None listed
Conditions
Brief summary
Protein intake has remained relatively stable through the development of the obesity epidemic. The protein leverage hypothesis proposes that a separate and dominant appetite for protein drives excess energy intake when dietary protein is diluted by fat and carbohydrate. We have provided convincing evidence that when the percent protein of the diet is reduced from 25% to 10% by increasing percent carbohydrate and keeping fat constant at 30% lean humans respond by increasing total energy intake. Recent data from a rodent dietary model suggests that intake of protein and carbohydrate is regulated (with protein dominating) but intake of fat is not. If dietary fat is not regulated in humans we would predict that the protein leverage effect will be even stronger if protein and fat co-vary in experimental diets and carbohydrate is kept constant at an adequate level. The aim of the study is to test whether converse changes in fat rather than carbohydrate will accentuate the protein leverage effect in covert trials. To do this we will manipulate the protein to energy ratio of the diet by increasing or decreasing the protein content whilst respectively decreasing or increasing the carbohydrate or fat content on 4 occasions for 4-days.
Interventions
Each participant attended four, 4-day periods of in-house dietary manipulation. Participants will be given ad libitum access to diets containing varying protein content (10% and 25%), and the nutrient used to adjust dietary protein concentrations (carbohydrate or fat). The 4 diet treatments will be matched for palatability and energy density. The 4 diet composition will be as follows:
Fixed fat, variable carbohydrate
Diet 1: 10% protein, 30% fat and 60% carbohydrate
Diet 2: 25% protein, 30
Each participant attended four, 4-day periods of in-house dietary manipulation. Participants will be given ad libitum access to diets containing varying protein content (10% and 25%), and the nutrient used to adjust dietary protein concentrations (carbohydrate or fat). The 4 diet treatments will be matched for palatability and energy density. The 4 diet composition will be as follows: Fixed fat, variable carbohydrate Diet 1: 10% protein, 30% fat and 60% carbohydrate Diet 2: 25% protein, 30% fat, 45% carbohydrate Fixed carbohydrate and variable fat Diet 3: 10% protein, 40% fat and 50% carbohydrate Diet 4: 25% protein, 25% fat and 50% carbohydrate Participants will be given ad libitum access to study food with no access to other foods during each intervention period. Participants will have free access to a variety of foods all day and can initiate their own meal times. Participants will be asked to leave any uneaten foods and/or empty packages in a designated bag. Food intake will be measured by recording the weight of food before and after serving, to the nearest gram. Energy intake will be calculated using the nutritional information for each recipe. The trial will be a randomised cross-over trial, each participant completed each of the four 4-day interventions with at least a one week washout period between interventions.
Sponsors
The University of Sydney
Study design
Allocation
Randomised controlled trial
Intervention model
Crossover
Primary purpose
Prevention
Masking
Blinded (masking used) (Subject)
Eligibility
Sex/Gender
All
Age
18 Years to 65 Years
Healthy volunteers
Yes
Inclusion criteria
Lean (BMI < 25 kg/m2), healthy male and female participants
Exclusion criteria
Pregnancy or planning pregnancy, breastfeeding, known diabetes, known unstable or untreated elevated blood pressure or cholesterol, cardiovascular disease, chronic inflammatory conditions, medications that interfere with glucose metabolism, smoking, alcohol consumption above current NHMRC dietary guidelines, allergy or intolerance to any of the intervention foods, irregular eating patterns or eating disorder, following a weight reducing diet. Vegetarians and Vegans will be excluded to aid preparation of covertly manipulated foods.
Outcome results
None listed