<b><i>Background:</i></b> Exposures during early life are increasingly being recognised as factors that play an important role in the aetiology of chronic non-communicable diseases (NCDs). The “Developmental Origins of Health and Disease” (DOHaD) hypothesis asserts that adverse early-life exposures - most notably unbalanced nutrition - leads to an increased risk for a range of NCDs and that disease risk is highest when there is a “mismatch” between the early- and later-life environments. Thus, the DOHaD hypothesis would predict highest risk in settings undergoing a rapid nutrition transition. <b><i>Summary:</i></b> We investigated the link between early-life nutritional exposures and long-term health in rural Gambia, West Africa. Using demographic data dating back to the 1940s, the follow-up of randomised controlled trials of nutritional supplementation in pregnancy, and the “experiment of nature” that seasonality in this region provides, we investigated the DOHaD hypothesis in a population with high rates of maternal and infant under-nutrition, a high burden from infectious disease, and an emerging risk of NCDs. <b><i>Key Messages:</i></b> Our work in rural Gambia suggests that in populations with high rates of under-nutrition in early life, the immune system may be sensitive to nutritional deficiencies early in life, resulting in a greater susceptibility to infection-related morbidity and mortality.