title: Smaller size of high metabolic rate organs explains lower resting energy expenditure in Asian-Indian Than Chinese men.
abstract: BACKGROUND
  In Singapore, the obesity prevalence is disproportionately higher in the Asian-Indians and Malays than the Chinese. Lower resting energy expenditure (REE) may be a contributory factor.
  
  
  OBJECTIVE
  We explored the association between ethnicity and REE in Chinese, Asian-Indian and Malay men living in Singapore and determined the influence of body composition, mass/volume of high metabolic rate organs, represented by brain volume and trunk fat-free mass (FFM), and physical activity on ethnic differences.
  
  
  METHODS
  Two hundred and forty-four men from Singapore (n=100 Chinese, 70 Asian-Indians and 74 Malays), aged 21-40 years and body mass index of 18.5-30.0 kg m(-2), were recruited in this cross-sectional study. REE was assessed by indirect calorimetry and body composition by dual-energy X-ray absorptiometry. Brain volume was measured by magnetic resonance imaging. Physical activity was assessed by the Singapore Prospective Study Program Physical Activity Questionnaire.
  
  
  RESULTS
  REE was significantly lower in Asian-Indians compared with that in Chinese after adjusting for body weight. FFM (total, trunk and limb) and total fat mass were important predictors of REE across all ethnic groups. Brain volume was positively associated with REE only in Malays. Moderate and vigorous physical activity was positively associated with REE only in Asian-Indians and Malays. The difference in REE between Asian-Indians and Chinese was attenuated but remained statistically significant after adjustment for total FFM (59±20 kcal per day), fat mass (67±20 kcal per day) and brain volume (54±22 kcal per day). The association between REE and ethnicity was no longer statistically significant after total FFM was replaced by trunk FFM (which includes heart, liver, kidney and spleen) but not when it was replaced by limb FFM (skeletal muscle).
  
  
  CONCLUSIONS
  We have demonstrated a lower REE in Asian-Indians compared with Chinese who may contribute to the higher rates of obesity in the former. This difference could be accounted for by differences in metabolically active organs.
authors.affiliation: Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: L L T
authors.initials: LL
authors.lastname: Song
authors.affiliation: Saw Swee Hock School of Public Health, National University of Singapore, Singapore.
authors.forename: K
authors.initials: K
authors.lastname: Venkataraman
authors.affiliation: Singapore Institute for Clinical Sciences, Singapore.
authors.forename: P
authors.initials: P
authors.lastname: Gluckman
authors.affiliation: Department of Obstetrics and Gynaecology, National University of Singapore, Singapore.
authors.forename: Y S
authors.initials: YS
authors.lastname: Chong
authors.affiliation: Center for Cognitive Neuroscience, Neuroscience and Behavioral Disorders Program, Duke-National University of Singapore Graduate Medical School, Singapore.
authors.forename: M-W L
authors.initials: MW
authors.lastname: Chee
authors.affiliation: Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.|Duke-National University of Singapore Graduate Medical School, Singapore.|Division of Endocrinology, National University Health System, Singapore.
authors.forename: C M
authors.initials: CM
authors.lastname: Khoo
authors.affiliation: Office of Clinical Sciences, Duke-National University of Singapore Graduate Medical School, Singapore.
authors.forename: M-Ks
authors.initials: MK
authors.lastname: Leow
authors.affiliation: Singapore Institute for Clinical Sciences, Singapore.|Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.|Division of Paediatric Endocrinology and Diabetes, Khoo Teck Puat-National University Children's Medical Institute, National University Health System, Singapore.
authors.forename: Y S
authors.initials: YS
authors.lastname: Lee
authors.affiliation: Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.|Saw Swee Hock School of Public Health, National University of Singapore, Singapore.|Duke-National University of Singapore Graduate Medical School, Singapore.|Division of Endocrinology, National University Health System, Singapore.
authors.forename: E S
authors.initials: ES
authors.lastname: Tai
authors.affiliation: Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.|Division of Endocrinology, National University Health System, Singapore.
authors.forename: E Y H
authors.initials: EY
authors.lastname: Khoo
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000704:Analysis of Variance; D044466:Asian People; D001481:Basal Metabolism / Q000502:physiology*; D001823:Body Composition / Q000502:physiology*; D015992:Body Mass Index; D001921:Brain / Q000033:anatomy & histology; D003430:Cross-Sectional Studies; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology; D006306:Health Surveys; D006321:Heart / Q000033:anatomy & histology; D006801:Humans; D007668:Kidney / Q000033:anatomy & histology; D008099:Liver / Q000033:anatomy & histology; D008297:Male; D009765:Obesity / Q000208:ethnology* / Q000378:metabolism / Q000517:prevention & control; D009929:Organ Size / Q000502:physiology*; D012146:Rest / Q000502:physiology; D012846:Singapore / Q000453:epidemiology / Q000208:ethnology; D013154:Spleen / Q000033:anatomy & histology; D011795:Surveys and Questionnaires; D044465:White People