3 Keys to Preserving Muscle Mass When You Lose Weight

lose weight not muscle mass

When you lose weight, the composition of that weight loss matters. Ideally, you want to lose fat while retaining your muscle but that’s not the way it typically happens. Along with fat loss, you usually lose varying amounts of skeletal muscle.  How much fat you lose relative to muscle depends on several factors. If you have a lot of body fat, meaning you’re significantly overweight, you’ll lose more fat and retain more muscle than a relatively lean individual who has less fat on their body to begin with. Genetics are a factor too. Some people are genetically primed to hold on to body fat at the expense of muscle when they lose weight. However, diet and the type of exercise you do are the most important modifiable factors. Here are three ways to limit muscle loss when losing weight.

Stimulate Your Muscles

Most people think they should do hours of calorie-burning cardio to lose weight. Yes, you need some cardio in your routine for heart health, but for preserving muscle mass, strength training rules! Intensity matters as well. You might think using lighter weights and doing high reps burns more calories but lifting heavy creates the anabolic response you need to preserve muscle when you’re dieting. Using a heavy resistance also creates more of an after-burn, so you continue to burn more calories after a strength-training session is over. That’s favorable for fat loss too. So, focus on compound exercises, movements that work multiple muscles at the same time, like deadlifts, squats, lunges, push-ups, bench press, pull-ups to prevent muscle loss.

Boost the Protein Content of Your Diet

The Institute of Medicine recommends getting 10 to 35% of your calories from dietary protein. Sedentary people fall toward the lower end in terms of protein needs while athletes should consume toward the higher end. As you know, protein provides the building blocks (amino acids) for repairing and building muscle tissue. To preserve muscle tissue, your muscles need access to these basic building blocks of muscle. A higher protein diet supplies them.

Does science support this idea? In one study, researchers asked a group of overweight participants to consume various amounts of protein while they followed a low-calorie diet. One group ate a diet where protein made up 10% of their calories. The second group consumed double that amount and the third group triple. In all, the first group took in 50 grams of protein daily while the second and third consumed 100 and 150 grams daily respectively. All the participants lost weight, an average of about 2 pounds per week. But the participants who consumed more protein lost less muscle than the group who ate a 10% protein diet. So, a higher proportion of the weight they lost was fat rather than muscle.

One caveat of this study is the participants were already consuming a relatively low-protein diet. If you’re accustomed to eating a somewhat high protein diet, upping your protein may not have the same impact. Also, we can only extrapolate the results to people who are calorie restricting to lose weight, not to people who aren’t dieting. Still, it points out the importance of consuming enough protein when you’re cutting back on calories, especially if you’re physically active.

Getting more long-chain omega-3’s from fatty fish in your diet may help you hang on to more muscle too. Think wild-caught salmon, sardines, and anchovies! Some studies show that omega-3’s help to suppress catabolic hormones, like cortisol, and turn on anabolic pathways, such as the mTOR pathway that activates muscle protein synthesis.

Don’t Lose Weight Too Quickly

Losing weight fast sounds desirable, but when you shed pounds too quickly through excessive calorie restriction and overzealous exercise, it places more stress on your body and your body perceives starvation. It reacts to that threat by slowing your metabolism, a phenomenon called adaptive thermogenesis. Unfortunately, the slowdown in metabolism that comes from extreme weight loss practices doesn’t reverse quickly.

Remember the show The Biggest Loser? A study published in the journal Obesity looked at the outcome of 16 people who lost substantial amounts of body weight due to extreme dieting and exercise. These folks were part of The Biggest Loser weight loss competition. Not surprisingly, the participants lost weight, but how did they fare longer term?

In the study, researchers measured their resting metabolic rate and body composition 6 years after their initial weight loss. Not surprisingly, the participants regained significant amounts of weight. But, despite the weight regain, their resting metabolic rate was still 500 kilocalories per day lower than you would expect based on their body composition. Those who lost the most weight had the greatest slowdown in resting metabolic rate. What’s surprising is adaptive thermogenesis in response to the weight loss persisted 6 years after they shed the extra pounds and even persisted after they regained the weight. It adds some credibility to the idea that you can damage your metabolism long term through aggressive weight loss practices.

Weight regain is one thing, but what about muscle loss? Extreme dieting and long periods of cardio ramps up the release of cortisol, a stress hormone made by the adrenal glands above your kidneys. In turn, cortisol triggers muscle breakdown. The long-term effect of too much cortisol can be an unhealthy loss of muscle tissue. So, lose weight in a healthy manner and give the process time. You’ll still get there, and you’ll be healthier for it!

The Bottom Line

The number on a standard scale represents your total body weight, including the weight of your organs, muscle, body fat, glycogen stores, and how much fluid you’re carrying in your body. But the only weight that counts is the loss of body fat. If you lose a high proportion of muscle relative to body fat, you’re not doing anything positive for your body. In fact, loss of muscle mass can make you less functional and lead to frailty in an older person. That’s why it’s important to lose weight at a reasonable rate, make sure you’re consuming enough protein, and work your muscles against resistance. Doing these three things will help you lose more body fat and less muscle.



Obesity. Volume 24, Issue8. August 2016. Pages 1612-1619.

Quick and Dirty Tips. “Double Your Protein, Lose More Fat”

Clin Sci (Lond). 2011 Sep;121(6):267-78. doi: 10.1042/CS20100597.

Int J Obes Relat Metab Disord. 1996 May;20(5):393-405.


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