Whey Protein Study - Identification of Sustainable Satiety
Condition: Satiety
Study type: Interventional

Summary: 
      This study will have the primary aim to investigate within-day changes in appetite after
      consumption of high-protein (HP, 30% of calories) and normal, or low, protein (LP, 15% of
      calories) whey protein meal, in solid and liquid form, on appetite and ad libitum food
      intake. Secondary objective will be to assess the statistical relationship between plasma
      concentrations of gut hormones and visual analogue scales (subjective hunger and fullness)
      and transit time.

      In order to investigate the interaction of food structure and protein content on appetite,
      this requires, in practice, either a differing amount (g) or calorie (kJ) load as a function
      of energy density (defined as kJ/100g). Delivering the test meal as a solid and liquid form
      gives an easy solution to achieve this manipulation without compromising the nutritional
      profile. Following on from this decision, it is easier to produce different preloads using
      whey protein (rather than meat protein), since it is easily incorporated into test meals.
    

Detailed description: 
      A randomized crossover design in 10 overweight/obese (BMI 26-40) men and 10 lean men (BMI
      18.5-25). The control will be water. Each subject will attend the HNU on six separate
      occasions. The five test meal challenges will involve subjects attending the Human Nutrition
      Unit (HNU) in the morning, after an overnight fast. The total time of test meal visits will
      be approximately 4½hours. They will be provided with a standardised meal, after which blood
      samples will be collected for the first 2hrs. The following five treatments will be tested:

      Treatment 1 Control - Water + Egg Yolk Mixture + 13C Octanoic Acid Treatment 2 HPL (High
      Protein Liquid): 30% protein; 30% fat and 40% carbohydrate (CHO) Treatment 3 LPL (Low Protein
      Liquid): 15% protein; 30% fat and 55% CHO Treatment 4 HPS (High Protein Solid): 30% protein;
      30% fat and 40% CHO Treatment 5 LPS (Low Protein Solid): 15% protein; 30% fat and 55% CHO
      Test meals will be of fixed nutritional composition for all participants. The liquid meal
      will be a milk/fruit smoothie mixture and the 'solid' will be in a milk jelly (set) form.

      Ad libitum pasta meal: 15% protein; 30% fat and 55% CHO as a homogenous mix and energy
      density of around 400kJ/100g - served in excess as a individual 600g portion to
      'help-yourself'.

      Subjective average appetite will be measured (every 30 min by visual analogue scales) over
      4hr and ad libitum food intake will measured 4hr after treatment consumption. Ad libitum
      lunch will be a homogenous pasta meal with tomato sauce and a bottle of water. Blood samples
      will be collected every 10 min for the first half hour, every 15 min for the second half hour
      and every 30mins subsequently. The breath gastric emptying measurement will be assessed using
      the 13Carbon (13C) Octanoic Acid stable isotopic technique19. This involves mixing the tracer
      into food and taking breath samples and measured by isotope ratio mass spectrometry. 13C
      Octanoic acid is a medium chain fatty acid which is rapidly absorbed in the duodenum and
      metabolised in the liver. Following oxidation, the resulting Carbon Dioxide (CO2) is excreted
      into breath (12 samples will be collected during the 4hr test day).
    

Intervention name(s): Control; HPL; LPL; HPS; LPS
Intervention type(s): Dietary Supplement; Dietary Supplement; Dietary Supplement; Dietary Supplement; Dietary Supplement
Intervention description(s): Water, Toast & Egg (Yolk only) + 0.1g 13C Octanoic Acid; High Protein Smoothie (Liquid): 30% protein; 30% fat and 40% CHO + 0.1g 13C Octanoic Acid; Low Protein Smoothie (Liquid): 15% protein; 30% fat and 55% CHO + 0.1g 13C Octanoic Acid; High Protein Milk Jelly (Solid): 30% protein; 30% fat and 40% CHO + 0.1g 13C Octanoic Acid; Low Protein Milk Jelly (Solid): 15% protein; 30% fat and 55% CHO + 0.1g 13C Octanoic Acid
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Single (Participant)
Primary purpose: Basic Science
Keywords: Appetite; Gut Hormones; Protein; Energy Density; Gastric Emptying