When you’re trying to lose weight, fat isn’t the only thing you lose. You lose muscle too – and that’s not a good thing for your physique – or for your health. As we age, it becomes even more important to hold onto muscle mass to avoid becoming sarcopenic. It’s no secret that you need protein to build muscle, but you also need it to prevent muscle breakdown when you’re trying to lose body fat. Now a new study sheds light on why getting enough protein is important when you’re cutting back on calories.
Weight Loss and Protein Muscle Breakdown
In a recent study published in the FASEB Journal, researchers discovered a diet higher in protein has benefits for people trying to lose weight. When you get enough dietary protein, it reduces the activity of a complex inside cells called the ubiquitin-proteasome system. The function of this system is to break down protein inside muscle cells. A higher protein diet blocks the activity of this complex and reduces protein breakdown during periods of calorie restriction. This helps you hang on to lean body mass while losing body fat.
Researchers at the University of Illinois made another discovery. If you want to preserve muscle mass while losing body fat, space your protein intake over the day instead of consuming it at one or two meals. Two groups of post-menopausal women ate a 1400 calorie diet but one group got a whey protein supplement three times a day while the control group sipped supplements consisting of carbohydrates. The women that supplemented with protein three times daily lost 3.9% more weight and had a relative gain of 5.8% muscle volume in their thigh muscles compared to those that didn’t. This doesn’t necessarily mean you need to take a protein supplement. The key is to get enough protein and consume it throughout the day.
Despite the protein supplements, the women showed some decline in muscle strength as a result of their weight loss. Keep in mind that these women didn’t do any form of exercise including resistance training so it isn’t surprising they lost strength. On the other hand, the group that got daily protein supplements showed improvements in balance.
Why Calorie Restriction Causes Muscle Breakdown
When you eat a low-calorie diet, especially a diet low in carbohydrates, your body breaks down protein into amino acids. The amino acids travel to the liver where your liver uses a process called gluconeogenesis to make glucose from them. This glucose can be used as fuel during times of calorie restriction. If you’re also doing long periods of aerobic exercise, muscle breakdown will be even greater since your body uses amino acids to make the fuel it isn’t getting due to calorie restriction. Cutting back calories too much also affects your thyroid and causes a slow-down in metabolic rate, the so-called “starvation effect.” Your body does its best to slow things down when energy is in short supply.
Resistance Training Helps to Preserve Lean Body Mass
Consuming enough dietary protein is one way to preserve lean body mass – resistance training is another. A study published in the American Journal of Clinical Nutrition showed resistance training helps to preserve lean body mass during periods of calorie restriction. This is important for a number of reasons. For one, having more lean body mass makes you strong and healthy, not frail and cachectic. Second, loss of lean body mass has health consequences. For one, it can negatively affect your balance. Finally, loss of lean muscle mass slows down your metabolic rate so you burn fewer calories with activity and at rest. This makes it easy to gain back the weight you lost. Who wants that?
How Much Protein Do You Need?
The RDI for protein for sedentary people is 0.8 grams per kilogram of body weight. If you’re restricting calories and exercising, you could need as much as twice that amount spaced over the day. The best way to get it is to have a source of high-quality protein with every meal and snack. It’s also important to consume 20 to 30 grams of protein within an hour after a workout to give your muscles the building blocks they need for repair.
The Bottom Line?
Any type of calorie restriction, especially combined with exercise, places added stress on your body that can lead to muscle breakdown and loss of lean body mass. Research shows that resistance training and a diet higher in protein, spaced over the day, helps to preserve muscle while you’re losing fat. On the other hand, aggressive calorie restriction will almost always work against you by slowing down your metabolism. Be patient when trying to shed body fat. Go for a moderate reduction in calories, no more than 500 a day and make sure the calories you’re consuming are nutrient-dense. The fast and furious approach rarely works.
Eurkalert.org. “Scientists Discover That Short-Term Energy Deficits Increase Factors Related to Muscle Degradation”
Science Daily. “Eating Protein Throughout the Day Preserves Muscle and Physical Function in Dieting Postmenopausal Women, Study Suggests”
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Am J Clin Nutr January 1988 vol. 47 no. 1 19-25.
Br J Nutr. 2012;108 Suppl 2:S105-12. doi:10.1017/S0007114512002589.
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