Impact of Birth Weight on DXA-Measured Body Composition in Young Adults

Abstract

PURPOSE: Low birth weight has been linked to adult obesity and poor metabolic profiles, as well as abdominal adiposity in later childhood. However, the lasting impact of low birth weight on adult body composition is unclear. Few studies have prospectively examined this relationship into adulthood using criterion measures of body composition. The purpose of this study was to assess whether birth weight influences adult adiposity and fat free mass (FFM). METHODS: We prospectively examined the relationship between birth weight and adult body composition in a cohort of Iowa Bone Development Study participants at age 19. Participants (n=147 females; 116 males) were recruited at birth. Birth weight and gestational age were verified from participant medical records at the time of recruitment. Covariates and body composition measures were collected at age 19. DXA was utilized to measure body composition (kg fat mass (fat); kg FFM; g visceral adipose tissue (VAT)). Gender-specific linear regression was used to assess the association between birth weight (exposure) and adult body composition (outcomes). Models controlled for age, height, fat or FFM, gestational age, and lifestyle factors including Healthy Eating Index and objectively measured moderate-to-vigorous intensity physical activity (MVPA). Fat, VAT, and MVPA were transformed due to non-normal distributions. RESULTS: Participants had an average birth weight of 3.51 kg (range: 0.65 - 5.17). Low birth weight, independent of gestational age, is associated with high VAT (B = −0.070; SE = 0.027; p < 0.01), and low FFM (B = 4.188; SE = 1.174; p < 0.01) in males. In females, low birth weight, independent of gestational age, is associated with high FFM (B = −2.216; SE = 0.728; p < 0.01). CONCLUSIONS: Males born of lower birth weight may have rapid weight gain during the first years of life. This catch-up weight gain may alter the bodies’ ability to store fat, ultimately leading to higher adiposity and lower FFM in adulthood. Results for females suggest other factors may be more influential on body composition, such as genetics or lifestyle factors.