The role of dietary protein on muscle mass and resistance exercise

by Rachel Boutagy

Your muscles are the most critical organ for physical and metabolic health, due to their role in supporting all physical movement and being the largest site of glucose disposal after a meal.

The amount of muscle mass you have at any one time, is regulated by muscle protein synthesis (growth) and muscle protein breakdown.

Resistance exercise potentiates pathways that stop or slow down the breakdown of muscle tissue, and when repeated regularly over time, results in muscle hypertrophy.

A recent review from Stuart Phillips group at McMaster University in Canada looked at the role of dietary protein in the promotion of muscle mass with resistance exercise and found the following:

  • If you are performing whole body resistance exercise, you should consume a minimum of 20g of protein every 3-5 hours during the time you are awake to maximise the anabolic effects of protein, but no more than 1.6g - 2.2g per kg of body mass per day. The additional effects of protein are greatly diminished when the daily amount exceed this.
  • If you incorporate periods of energy restriction (such as skipping meals or period of fasting), reduction in muscle tissue is significant, unless followed with resistance exercise, and an increased daily protein intake of 2.3g - 3.1g per kg of lean body mass. If you follow this rule, you can expect gains in lean body mass. By the way, if you are considering using caloric restriction or fasting methods to achieve a goal, be it health or body composition, you should really check out the work of Tony Boutagy, a Phd Exercise Physiologist who really knows his stuff on this topic, not to mention pretty much anything on training and health.
  • The combination of sufficient protein intake and performing regular resistance exercise should form the cornerstone of any weight-loss diet.
  • Athletes who are attempting to cut body mass for a competition several weeks in advance can enhance the satiating effects of each meal, and thus dietary compliance, by ensuring that high quality protein is ingested. During acute periods, whey protein has greater appetite suppressive effects than casein protein, however the situation is reversed when measurements are obtained several hours after food intake. Thus, an athlete may wish to consume a blend of proteins in addition to other whole-food sources to achieve better satiety. However, such a strategy may be unnecessary if protein intakes approach those required to maintain skeletal muscle mass during periods of energy restriction.