Metabolic and Appetite Parameters Following Addition of Whey Protein to a Fat-based Breakfast

Participants will be asked to report to the lab for their first main trial, having not eaten for 12 hours, and refrained from caffeine and alcohol intake and strenuous exercise for 24 hours. Both trials will take place at the same time of day.

Upon arrival height and body mass will be recorded and a cannula will be inserted into a vein in the back of the hand and a 10 ml blood sample will be taken.A visual analogue scale (VAS) will then be used to subjectively measure the participant's appetite pre-breakfast.

Participants will then be provided with one of the two breakfast meals that are being tested in a randomised order. The two breakfasts consist of a high fat breakfast or high fat plus additional whey protein. A drink of water shall also be consumed, the volume of which depends on the trial being carried out. The high fat breakfast will consist of scrambled egg yolks made with single cream and butter (Tesco, Hertfordshire, UK). The macronutrient distribution of the breakfast is 12% protein, 3% carbohydrate, 85% fat (1771 kJ; 423 kcal total). For the whey protein trial, 23.9g whey protein isolate (Lacprodan DI-9224, Arla Foods, Denmark) shall be added to water and incorporated into each meal as a drink on the side, in order to provide 20g whey protein.

A timer shall be set when the participant takes their first mouthful of breakfast, and they will be required to rest for the following 3 hours. At 15, 30, 45, 60, 90, 120, 150 and 180 minutes post-breakfast 10 ml blood samples shall be collected. Every 30 minutes during this period the appetite VAS will also be completed. After this participants will be provided with a standardised lunch meal which shall consist of pasta with a tomato and basil sauce, olive oil and cheddar cheese, along with a 350 ml drink of water. The macronutrient distribution of the lunch is 13% protein, 49% carbohydrate, 38% fat. Following this, the post-breakfast procedure shall be repeated for another period of 3 hours.

Inclusion criteria

• Aged 18-40 years old (male)
• Recreationally active (>30 minutes of structured exercise, 5 times/week)

Exclusion criteria

• Metabolic disease (e.g. Type 2 diabetes, thyroid disorders)
• Taking any prescribed medication
• Regular breakfast skipper
• Food allergies or intolerances
• Eating disorders
• Smoker