%

29%

20%

41% 41%

18%

24%

3% 7%

Excellent Very Good Good Fair Poor

11%

3%

28%

11%

39%

35%

18%

32%

4%

20%

Excellent Very Good Good Fair Poor

8%

14%

19%

32%

42%

36%

24%

14%

7% 4%

Always have Never have

Always have Never have

Always have Never have
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Source: Authors’ calculations using National Health and Nutrition Examination Survey 2007-08 

data. 

Figure 8

Travel time to grocery store, by self-assessed diet quality

Travel time to grocery store, minutes

Excellent Very Good Good Fair Poor

14.4 13.2

14.5

16.2

14.9
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Discussion

Although the actual healthfulness of diets has not changed much in the last 

15 years, there has been a large and significant decrease in the percentage 

of Americans who rate their diets as Excellent or Very Good. These results 

may be good news for health policymakers, particularly those concerned with 

nutrition education. At the very least, these results suggest a reduced optimistic bias in Americans’ views of diet—and perhaps greater receptiveness 

to information about the relationships between diet and health. At best, the 

results suggest that Federal nutrition education efforts such as the Nutrition 

and Labeling Act, Supplemental Nutrition Assistance Program Education 

(SNAP-Ed), the Dietary Guidelines and MyPyramid.gov (now MyPlate.gov) 

have really made a difference in the way that Americans view diet quality. 

Our results from the recent Flexible Consumer Behavior Survey offer 

suggestive—though certainly not conclusive—evidence consistent with the 

latter view: households that always keep dark green vegetables and low-fat 

milk on hand are more likely to rate their diets as Very Good or Excellent 

than those that never do, and those that always keep sugared soft drinks on 

hand are less likely to report Excellent or Very Good diet ratings than those 

that never do.

The results we present are descriptive. They do not positively identify what 

is causing this change in diet perception. However, they do suggest avenues 

for further research. Most importantly, it would be helpful to know whether 

and to what degree nutrition information informs diet evaluations (such 

as reduced optimistic bias), and─especially─diet choices. This is particularly important for Federal nutrition education programs such as SNAP-Ed 

and Women, Infants, and Children (WIC) Nutrition Education, which are 

targeted towards those who, in general, have fewer resources to call upon 

in creating a healthy diet. The general question about what lies behind the 

change in diet perception is important in considering private sector actors, as 

well: the Affordable Care Act established regulations that require restaurants 

to publish nutrition information at the point of sale. Given our results with 

respect to FAFH, it will be important to know whether and how consumers 

use such information. 
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