More Protein Combined With Exercise May Lead to Weight Loss and Muscle Gain

Ideally, weight loss involves a loss of body fat and the maintenance or a gain of muscle or lean body mass. This randomized control trial demonstrates that a low-calorie, high-protein diet combined with intense exercise helps promote a loss in fat mass and a gain in lean body mass.

McMaster Researcher

Citation

Phillips S.M., Longland T.M., Oikawa S.Y., Mitchell C.J., & Devries M.C., "Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial," The American Journal of Clinical Nutrition, 103, 3, (2016).  

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What is this research about?

Weight loss regimes that involve a low-calorie diet result in a major loss in fat mass, but can also cause a loss in muscle mass. For athletes in particular, retaining muscle during weight loss is important for optimal physical performance.  The purpose of this study is to explore whether a low-calorie, high-protein diet combined with resistance training and high-intensity training can help promote both weight loss and muscle gain.  

What did the researchers do?

The researchers recruited 40 overweight, but otherwise healthy young men (average age 23 years) who were recreationally active. They randomly assigned 20 participants to the control group, which received a low-calorie, normal-protein diet and the other 20 participants to the intervention group, which received a low-calorie, high-protein diet. Before the study began, the researchers took various measurements from all the participants, including maximal oxygen uptake, strength of knee extensor muscles, peak anaerobic power, bench and leg press strength, weight, body fat, lean body mass, and hormone levels. For the 28-day study, conducted between January 2013 and February 2013, the participants received pre-packed meals based on their assigned diet. All 40 participants also engaged in a six-day per week exercise regime of resistance training and high-intensity training. At the end of the study period, the researchers repeated the same performance and body composition measurements in all of the participants. 

What did the researchers find?

Comparing measurements from the beginning to the end of the study, the researchers found that: 

  • Participants from both groups lost substantial weight  
  • No group lost significantly more weight than the other 
  • Lean body mass remained unchanged in the control group 
  • Lean body mass significantly increased in the intervention group 
  • Fat mass decreased significantly for participants in both groups 
  • This decrease was greater for the intervention group 
  • All exercise performance measurements improved similarly for participants in both groups 
  • Changes in cortisol levels had a small, positive effect on body fat and a small, negative effect on lean body mass 

The study provides evidence that a low-calorie, high-protein diet, combined with resistance training and high-intensity training, can promote fat loss and muscle gain. It also provides evidence that a similar regime, but one with the recommended protein levels, can help maintain lean body mass. 

How can you use this research?

This research is useful to people who want to lose weight and gain muscle. It may also be useful to personal trainers and related professional associations such as the Certified Professional Trainers Network and the Personal Trainer Development Centre.  

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