Background The protein leverage hypothesis states that human beings will prioritize the consumption of protein in food over other macronutrients and will eat until protein needs have been met (regardless of energy content). This leads to over-consumption of food when protein content is low. The hypothesis has never been tested in obese youth.
Objective To test the protein leverage hypothesis in a cohort of youth with obesity.
Methods Retrospective study in a cohort of youth with obesity attending a tertiary weight management service. Validated food questionnaires (ACAES-FFQ) from 203 individuals were collected, identifyingtotal energy intake (TEI), and percentage energy intake from carbohydrates (%EC), fats (%EF) and proteins (%EP). Individuals with validated measures (Goldberg cut-off >1.2 for reported energy intake/basal metabolic rate from fat free mass) were included for further analysis. Statistics included compositional data analysis (CoDA) to predict TEI from macronutrient-ratios and modelling a power function to estimate the strength of protein leverage (L-coefficient; -1 is complete leverage, 0 no leverage).
Results 137 of 203 participants were included (Goldberg >1.2), mean age 11.3y (SD 2.7), 68 (50%) females, BMI z-score 2.47 (SD 0.27). Mean TEI was 10330 kJ (SD 2728), mean %EC 50.6% (SD 6.1), mean %EF 31.6% (SD 4.9) and mean %EP 18.4 (SD 3.1). The relationship between %EP and TEI followed a power function (Lcoefficient -0.48, p <0.001). Dietary macronutrient content affected total energy intake such that increasing the % of energy from protein was associated with lower total energy intake (p=0.04).
Conclusion This is the first study to show that protein dilution by either carbohydrate or fat is associated with increases in TEI in obese youth. Assessment of dietary protein may therefore be useful in the management of youth with obesity. Further studies are required to show whether manipulation of dietary protein may be beneficial in these patients.