Associations of size at birth and dual-energy X-ray absorptiometry measures of lean and fat mass at 9 to 10 y of age.

BACKGROUND

Birth weight has been positively associated with risk of overweight in later life. However, little information exists on how weight and length at birth are associated with subsequent lean and total body fat.

OBJECTIVE

We investigated the association between weight and length at birth and body composition and fat distribution in childhood.

DESIGN

Body composition was measured by using dual-energy X-ray absorptiometry in 9-10-y-old subjects (n = 3006 boys and 3080 girls). Weight and length at birth were measured or taken from hospital records.

RESULTS

Birth weight was positively associated with both lean body mass (LBM) and total body fat at 9-10 y of age in both sexes. LBM rose by 320 g per 1-SD increase in birth weight (P < 0.001), and total body fat rose by 2.5% (P = 0.001), but birth weight was unassociated with the fat-to-lean mass ratio (FLR). Ponderal index (PI) at birth (ie, weight/length3) was positively associated with LBM, total body fat, and the FLR in both sexes; the FLR increased by 2.7% in boys (P = 0.021) and by 5.0% in girls per 1-SD increase in PI (P < 0.001). Weight and length at birth did not predict central adiposity; although trunk fat had a strong positive association with PI at birth, this association disappeared after adjustment for total body fat.

CONCLUSIONS

Higher PI at birth is associated with both higher fat and lean mass in childhood but also with an increase in the FLR. PI at birth is a better predictor of subsequent adiposity than is birth weight.