Age-dependent nongenetic influences of birth weight and adult body fat on insulin sensitivity in twins.

Objective: We hypothesized a nongenetic influence of birth weight (BW) and twin and zygosity status on dual-energy x-ray absorptiometry determined adult total and regional body composition and a quantitative equal, although independent, importance of adult body composition and BW for insulin sensitivity.

Design And Methods: This was a clinical study of 110 young (aged 22-31 yr) and 86 elderly twins (aged 57-66 yr) and 32 age-matched controls with measures of BW, adult body composition, and insulin sensitivity.

Results: BW was nongenetically, positively associated with height, weight, and total and regional (trunk, arm, and leg) fat mass and percentages in the young twins.

Total and regional fat distribution is strongly influenced by genetic factors in young and elderly twins.

Objective: Indirect estimates of obesity such as BMI seem to be strongly influenced by genetic factors in twins. Precise measurements of total and regional fat as determined by direct techniques such as DXA scan have only been applied in a few twin studies. The aim of the present study was to estimate the heritability (h(2)) of total and regional fat distribution in young and elderly Danish twins.