The Effect of Beverages Varying in Protein Quantity on Appetite and Energy Intake

The Acute Effect of Beverages Varying in Macro-nutrient Content on Subjective Appetite Ratings and ad Libitum Energy Intake in Healthy Subjects

Over the last decades, changes in the diet and lifestyle have led to overall energy imbalance becoming commonplace and the emergence of an obesity epidemic with more than 1.6 billion adults being overweight.

Consumption of foods that can affect appetite by increasing satiety could regulate the total energy intake and thus body weight. There is data suggesting that the macronutrient composition of the foods and especially protein content may have a potent role on satiety. However, it is difficult to pinpoint the optimum quantity needed to observe significant effects of protein on satiety.

The research project is dedicated to identify which food components [proteins, carbohydrates (CHO), fats] and the optimized protein quantity needed to accelerate satiation, suppress appetite and extend satiety until hunger appears again.

It is hypothesized that the consumption of protein-enriched meals will induce a reduction in hunger through the impact on gut hormones and peptides that are closely related to the short-term regulation of food intake.

Inclusion Criteria:

• Healthy males and females
• Age range 18-50 years
• Normal weight and overweight people as classified by BMI:22-27.9 kg/m2 (inclusive).
• Weight stable (within 3 kg) two months prior to study inclusion
• Understanding English well and feeling comfortable speaking it

Exclusion Criteria:

• Dietary protein consumption >25% energy from protein
• Had surgery in the previous 12 months
• Have suffered a myocardial infarction or stroke at any time
• Suffer from any blood-clotting disorder or prescription of any medication affecting blood clotting
• Suffer from any metabolic disorders (e.g. diabetes, metabolic syndrome or hypertension)
• Any requirement to take long-term medication, especially those active on the gastro-intestinal tract or for cardio-vascular disease
• Any dietary restrictions or recently/currently on a weight reducing diet
• Irregular eating patterns or not regularly consuming breakfast
• Food allergies (e.g. milk protein allergies) or intolerances (e.g. lactose)
• Use of medication which affects food intake or behaviour (e.g. anti-depressants)
• Use of medication likely to affect taste, smell or appetite
• Eating restraint based on the three Factor Eating Questionnaire
• Use of any protein supplements
• A history of alcohol or drug misuse (the average daily number of units of alcohol considered as acceptable is 2-3 units women; 3-4 units men
• Smoking
• Athletes in training (>10 h exercise/week)
• Female that is breast-feeding, pregnant, or if of child-bearing potential and are not using effective contraceptive precautions
• Involvement in a study involving an experimental drug/medication within 3 months prior to entry of this study
• Blood pressure > 160/90 mmHg
• Vegan or Vegetarian
• Glucose > 6 mmol/L
• Gamma glutamyl transferase > 1.9 μkat / L
• Alanine transaminase > 1.1 μkat / L
• Cholesterol > 6.5 mmol/L
• Triglycerides > 2.0 mmol/L