A randomized cross-over trial to determine the effect of a protein vs. carbohydrate preload on energy balance in ad libitum settings

Abstract

Background: Although 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.

Methods: This 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.

Results: Energy 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.

Conclusions: Preload 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 registration: This trial was pre-registered on clinicaltrials.gov as NCT02613065 on 11/30/2015.

Keywords: Cross-over trial; Egg; Energy balance; Macronutrients; Preload; Protein; Randomized trial.

Conflict of interest statement

The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. Indiana University has received funds or pledges for funds from the Egg Nutrition Center for scientific and education activities. DBA discloses the following potential conflicts of interest: Ikea, The Law Offices of Ronald Marron, Nestle Research Center, Biofortis, Fish & Richardson PC, and Tomasik, Kotin & Kasserman. JAD has received funding from the American Egg Board. MJG has received travel expenses from TriNetX.

Figures

Fig. 1

Study design from randomization through intervention completion. CS, carbohydrate shake; PS, protein shake; TEF, thermic effect of food

Fig. 2

CONSORT flow diagram from enrollment through analysis. CS, carbohydrate shake; GID, Gastrointestinal discomfort; PS, protein shake; TEF, thermic effect of food

Fig. 3

VAS satiety ratings reported by subjects immediately after shake consumption (0 min) and 15, 90, 180 min after buffet lunch completion on day 1 and day 5 of both treatment periods. NW-CS, participants with normal weight on carbohydrate shake (n = 11); NW-PS, participants with normal weight on protein shake (n = 9); OW-CS, participants with overweight on carbohydrate shake (n = 12); OW-PS, participants with overweight on carbohydrate shake (n = 12); Desire, self-reported VAS for “How strong is your desire to eat now?”; Full, self-reported VAS for “How full do you feel now?; Hungry, self-reported VAS for “How hungry do you feel now?”; Appetite, self-reported VAS for “How much food do you think you could eat now?”; VAS, Visual Analog Scale

Fig. 4

Energy expenditure due to thermogenesis of preload shakes, adjusted for baseline BMR and gender (n = 48). EE, energy expenditure; Female-CS, females on carbohydrate shake; Female-PS, females on protein shake; Male-CS, males on carbohydrate shake; Male-PS, males on protein shake; RMR, resting metabolic rate; TEF, thermic effect of food

Fig. 5

Percent contribution of macronutrients to total daily caloric intake according to treatment period (n = 43). PS, Protein shake; CS, Carbohydrate shake. *p value < 0.05