RERF Report No. 17-15

A research paper published in the European Journal of Clinical Nutrition §Body composition and development of diabetes: a 15-year follow-up study in a Japanese
population
Yoshimi Tatsukawa, Munechika Misumi, Young Min Kim, Michiko Yamada, Waka Ohishi, SaekoFujiwara, Shuhei Nakanishi, Masayasu Yoneda
Eur J Clin Nutr 2018 (March); 72(3):374-80（doi: 10.1038/s41430-017-0077-7）

Study Findings
Following a Japanese population for an extended duration, this study reviewed theassociation of body composition with the development of diabetes, revealing that diabetes risk
differed depending on body fat distribution. It suggested that diabetes risk increases withincrease in trunk (abdominal) fat, but that, conversely, an increase in leg fat plays a preventive
role against diabetes.
Explanation
The body is composed mainly of fat, muscle, and bone, and dual-energy X-ray
absorptiometry (DEXA) examination allows measurement of body composition, including fat
mass and lean mass for the body as a whole and for specific regions (trunk, extremities, etc.).
This study reviewed the effects of body composition on the development of diabetes in theAdult Health Study (AHS) cohort of A-bomb survivors, which the Radiation Effects Research
Foundation (RERF) has followed for an extended duration through biennial healthexaminations to assess the health status of A-bomb survivors.
1. Study Purpose
Obesity is one of the major risk factors for diabetes, but not all obese people develop thedisease. Other than obesity, body composition, such as body fat distribution, is considered to
be one of the risk factors associated with diabetes. Only a limited number of studies, however,
have investigated the association between body composition and diabetes risk in Japanese andother Asian populations over a long duration in a longitudinal manner. The current study
reviewed the effects of body composition on the development of diabetes and determined
whether or not these effects differed with presence or absence of obesity.
2. Study Methods
We followed 1,532 diabetes-free subjects aged 48-79 years of age to detect new cases ofdiabetes until the end of 2011. The subjects had participated in the AHS over the 1994–1996
time period, undergoing whole-body DEXA examination for assessment of body composition.
To review body composition, we used fat mass amount and percentages for the trunk, legs,and arms as an indicator of body fat distribution. We calculated fat mass percentages for thetrunk, arms, and legs by dividing that body part’s fat mass by total soft tissue mass (i.e., totalmass minus bone mass). Furthermore, as an indicator of muscle mass, we used values
calculated by dividing appendicular (upper and lower extremities) lean mass (totalappendicular mass minus bone and fat mass) by the square of standing height.
The American Diabetes Association (ADA) recommends a body mass index (BMI) cut
point of 23 kg/m2 to identify diabetes risk in Asians, and we therefore defined
overweight/obesity as BMI≥23 kg/m2. Since body composition differs by sex, we analyzed
each sex separately, with adjustments performed for BMI, smoking status and alcohol
consumption, presence/absence of hypertension and dyslipidemia, baseline age categories,
and radiation dose.
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3. Study Results
1) Effects of body composition on the development of diabetes
In women, a positive association was suggested between the development of diabetes andtrunk fat mass/percentages (the higher the trunk fat mass/percentages, the higher thedevelopment of diabetes). However, a significant negative association was observed between
leg fat mass/percentages and the development of diabetes. That is, higher leg fat
mass/percentages indicated lower diabetes development. An analysis with adjustment fortrunk fat percentages (i.e., with trunk fat percentages assumed to be the same) revealed similar
results.
In men, separate analyses of trunk fat mass/percentages and leg fat mass/percentages inrelation to development of diabetes did not indicate a significant association in either case.
However, analysis that took into account trunk/leg fat percentages together revealed asignificant positive association between trunk fat percentages and development of diabetes, aswell as a significant negative association between leg fat percentages and development ofdiabetes, as was the case for women.
In both sexes, there was no significant association between development of diabetes andarm fat mass/percentages or appendicular lean mass.
2) Effects of body composition on development of diabetes in relation to the presence orabsence of overweight/obesity
Analysis that took into account trunk/leg fat percentages together revealed a significant
negative association between leg fat percentages and development of diabetes only inoverweight/obese groups (BMI≥23 kg/m2). However, a large difference in hazard ratios (riskratios) for development of diabetes was not observed with the presence or absence of obesity.
Furthermore, a significant negative association between appendicular lean mass (indicator ofmuscle mass) and development of diabetes was observed only in non-obese males (BMI<23kg/m2).
Study SignificanceDevelopment of diabetes was associated positively with trunk fat and negatively with leg
fat. Consequently, this study suggested that body composition assessment is one useful
method for detection of individuals at high risk for diabetes.
The Radiation Effects Research Foundation has studied A-bomb survivors and their offspring in
Hiroshima and Nagasaki for around 70 years. RERF’s research achievements are considered theprincipal scientific basis for radiation risk assessment by the United Nations Scientific Committee on
the Effects of Atomic Radiation (UNSCEAR) and for recommendations regarding radiation protection
standards by the International Commission on Radiological Protection (ICRP). RERF expresses its
profound gratitude to the A-bomb survivors and survivors’ offspring for their cooperation in ourstudies.
§The European Journal of Clinical Nutrition (EJCN) is an international, peer-reviewed journal covering all
aspects of human and clinical nutrition. The journal welcomes original research, reviews, case reports and briefcommunications based on clinical, metabolic and epidemiological studies that describe methodologies,
mechanisms, associations and benefits of nutritional interventions for clinical disease and health promotion.
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