Post-exercise Supplement Reduces Muscle Loss

One of the main challenges for people who want to lose weight is to get rid of the fat without losing muscle. The good news is that a post-exercise supplement can help to minimize the loss of muscle during a restricted-calorie diet.

In one study, a group of ten active young women took part in two separate seven-day trials separated by at least one week [1]. The women cycled at approximately 65% of their VO2peak on four days (day 1, 3, 4, and 6). On day seven, they performed a ride to exhaustion at approximately 75% of VO2peak.

In trial one, the women took a carbohydrate-protein supplement after exercise. For trial two, they consumed a placebo supplement that contained no nutrients. Nutrient intake over the course of the week was the same; it was only the timing that differed.

The women lost weight during both trials: 3.1 pounds (1.4 kilograms) during the control condition, and 1.5 pounds (0.7 kilograms) when using the supplement. Unfortunately, the researchers didn't measure body composition, so we don't know how much of the lost weight came from muscle and how much came from fat.

Nitrogen balance was positive on day five and six when the women used the post-exercise supplement. Without the supplement, nitrogen balance was negative.

Nitrogen is found in foods that contain protein (such as fish, meat, poultry, or dairy produce). Nitrogen balance represents the difference between the amount of nitrogen you consume, and the amount of nitrogen you excrete.

A positive nitrogen balance is thought to indicate an anabolic state (muscle growth) while a negative nitrogen balance indicates catabolism (muscle loss).

Although the positive nitrogen balance suggests that using the supplement after exercise helped to preserve muscle, there are problems with using nitrogen balance to estimate muscle loss.

Moreover, we know that protein metabolism in women varies according to the phase of the menstrual cycle they're in [2, 3]. For five of the women, the trials occurred on successive weeks, and for the other five, on successive menstrual cycles. This may have influenced the nitrogen balance measurements.

Reference
1. Roy, B.D., Luttmer, K., Bosman, M.J., & Tarnopolsky, M.A. (2002). The influence of post-exercise macronutrient intake on energy balance and protein metabolism in active females participating in endurance training. International Journal of Sport Nutrition and Exercise Metabolism, 12, 172-188
2. Lamont, L.S., Lemon, P.W., & Bruot, B.C. (1987). Menstrual cycle and exercise effects on protein catabolism. Medicine and Science in Sports and Exercise, 19, 106-110
3. Bisdee, J.T., Garlick, P.J., & James, W.P. (1989). Metabolic changes during the menstrual cycle. British Journal of Nutrition, 61, 641-650