Using a restrictive diet for weight loss, unless done properly, can result in not only the loss of fat mass, but also skeletal muscle. Achieving as low as possible ratio of skeletal muscle to fat mass loss is called 'High Quality Weight Loss' and is important for maintaining one's engine (muscle) and improving athletic performance.
Current recommendations for protein intakes during weight loss are set at 1.6–2.4 g protein/kg/day, however, the severity of the caloric deficit and type and intensity of training performed will influence at what end of this range you choose to be.
A recent review from Stuart Philips group at McMaster University discussed the use of protein supplementation to achieve high quality weight loss. They found that whey protein either as a supplement or incorporated into a weight loss or weight maintenance diet, promotes lean body mass retention and fat mass loss, positively effects strength, muscle fibre cross-sectional area and bone mass during prolonged resistance training and may have a positive effect on high-quality weight loss for elite athletes during dietary energy restriction.
BCAA's have also been of interest for promoting skeletal muscle gains and high-quality weight loss. However a common concern with BCAA supplementation is the antagonism of amino acids leucine, isoleucine, and valine in competing for the BCAA transporter. Isoleucine and valine have been shown to inhibit the absorption of leucine, a potent stimulator of muscle protein synthesis. Based on the current data, BCAA supplementation, does not appear to have strong scientific evidence for it's utility in supporting high-quality weight loss, and may even have negative side effects. It therefore seems equivocal to consume BCAA supplements during dietary energy restriction, when one can simply consume a complete protein supplement such as whey protein, which has been shown to promote a robust increase in muscle protein synthesis during dietary energy restriction.
The review also discussed other important considerations in high-quality weight loss during energy restriction, including the quality of protein consumed, and the timing and distribution of protein intake throughout the day. Here is what they found.
- A more balanced pattern of 4 x 20g doses of protein every 3 hrs during the day has been shown in a number of studies to increase muscle protein synthesis, lean mass and strength in both trained and elderly populations during energy restriction.
- Sleep is critical for recovery and performance and represents a prolonged postabsorptive period where muscle protein balance is negative and could be improved. Indeed, presleep protein supplementation combined with exercise training has been shown to improve protein balance during the prolonged postabsorptive overnight period. Thus, presleep protein ingestion may be another strategy to improve lean body mass retention during caloric restriction.
- Protein quality also plays a role in maximising lean body mass during caloric restriction. High quality proteins contain a higher proportion of essential amino acids, which are known to be potent stimulators of muscle protein synthesis. Indeed, during dietary energy restriction, whey protein (a fast-digested protein derived from milk that contains a high proportion of the branched chain amino acid leucine) ingestion resulted in a robust increase in muscle protein synthesis that was significantly higher than consumption of an isoenergetic and isonitrogenous amount of soy protein. During dietary energy restriction in untrained overweight/obese premenopausal women, consuming a higher protein from dairy diet combined with aerobic and resistance training, resulted in superior loss of fat mass than a lower protein, lower dairy diet, as well as gains in lean body mass.