Being big or growing fast: systematic review of size and growth in infancy and later obesity

OBJECTIVES: To assess the association between infant size or growth and subsequent obesity and to determine if any association has been stable over time. DESIGN: Systematic review. DATA SOURCES: Medline, Embase, bibliographies of included studies, contact with first authors of included studies and other experts. INCLUSION CRITERIA: Studies that assessed the relation between infant size or growth during the first two years of life and subsequent obesity. MAIN OUTCOME MEASURE: Obesity at any age after infancy. RESULTS: 24 studies met the inclusion criteria (22 cohort and two case-control studies). Of these, 18 assessed the relation between infant size and subsequent obesity, most showing that infants who were defined as "obese" or who were at the highest end of the distribution for weight or body mass index were at increased risk of obesity. Compared with non-obese infants, in those who had been obese odds ratios or relative risks for subsequent obesity ranged from 1.35 to 9.38. Ten studies assessed the relation of infant growth with subsequent obesity and most showed that infants who grew more rapidly were at increased risk of obesity. Compared with other infants, in infants with rapid growth odds ratios and relative risks of later obesity ranged from 1.17 to 5.70. Associations were consistent for obesity at different ages and for people born over a period from 1927 to 1994. CONCLUSIONS: Infants who are at the highest end of the distribution for weight or body mass index or who grow rapidly during infancy are at increased risk of subsequent obesity.