Metabolic and Appetite Responses to a Whey Protein Preload Following Prior Exercise in Overweight Males

Overview

Consuming whey protein may have beneficial effects on health, principally by having an impact on blood glucose metabolism, but also by affecting appetite. The purpose of this project is to investigate the effect of consuming whey protein preload prior to breakfast, following a bout of low/moderate intensity exercise (brisk walking), on glucose and lipids in the blood as well as on appetite. It is hypothesised that the consumption of whey protein before a meal after prior low/moderate intensity exercise may positively affect postprandial handling as well as appetite sensations and consequently reduce intake at a subsequent meal.

A crossover design shall be implemented, whereby all participants complete 3 experimental trials in random order, separated by a minimum of 5 days. Participants will be asked to record their dietary intake for 24 hours before each trial and will be provided with a standardised meal to consume at a set time the previous evening. At each visit participants shall report to the lab at approximately 08.00 hours following a 12 hour fast and having refrained from caffeine, alcohol and vigorous physical activity for 24 hours. After determination of body mass and stature, a cannula shall be inserted into an antecubital vein in order to collect venous blood samples. A baseline blood sample (10ml) shall be collected, and visual analogue scales (VAS) completed in order to assess appetite sensations. Following this a 30 minute exercise bout shall be completed in two of the trials, with 30 minutes of seated rest carried out in the control trial. Participants shall walk on a motorised treadmill at a predetermined speed designed to reflect 55% of estimated maximal aerobic capacity. Heart rate and perceived exertion will be sampled every three minutes, while expired air shall be sampled for two minute periods at 5, 15 and 25 minutes. During the preload trial, participants shall consume a whey protein beverage 15 minutes after completion of the exercise bout. This will consist of 23g whey protein isolate powder (20g protein) combined with 200ml water and 10 drops of energy-free flavouring to create a milkshake-type beverage. In both other trials an isovolumetric bolus of similarly flavoured water shall be consumed. After a further 15 minutes participants shall consume the same mixed-macronutrient breakfast meal under all conditions, and will subsequently rest for a 240 minute period. An ad libitum pasta meal shall be consumed at the end of this period in all trials in order to assess subsequent energy intake. Regular blood samples shall be collected throughout.