Exercise and Nutrition Research Program

The effect of intermittent fasting on integrated muscle protein synthesis rates in overweight, middle-aged men

A sustained energy deficit, achieved through a reduction in energy intake and/or increased energy expenditure, is a prerequisite for the loss of body mass and treatment of obesity. Dietary energy restriction (ER) is commonly used to reduce total body mass; however, a potentially unfavorable consequence of ER is the loss of lean body mass (LBM). Given that skeletal muscle is the largest component in LBM and a highly metabolically active tissue, such loss could have an important impact on mobility and aspects of metabolic health. Moreover, the age-related loss of muscle mass (termed sarcopenia) is exacerbated in overweight and obese individuals. Therefore, the critical health issue for a large proportion of adults in developed nations is how to lose fat mass while preserving muscle mass. Thus, strategies that promote the preservation of LBM during ER are of clinical importance.

Intermittent fasting is a dietary strategy involving abstaining from eating for periods longer than the typical overnight fast. Intermittent fasting diets have been shown to effectively reduce body weight, fat mass, lower skeletal muscle insulin resistance, and improve overall metabolic health. Popular regimens in intermittent fasting protocols include alternate day fasting (ADF) and time restricted eating (TRE). Alternate day fasting involves alternating ad libitum eating days with fasting days, which typically consist of 1 meal consumed that contains ~25% of the baseline energy needs for the individual. TRE is a dietary strategy during which the daily period of food intake is limited to 8 h or less, and as such, prolonging the overall period of fasting during 24 h without reducing total energy intake.

Several short-term human clinical trials have shown that intermittent fasting protocols such as ADF and TRE can deliver benefits similar to continuous ER in terms of weight loss and metabolic health, including a reduction in body weight and fat mass, improved lipid profiles, lower blood pressure, and increased insulin sensitivity. Therefore, dietary interventions that are accompanied by long fasting periods have emerged as promising strategies to target several clinical parameters that constitute the foundation for metabolic syndrome, cardiovascular disease, cancer, and even neurodegenerative diseases. However, the specific mechanisms are far from being fully understood and the impact of IF on muscle mass maintenance remains unknown.

The present study aims to assess the effect of short-term (10 day) alternate day fasting, time restricted eating, or continuous energy restriction with matched optimal protein intakes when compared with a control diet on integrated skeletal muscle protein synthesis rates in overweight, middle-aged males. This study is currently recruiting participants and is expected to be completed by June 2020.

Funding

Dr Imre Kouw received an Early Career Research Fellowship from the European Society of Clinical Nutrition and Metabolism (ESPEN) and Early Career Research Grant from the Faculty of Health Sciences, ACU for this study.

Duration

June 2018- June 2020

Investigators

Dr Imre Kouw

Dr Evelyn Parr

Professor John Hawley

Professor Luc van Loon, Maastricht University and ACU

Ms Bridget Radford

Ms Rebecca Hall

Mr Michael Wheeler