Due to the high prevalence of obesity and lack of treatments that produce long-term weight loss, it is critical to better understand the process of weight gain, and the patterns in the development of obesity over time, in addition to the overall trajectory and outcome. Weight variability, or how much body weight varies over time independent of total weight loss or gains, might be predictive of later weight and health risk outcomes. Weight variability in adults has been associated with weight gain over a period of 18 months (Lowe et al 2015), and variability in week-to-week weight change in a weight loss program was associated with poorer long-term weight loss (Feig & Lowe submitted). In addition, research has suggested that weight variability is associated with adverse health problems including cardiovascular risk factors, heart disease, and stroke (Lissner 1991; French 1997). It is important to understand individual differences in weight variability because it may predate an increase in weight and ultimately the development of overweight or obesity, or the development of health risk factors. One explanation is that elevated weight variability is a marker of a breakdown of the body weight regulatory system that is weakened by biological or environmental factors. Therefore identifying these predictors of susceptibility to weight gain and health risks prior to the onset of health and weight problems could be useful in disease prevention. Little is known about weight variability in young children or infants. In this study we will look at weight variability in infancy and childhood as a predictor of later weight gain, as well as other physiological variables reflective of medical risk (e.g. blood pressure). Understanding the markers of weight gain and health risk will help develop targeted treatment methods, even prior to onset of disease.