Obesity is emerging as early as two years of age and risk may be elucidated by differences in infant growth trajectories. We examined infant weight gain in the first year of life and association with overweight/obesity at age two.

In a diverse, population-based cohort study we conducted growth curve analysis using Health Maintenance Organization electronic medical record data from January 1, 2012 through December 31, 2013.

Among 930 infants, there was a linear relationship with birth weight and initial weight gain from birth and increased odds of developing overweight/obesity at age two [Odds Ratio OR = 1.001; (95% CI: 1.000–1.002), p = 0.0274] and [OR = 1.009; (1.006–1.01), p = 0.0001) respectively. The odds of becoming overweight/obese at age 2 increased in infants who had slower weight deceleration rates (OR third quartile = 2.78, fourth quartile = 4.3) compared to the first quartile. Other factors associated with overweight/obesity risk at age two included female sex and Native Hawaiian race/ethnicity.

Rate of weight gain in the first year may be an important risk factor for early childhood obesity. A deeper dive into first year growth patterns and related sociocultural and nutritional factors is needed to inform targetable points for intervention.