A randomized study evaluated whether same-day protein intake is best consumed at one high-protein meal, or spread over the day with reference to muscle growth.
Body composition refers to the relative abundance of fat, bone, and muscle in our bodies expressed as percentages. Weight loss plans are generally designed with the goal of inducing positive changes in body composition—namely, reducing fat while maintaining muscle mass. It has been proven that eating more protein daily helps preserve muscle mass and improve body composition.
In the last ten years though, it has been speculated that not only is the amount of protein important but its distribution throughout the day as well. The idea is that instead of eating most of the daily protein intake at one meal (skewed distribution), the individual splits the total protein intake over three meals (even distribution). Because little research has been conducted on the topic, an American group set out to assess whether same-day protein intake distribution helps maintain muscle mass during periods of weight loss. The results were recently published in The American Journal of Clinical Nutrition.
The randomized study consisted of 41 men and women, all of whom were subjected to a calorie-restricted diet—750 kcal per day below the recommended requirement—as well as resistance training three days a week. Participants consumed 90 grams of protein a day in either a skewed (10 g at breakfast, 20 g at lunch, and 60 g at dinner) or even (30 g each at breakfast, lunch, and dinner) distribution pattern. Body composition was measured before and after the 16-week intervention period. In addition, mid-thigh and mid-calf muscle area measurements were taken at the same time-points.
In the end, while all of the subjects lost weight, both groups showed a decrease in lean muscle mass. As such, it was concluded that same-day protein intake distribution did not result in the predicted body composition responses. The researchers tentatively attribute this to fact that the amount of protein designated at each meal between the even and skewed distribution groups did not differ enough to induce any significant lean body mass changes. It is also plausible that the skewed group may have consumed enough protein at lunch and dinner to maximize the muscle protein synthesis (MPS) process. The diminished MPS rate after breakfast may not have been enough to substantially affect muscle mass enough to be detectable given the study’s design.
This is the first randomized controlled trial to use strict dietary and resistance training to assess the effectiveness of an even or skewed protein distribution on body composition. The results showed that, contrary to the hypothesis, protein intake distribution did not affect body composition in adults undergoing weight training. Perhaps further research with larger sample sizes and longer intervention periods may shed more light on this topic. However, until then, you can likely skip the hassle of meticulously planning your individual meals’ protein contents. Combined with a healthy diet and exercise routine, improvements in body composition can be attained as long as you are reaching your daily protein intake goal.
Written by Rebecca Yu
Reference: Hudson, J. L., Kim, J. E., Paddon-Jones, D., & Campbell, W. W. (2017). Within-day protein distribution does not influence body composition responses during weight loss in resistance-training adults who are overweight. The American Journal of Clinical Nutrition, ajcn158246.