Testing the Protein Leverage Hypothesis in a Norwegian Population-Based Sample: The Tromsø Study 2015-2016

Abstract

The protein leverage hypothesis proposes that the obesity epidemic is driven by the essential need to obtain sufficient dietary protein. In diets that contain low levels of protein, a leveraging mechanism will cause overconsumption of foods high in carbohydrate and fat as people attempt to reach their protein target. Ultra-processed foods (UPFs) may be involved in this process as they often contain low levels of protein, but high levels of carbohydrates and fat. We investigated these phenomena using cross-sectional data from the large and comprehensive Norwegian population-based study, the Tromsø Study. We examined the relationships between dietary protein intake, total energy intake, body mass index (BMI), and UPFs in a sample from the seventh survey of the Tromsø Study 2015-2016 (n = 11,152; 40–99 years; 53% women). Our analyses revealed that total energy intake decreased as the proportion of dietary protein increased, in line with the protein leverage mechanism. However - and contrary to the protein leverage hypothesis - the relationship between BMI and dietary protein was positive. Our analyses further revealed that as the proportion of UPFs in the diet increased, the proportion of dietary protein decreased, while the total energy intake increased, a finding that supports the protein leverage mechanism. Finally, no clear relationship was established between proportion of UPFs in the diet and BMI. In summary, our study of middle-to older-aged people in a Norwegian population provides strong support for the protein leverage mechanism but no evidence for an effect of protein leverage on BMI.