title: Variation in the heritability of body mass index based on diverse twin studies: a systematic review.
abstract: OBJECTIVE
  Over the past three decades, twin studies have shown variation in the heritability of obesity. This study examined the difference of body mass index (BMI) heritability (BMI-H) by population characteristics, such as sex, age, time period of observation and average BMI, as well as by broad social-environmental factors as indicated by country-level gross domestic product (GDP) per capita and GDP growth rate.
  
  
  METHODS
  Twin studies that reported BMI-H and were published in English from January 1990 to February 2011 after excluding those with disease, special occupations or combined heritability estimates for country/ethnic groups were searched in PubMed. 32 studies were identified from Finland (7), the United Kingdom (6), the United States (3), Denmark (3), China (3), Netherlands (2), South Korea (2), Sweden (2) and four from other countries. Meta-regression models with random effects were used to assess variation in BMI-H.
  
  
  RESULTS
  Heterogeneity of BMI-H is significantly attributable to variations in age (<20, 20-55 and ≥56 years), time period of observation (i.e. year of data collection), average BMI and GDP (≤$20,000, $20,001-26,000 and >$26,000). BMI-H was higher in adolescents (<20 years), in studies done in past years, and in populations with higher average BMIs or higher GDP per capita (≥$26,000) than their counterparts. Consistent lowering effects of high GDP growth rate (>median) on BMI-H were shown through stratified analyses by GDP. BMI-H was lower in countries of mid-level GDP, particularly those experiencing rapid economic growth.
  
  
  CONCLUSIONS
  BMI-H is sensitive to age, time period of observation, average BMI, GDP and rapid economic growth.
authors: Johns Hopkins Global Center on Childhood Obesity, Department of International Health Human Nutrition Program, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA; Department of Preventive Medicine, School of Medicine, Ewha Womans University, Seoul, Korea.
authors: J
authors: J
authors: Min
authors: D T
authors: DT
authors: Chiu
authors: Y
authors: Y
authors: Wang
mesh_terms: D000367:Age Factors; D015992:Body Mass Index; D006801:Humans; D009765:Obesity / Q000191:economics / Q000235:genetics*; D019655:Quantitative Trait, Heritable; D012044:Regression Analysis; D012737:Sex Factors; D012959:Socioeconomic Factors; D018433:Twin Studies as Topic / Q000191:economics
keywords: Body mass index; GDP; heritability; twin study
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