Abstract
BackgroundHigh-protein diets and total diet replacements are becoming increasingly popular for weight regulation; however, further research is needed to elucidate their impact on the physiology of body weight regulation. The aim of this inpatient metabolic balance study is to compare the impact of a high-protein total diet replacement versus a control diet (North American) on energy expenditure, macronutrient oxidation rates and balances, metabolic blood markers and appetite sensations in healthy adults.MethodsTwo randomized, controlled, cross-over clinical trials conducted separately in men and women will be conducted. In each trial, participants will be allocated to two isocaloric arms: a) Control diet: 55% carbohydrate, 15% protein, and 30% fat; b) High-protein total diet replacement: 35% of carbohydrate, 40% protein, and 25% fat. They will receive the prescribed diets for 32 h while inside the whole-body calorimetry unit. Diets will be designed to ensure participants are in energy balance. The following physiological changes will be compared between groups: energy expenditure, macronutrient oxidation rates and balances, metabolic blood markers, and appetite sensations. Body composition will be assessed at baseline using dual-energy X-ray absorptiometry.DiscussionThis will be the first inpatient metabolic balance study examining the impact of a high-protein total diet replacement on energy metabolism, metabolic blood markers and appetite sensations in healthy young adults (of both sexes) using a whole-body calorimetry unit. Results of this clinical trial can ultimately be used to develop strategies to optimize high-protein diet interventions and weight management.Trial registrationClinicalTrials.gov Identifiers: NCT02811276 (registered on 16 June 2016) and NCT03565510 (registered on 11 June 2018).Protocol versionNCT02811276: version 10 (2 March 2018); NCT03565510: version 3 (28 September 2018).
Highlights
MethodsTwo randomized, controlled, cross-over clinical trials conducted separately in men and women will be conducted
Defining the ideal macronutrient composition to prevent and treat obesity and its related diseases has been the target of many studies dating back to the 1950s
The energy expended to absorb, process, and store ingested nutrients was determined to be highest for protein (25– 30% of energy content), followed by carbohydrate (6– 8%), and fat (2–3%) [2], suggesting that a diet with a protein content above the recommended values [3] may be advantageous for weight management when compared to other diets with different proportions of macronutrients [4]
Summary
Study design and ethical procedures These studies will be randomized, controlled, crossoverdesigned, clinical trials conducted separately in women and men at the Human Nutrition Research Unit (HNRU), University of Alberta (Edmonton, AB, Canada). Eligible participants will be invited to attend two study visits for a body composition assessment, a 1-h RMR test, and a fitness test After these visits are complete, on separate intervention days, participants will undergo two 32-h wholebody calorimetry stays for the measurement of energy metabolism components, appetite sensations, and metabolic blood markers while consuming HPTDR and CON isocaloric diets in a random order. Blood and urine analysis Blood will be sampled by venipuncture from participants at four time points during each whole-body calorimetry condition: 1) the morning on the first day of the test (Baseline); 2) immediately after the exercise session (4 h post-baseline); 3) two hours after lunch (7.5 h post-baseline); and 4) the morning on the second day of test (24 h post-baseline) Both morning blood draws will be sampled from subjects after a 10-h overnight fast. The protocol versions are 1) NCT02811276: version 10 (2 March 2018) and 2) NCT03565510: version 3 (28 September 2018)
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