Relationship between birth weight and body composition, energy metabolism, and sympathetic nervous system activity later in life

OBJECTIVE: Epidemiological studies suggest that high birth weight might be associated with an increased risk of obesity later in life. Programming of metabolic, endocrine, and/or autonomic pathways during intrauterine development has been proposed to explain this association. RESEARCH METHODS AND PROCEDURES: To determine the relationship between birth weight and body composition and energy metabolism later in life, we measured fat mass and fat-free mass (hydrodensitometry or double-energy X-ray absorptiometry), 24-hour energy expenditure, sleeping metabolic rate, and 24-hour respiratory quotient (respiratory chamber) in 272 adult nondiabetic Pima Indians (161 males/ 111 females, age 25 +/- 5 years, mean +/- SD). In these subjects, birth weight varied over a wide range (2,000 to 5,000 g). Individuals known to be offspring of diabetic pregnancies were excluded. In 44 of the 272 subjects, muscle sympathetic nerve activity was assessed by microneurography. RESULTS: Birth weight was positively correlated with adult height (r = 0.20, p < 0.001) and fat-free mass (r = 0.21, p < 0.001), but not with fat mass (r = 0.01, not significant). Sleeping metabolic rate, adjusted for age, sex, fat-free mass, and fat mass, was negatively related to birth weight (r = -0.13, p < 0.05), whereas adjusted 24-hour energy expenditure (r = 0.07, not significant) and 24-hour respiratory quotient (r = -0.09, not significant) were not. There was no relationship between birth weight and muscle sympathetic nerve activity (r = 0.12, not significant, n = 44). DISCUSSION: In Pima Indians who are not offspring of diabetic pregnancies, high birth weight is associated with increased height and lean body mass, but not with increased adiposity later in life. Although high birth weight may be associated with relatively low resting energy expenditure, it is not associated with major abnormalities in 24-hour energy metabolism or with low muscle sympathetic nerve activity later in life.