Metabolic and Appetite Responses to Altered Timing of Whey Protein Ingestion

Overview

The proposed study aims to determine the metabolic and appetite responses to standard breakfast and lunch meals whilst altering the timing of whey protein supplementation. Currently, the designs implemented in many studies mean that it is unclear whether an optimum time for whey protein consumption exists in order to promote the greatest acute health benefits. A number of studies have investigated the effects of whey protein when consumed as a preload to a subsequent meal, whilst benefits have also been shown when whey protein is ingested with a meal. The proposed study will therefore investigate strategies of whey protein supplementation that vary in their practical applicability, using meals that reflect regular eating behaviours throughout the population in a sample of overweight/obese individuals. Findings from this study may provide important information regarding the efficacy of whey protein supplementation before, during and after a composite meal, and its effect on the handling of a subsequent mixed-macronutrient meal.

A randomised crossover design shall be implemented, whereby all participants complete 4 trials separated by a minimum of 3 days. On all visits participants shall consume a standardised mixed-macronutrient breakfast meal, followed 180 minutes later by consumption of a standard lunch meal. The timing of additional protein supplementation shall vary by trial, with participants consuming a shake containing 20g whey protein isolate either as a preload (15 minutes prior to breakfast), alongside the breakfast meal, or 15 minutes following breakfast consumption. A control trial shall also be completed without additional protein supplementation. At all supplementation time points participants shall consume either a flavoured whey protein shake or a flavoured water isovolumetric beverage ensuring that they remain blinded to the condition. Venous and capillary blood samples and visual analogue scales (for determination of subjective appetite sensations) shall be taken at regular intervals following both meals while the participant is rested.