Even transient rapid infancy weight gain is associated with higher BMI in young adults and earlier menarche

BACKGROUND: Early postnatal rapid “catch-up” weight gain has been consistently associated with subsequent higher obesity risk and earlier pubertal development. In many low- and middle-income countries, infancy catch-up weight gain is transient and often followed by growth faltering. We explored the hypothesis that even transient catch-up weight gain during infancy is associated with later obesity risk and earlier puberty. METHODS: 2352 (1151 male, 1201 female) black South African children in the Birth to Twenty (Bt20) prospective birth cohort study (Johannesburg-Soweto) underwent serial measurements of body size and composition from birth to age 18 years. At age 18 years, whole-body fat mass and fat-free mass were determined using dual energy x-ray absorptiometry. Pubertal development was assessed by the research team between ages 9 and 10 years, and recorded annually from age 11 years using a validated self-assessment protocol. RESULTS: Catch-up weight gain from birth to age 1 year, despite being followed by growth faltering between ages 1 and 2 years, was associated greater mid-upper arm circumference (p=0.04) and skin fold thickness (p=0.048) at age 8 years, and with higher weight (p<0.001) and BMI (p=0.001) at age 18 years after adjustment for sex, age, smoking during pregnancy, birth order, gestational age, formula-milk feeding and household socio-economic status. Infancy catch-up weight gain was also associated with younger age at menarche in girls (p<0.001). This association persisted after adjustment for smoking during pregnancy, birth order, gestational age, formula-milk feeding and household socio-economic status (p=0.005). CONCLUSION: Transient catch-up weight gain from birth to age 1 year among children born in a low-income area of South Africa was associated with earlier menarche and greater adiposity in early adulthood. This observation suggests that modifiable determinants of rapid infancy weight gain may be targeted in order to prevent later obesity and consequences of earlier puberty in girls.