Using the Protein Leverage Hypothesis to Understand Socioeconomic Variation in Diet and Obesity
Background: The rising prevalence of obesity among the urban poor in Latin America is unexplained due to limited data on dietary intake and physical activity in this population. The Protein Leverage Hypothesis (PLH) predicts that when the proportion of protein in the diet is low, protein appetite will stimulate excess energy intake, and consequently obesity.
Objective: Guided by the PLH, this study evaluated an explanation for the inverse relationship between SES and obesity: limited access to dietary protein among low-SES women leads them to consume a lower proportion of protein in the diet which, in turn, drives higher energy intake and hence obesity.
Methods: This was a cross-sectional study conducted in a random sample of 140 low-, middle- and high-SES women in urban Costa Rica. SES was defined based on individual, household and neighborhood characteristics. Anthropometry was used to calculate Body Mass Index (BMI). Twenty-four-hour dietary recalls were used to measure dietary intake. Structured interviews were used to examine women’s perceptions of the desirability and cost of different sources of dietary protein. A Global Positioning System (GPS) and Google Maps were used to measure the distance women travel to access different sources of dietary protein.
Results The prevalence of obesity varied between low- (39.2%), middle- (42.9%) and high- (17.8%) SES women (p=0.02). The proportion of protein in the diet varied between low- (13.1%), middle- (13.7%) and high- (16.1%) SES women (p
Conclusion: Approaches to understanding the dietary causes of obesity that focus solely on the role of carbohydrates and fats may be overlooking the importance of dietary protein. Protein leverage should be studied further outside of laboratory settings in the context of real world conditions that may contribute to obesity.