More than 75 of people with hypertension live in low-to-middle income countries (LMICs). Based on the mismatch theory of developmental origins of disease, we hypothesised that the impact of adiposity on hypertension is augmented in lean compared with not-lean populations in rural areas of LMICs (RLMICs). We reviewed studies from RLMICs in which the association between body mass index (BMI) or waist circumference (WC) and hypertension was assessed using multivariable models. Applying random effect models, we conducted separate meta-analyses, depending on whether BMI/WC was assessed as a continuous or categorical variable. In each analysis, the studies were ranked by the mean BMI of the total population. Those populations with a mean BMI below the median were categorised as lean and those above the median as not-lean. We identified 46 studies of BMI and 12 of WC. The risk of hypertension was greater in lean than in not-lean populations. Obese males in lean populations were 45 more likely to be hypertensive compared to obese males in not-lean populations, ratio of the two effect sizes: 1.45 (95 CI 1.04, 2.03), p = 0.027. Also, individuals with WC above normal in lean populations were 52 more likely to be hypertensive than their counterparts in not-lean populations, ratio of the two effect sizes: 1.52 (95 CI 1.06, 2.17), p = 0.021. We conclude that the risk of hypertension associated with adiposity is greater in lean than in not-lean populations. This provides further evidence for the mismatch theory and highlights the need for strategies to improve nutrition in disadvantaged RLMICs.