Influence of birth size on body composition in early adulthood: the programming factors for growth and metabolism (PROGRAM)-study.

BACKGROUND/
OBJECTIVES: Several studies have investigated the relationship of birth size with fat mass and lean body mass (LBM), but the findings differed greatly due to different ways of measuring FM and LBM, different study populations and age groups. We hypothesized that birth size has no influence on adult body composition, whereas weight gain during childhood has.
METHODS: In the programming factors for growth and metabolism (PROGRAM)-study, a cohort of 312 young adults, aged 18-24 years, FM and LBM were determined by dual energy X-ray absorptiometry (DXA). Subsequently, differences in FM and LBM were analysed in four subgroups, young adults either born small for gestational age with short stature (SGA-S) or with catch-up growth (SGA-CU), or born appropriate for gestational age (AGA) with idiopathic short stature (ISS) or with normal stature (controls).
RESULTS: Age, gender, adult height SDS and adult weight SDS were significant positive determinants of FM and LBM, whereas weight gain during childhood was positively significant for FM and negatively for LBM. Birth weight SDS tended to be significant and birth length SDS was not. Weight gain during childhood was positively correlated with waist : hip ratio and trunk fat : total fat ratio. SGA-CU subjects had significantly higher FM and significantly lower LBM than controls.
CONCLUSION: Weight gain during childhood is an important determinant of body composition in young adulthood, whereas birth size is less important. In clinical practice, too much weight gain in childhood should be prevented as it results in a relatively high fat mass, especially in children with catch-up growth in weight, like SGA-CU subjects.