Milk Proteins' Impact on Protein Synthesis During Hypercaloric, High-Sucrose Diet Explored in Crossover Study

Maintaining lean body mass and regulating energy expenditure are critical factors in preventing long-term body weight gain, especially during periods of caloric surplus. Traditional dietary approaches often struggle to mitigate the adverse metabolic effects of overfeeding, such as increased fat deposition and impaired glucose metabolism. High-protein diets have garnered attention for their potential to enhance satiety and preserve muscle mass, but their specific role in modulating protein synthesis and fat storage during hypercaloric intake, particularly with high sucrose, remains a key research gap. Understanding this mechanism could inform more effective dietary strategies for weight management.

Healthy normal weight male and female subjects will undergo a randomized, crossover study involving two 7-day hypercaloric, high-sucrose diets (+40% excess energy as sucrose). One diet will feature a low protein intake (5% total energy), and the other a high protein intake (20% total energy), with milk proteins as the source. Before and after each 7-day overfeeding period, subjects will undergo a 2-day isoenergetic controlled diet. Primary endpoints include whole-body protein turnover, oxidation, and synthesis measured via 13C-labelled leucine, intrahepatic and intramuscular fat concentration via 1H-Magnetic Resonance Spectroscopy, and energy metabolism via indirect calorimetry. Plasma levels of glucose, insulin, glucagon, GH, IGF1, and IGFBPs will also be assessed.

This abstract describes the study protocol and does not present any findings or results. The primary objective is to compare the effects of high-protein versus low-protein sucrose overfeeding on key metabolic parameters. Specifically, researchers will assess whole-body protein turnover, oxidation, and synthesis in both fasting and fed conditions using 13C-labelled leucine tracers. Changes in intrahepatic and intramuscular fat concentration will be quantified via 1H-Magnetic Resonance Spectroscopy. Energy metabolism will be measured in fasted and fed states using indirect calorimetry. Furthermore, plasma concentrations of glucose, non-esterified fatty acids, total triglyceride, VLDL-triglyceride, insulin, glucagon, growth hormone (GH), insulin-like growth factor 1 (IGF1), and IGF-binding proteins (IGFBP) 1, 2, and 3 will be determined in both fasting and fed conditions. The protocol specifies that whole body protein synthesis will be compared using two-way ANOVA, while linear regression analysis will evaluate relationships between changes in protein synthesis and alterations in fat concentrations, energy expenditure, and plasma metabolic variables.