Fitness: Do protein supplements build muscle or fat?


Protein shakes are popular among weightlifters, but the resulting changes in body mass aren't always expected or desired.



Protein shakes are popular among weightlifters, but the resulting changes in body mass aren’t always expected or desired.


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Supplementing a tough lifting workout with a protein shake is common practice at the gym. Based on the premise that weight training breaks down the muscle and protein helps build it back up, these popular products promise to maximize the muscle-building effects of a good workout.

Containing a mix of high-quality proteins, amino acids, electrolytes and carbohydrates, most protein supplements come in powder form and are mixed with water or milk. Sold at gyms, pharmacies, grocery stores, online and at specialized nutrition stores, the shakes appeal primarily to men who believe more protein equals more muscle. But a recent study published in Science and Sports noted that too much protein can build more fat than muscle.

The researchers, who hail from France and Tunisia, hypothesized that when it comes to the use of protein supplements among gym enthusiasts, the gap between science and practice is huge. In other words, the average gym member is getting advice about supplements from peers at the gym, magazines and blogs versus more professional guidance that takes diet and gym habits into account. So while most studies in controlled conditions have shown protein supplements can be effective in building muscle, in real life their use is anything but controlled. Frequency of use, dosage and type of supplement fluctuate considerably from user to user, which has a significant impact on efficacy.

“We therefore do not yet know whether men practising resistance training in gyms truly benefit from using protein and carbohydrate shakes that they self-prescribe,” said the researchers.

To find out more about the use of protein supplements at the gym, the researchers followed the lifting and dietary patterns of two groups of male gym regulars for eight weeks. Participants were similar in age, training experience, body composition and fitness. One group finished every workout with a protein shake (maintaining their current self-prescribed dosage), while the other abstained. Both trained for 90 minutes three times a week, following an identical routine that was supervised by a trainer. They also supplied food and exercise diaries that were reviewed by the research team.

At the end of eight weeks, there was a distinct difference in the body composition of the two groups.

“Our results indicate a major body mass gain in the group consuming supplements,” said the researchers. “However, the analysis of body composition revealed that a gain of body fat was responsible for this significant difference. The group consuming supplements gained fat mass while the group who didn’t consume supplements lost fat mass.”

The unexpected gain in fat mass was largely due to the quantity of supplements consumed — up to four times the amount used in several studies where the dosage was controlled, many of which resulted in the opposite effect (an increase in fat-free mass and a decrease in fat mass).

The idea that the overconsumption of protein supplements can lead to unexpected and often unwanted weight gain isn’t new, but it’s a message that exercise enthusiasts are particularly resistant in accepting, and one that hasn’t been adequately illustrated until now.

Ideally, the amount of protein supplements consumed should be based on current diet and exercise habits. Exercisers who already consume lots of good-quality protein (beef, eggs, milk, yogurt, etc.) and spend a moderate amount of time in the gym likely have all the protein they need to promote adequate muscle repair and growth.

The Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine recommend 1.2 to two grams of protein per kilogram of body weight each day for athletes, depending on training volume. Yet the amount of protein consumed by the exercisers in the study was closer to 2.4 grams per kilogram of body weight, irrespective of the volume of training — hence the unexpected gain in fat mass.

“It appears that in practice protein supplements are not considered by consumers as nutrients, and are consumed without taking into account food dietary intakes, which leads to overfeeding,” said the research team. “The increased calorie content through protein supplements could not be offset by the energy expenditure of our amateur men practising resistance training in the gym.”

Supplements, as the name suggests, are designed to complement a diet that can’t meet its needs through food. As such, they should contain nutrients not readily available in your daily diet, or help adjust calorie consumption to achieve goals related to body composition. An imbalance in the type or volume of nutrients consumed will lead to less than ideal results.

The best person to help guide gym enthusiasts toward the proper use of protein supplements is a registered dietitian. Outside of getting professional advice, sticking to the product’s recommended dose is likely to offer sufficient stimulus to help muscles recover after a tough workout. But what the French/Tunisian study so eloquently illustrated — and a take-home message worth repeating — is that when it comes to supplements, more isn’t always better.

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