Acute Thermic Effect of Food in Response to Consumption of Whey Protein Microgels in Overweight Adults

High protein diets have been linked to improved weight loss outcomes and body composition however the role of protein source on energy balance and utilization remains controversial. WPM are aggregates of whey protein (WP) allowing the inclusion of high concentrations of WP in liquid matrices. We investigated the thermic effect of food (TEF) during 330 minutes using indirect calorimetry as well as plasma metabolic markers in response to 4 isocaloric meals: 1) carbohydrate control 2) 30g of WPM (WPM30), 3) 50g of WPM (WPM50) and 4) 50g of micellar casein (MC50), in a crossover trial including 17 overweight subjects. TEF for WPM30 (0.134 ± 0.054), WPM50 (0.180 ± 0.046) and MC50 (0.155 ± 0.045) was significantly greater (p<0.05) than control (0.067 ± 0.037). WPM50 had a higher TEF than WPM30 by 4.6% (p=0.006) which in turn was not significantly different from MC50. No difference was observed between WPM50 and MC50. WPM50 resulted in higher (p<0.0001) plasma levels of leucine, branched chain, essential and total amino acids as compared to MC50 by 93%, 60%, 57% and 28% respectively. Plasma insulin in the WPM50 group was significantly higher (p<0.05) than MC50 by 56%. We conclude that at a dose of 50g, the TEF for WPM and MC is not significantly different in overweight individuals; however WPM results in higher plasma amino acids and a higher insulin response. WPM maintains the advantage over other proteins in delivering a high amount of WP in a small volume to maximally stimulate TEF over control.