Abstract
BackgroundAlthough high protein diets have been tested in controlled environments for applications to weight management, it is not understood if adding high protein foods to the diet would impact ad libitum energy balance in the absence of other lifestyle changes.MethodsThis double-blinded randomized crossover trial compared the effects of a protein shake (PS) to a carbohydrate shake (CS), consumed prior to each major meal to equate to 20% of total energy needs over the course of the day, on energy balance over two 5-day treatment periods in healthy adults with BMI 20–30 kg/m2. Tri-axial accelerometers estimated physical activity energy expenditure. Ad libitum energy intake was measured in a laboratory kitchen.ResultsEnergy balance was positive during both treatment periods but was not different between periods. There were no interactions between treatment and preload caloric dose or treatment and BMI status on energy balance. Satiety ratings did not differ for any pairwise comparisons between treatment and caloric dose. Controlling for gender and basal metabolic rate, thermic effect of food was greater for PS than CS.ConclusionsPreload periods significantly altered the macronutrient composition of the overall diet. This study found limited evidence that carbohydrate or protein preloads have differential effects on energy balance in short-term ad libitum settings.Trial registrationThis trial was pre-registered on clinicaltrials.gov as NCT02613065 on 11/30/2015.
Highlights
High protein diets have been tested in controlled environments for applications to weight management, it is not understood if adding high protein foods to the diet would impact ad libitum energy balance in the absence of other lifestyle changes
We investigated the effects of prescribed protein intake on ad libitum protein intake and prescribed carbohydrate intake on ad libitum carbohydrate intake to identify if the macronutrient intake was being physiologically regulated
We found little evidence to suggest that preloading egg protein or carbohydrate before each daily major meal, in a dose that corresponds to approximately 20% of energy needs, has differential effects on energy balance over a 5day period
Summary
High protein diets have been tested in controlled environments for applications to weight management, it is not understood if adding high protein foods to the diet would impact ad libitum energy balance in the absence of other lifestyle changes. The protein leverage hypothesis proposes that protein intake is a significant driver of total food intake, such that food low in protein or essential amino acids increases intake, while food in high protein decreases energy intake [8]. This phenomenon has been documented in mice [9]. Practical strategies to meaningfully and consistently alter the macronutrient composition of the diet in ad libitum settings, in the absence of a set menu or highly restricted food access, have not been tested previously, and realistic ways to utilize protein for weight management are currently absent
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