The Impact of a High Protein Diet on Substrate Oxidation and Energy Metabolism
Condition: Dietary Modification
Study type: Interventional

Summary: 
      In the 19th century, researchers found out that the differences in the energy content of
      macronutrients (protein, carbohydrate and fat) can elicit different responses in the amount
      of calories individuals burn per day. It was demonstrated that protein has a metabolic
      advantage when compared to the other macronutrients (carbohydrate and fat). Since these
      findings, researchers all over the world started to study how diets differing in
      macronutrient distribution could result in different responses to energy metabolism. Diets
      with high amounts of protein (i.e. meats, eggs, dairy products, and grains) are becoming more
      popular, and studies have shown that when people eat high quantities of protein they lose
      weight and fat mass, maintain the weight loss, and burn more calories per day.

      The investigators hypothesize that giving high amounts of protein to healthy women will
      increase the amount of calories and fat they burn per day, increase their satiety, and
      improve health markers when compared to a normal diet. The increased protein level will be
      achieved using a nutrition supplement consisted of soy protein, yogurt and honey.

      To test this, the investigators plan to divide the participants in two groups: one will eat a
      normal diet and the other a diet with high amounts of protein during one and a half day.
      After one month they will change groups and eat the other diet for the same period of time.
      During this period consuming the diets (1.5 days), participants will stay inside a whole body
      calorimetry suite, which is similar to a hotel bedroom and is able to inform in the most
      precise way the amount of calories participants will burn and if they are burning more fat.
      Additionally, before and after each meal participants will have to answer a questionnaire
      about their appetite sensations and blood will also be collected to analyze health markers.
    

Detailed description: 
      The aim of this study is to investigate the impact of a high protein diet (achieved through
      the use of a high protein supplement) versus standard diet on substrate oxidation and energy
      expenditure using a state-of-the-art live-in whole body calorimetry unit (WBCU).

      This study will be an acute randomized, controlled, cross-over trial. Healthy women (n=24)
      will receive a run-in diet for three days and will then be randomly allocated into one of the
      following groups: 1) Control group receiving an eucaloric standard diet (55% of carbohydrate,
      15% of protein, and 30% of lipid); 2) High-protein group: eucaloric high protein diet (35% of
      carbohydrate, 40% of protein, and 25% of fat) constructed around a soy protein-based meal
      replacement. The wash-out period will be of approximately one month. While receiving the
      diets in the WBCU for 32 hours, participants' overall change in energy metabolism including
      respiratory quotient will be assessed. Additional assessments include metabolic blood markers
      (glucose, insulin, lipid panel, peptide tyrosine-tyrosine, ghrelin, leptin, free glycerol,
      and free fatty acids), and appetite sensations (hunger and satiety). Body composition and
      energy requirements will be assessed at baseline using dual-energy X-ray absorptiometry and
      indirect calorimetry, respectively.

      It is expected that the high-protein diet will increase lipid oxidation, and energy
      expenditure, with other favorable changes in the additional markers when compared to the
      control group.
    

Intervention name(s): Diet
Intervention type(s): Other
Intervention description(s): The High-Protein Diet Group will receive a eucaloric diet composed of 35% of carbohydrate, 40% of protein, and 25% of lipid constructed around a soy protein-based meal replacement (Almased®) for one and a half day. Participants will consume 1 gram ± 0.1 of Almased® per kg of body weight mixed with linseed oil and skim milk in their breakfast, lunch and dinner. Two snacks (afternoon and evening) composed of 1 gram ± 0.1 of Almased® per kg of body weight mixed with vegetable juice and linseed oil will also be provided.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: High-protein diet; Energy metabolism; Substrate oxidation