Does muscle turn into fat as I age?

Muscle  and fat are two different substances. One will never turn into the other. As we age we typically become less active. This can be for a variety of reasons from decreased balance and vision problems to hip and knee arthritis issues. The decrease in movement will cause your  body to break down muscle tissue. If  you don't use your muscle tissue, it will atrophy and you will lose it. As muscle begins to break down, your  metabolism will also start to decrease. If you do not decrease the amount of calories you are consuming, then  you will start to store the excess calories as fat. It is important to stay as active as  possible. If balance and joint pain  are the issue, work with a certified personal trainer on ways to combat these  challenges. Research has proven that  aging does not mean that your muscles stop working or that you have to get fat. Resistance training is great way to help slow down the reduction of muscle tissue and possibly even increase muscle mass.

Wendy Batts

Muscle and fat are two very different body tissues, so one doesn’t turn into the other. However, we do tend to lose muscle mass and gain fat as we age. This is in large part due to the decline in physical activity that comes with age. As we get older, we often participate less in athletics and recreational activities and spend more time sitting at work, during our commute, or on the couch. Remember, if you don’t use it, you lose it! This coupled with high calorie foods that are readily available, leads to the common weight gain associated with age. The best way to reverse this is to sensibly increase your physical activity and reduce your calorie intake.

Dr. Michael Roizen, MD
Internal Medicine
Not exactly, but yes you replace muscle with fat as you age if you do nothing about it. The more active you are with resistance exercises, the more muscle you build, and the more fat you burn.  So even as you age, keep up your 10,000 steps a day.  No excuses!
You cannot change fat into muscle and vice versa.  Unfortunately as we age we start to lose muscle which in turn causes us to gain more body fat.  Muscle is what dicates how are metabolism is so the more muscle we have the more calories we will burn.  If we start losing muscle our metabolism starts to slow down and we increase bodyfat.  That is why weight training is so important to our everyday routine.

The good news is that muscle cannot turn into fat as you age because they are completely different tissues.  That is one of those myths out there that people like to believe, especially because it seems like muscle does turn into fat as we get older. Instead, most people simply lose muscle mass (usually through inactivity) and gain more body fat as they get older, though a combination of more calories, less movement and a slower metabolism. The fat actually can replace the space where the muscle tissue used to be. Luckily, you have the power to fix this. Make sure your workout routines incorporate strength training at least 2 times per week. By maintaining muscle mass you will have an increased metabolism, a lower body fat percentage, and participating in weight bearing activities is also good for bone health.

Dr. Mike Clark, DPT
No, muscle and fat are two very different tissues in your body and they cannot morph into one another. Aging comes with many physiological changes; however you can reduce deleterious muscle loss and fat gain by staying active throughout your entire life span. As you age, muscle begins to break down (a condition called sarcopenia) and you may tend to gain more fat since you are not as active, and likely, have not changed your eating habits to match your reduced activity levels. Without knowing it, you end up eating more than you move and your lean muscle begins depleting as your fat stores expand. In essence, fat begins to replace muscle as you age. However, the good news about this is that you can slow down muscle loss and increase health by staying active for at least 30 minutes a day, 5-7 days a week. Whether going for a brisk walk, participating in your favorite sport, physical hobby or becoming involved in weight training, you can maintain the muscle you have longer and stay healthier by making movement a part of your lifestyle.

Fortunately, muscle cannot turn to fat as you age.  What normally happens is a combination of muscle loss, decreased activity and increased caloric intake.

If someone stops training or being active then their muscles will atrophy, which simply means they will shrink over time due to the lack of physical activity. Sarcopenia, on the other hand, is the normal loss of muscle mass as we grow older, which is why it is important to be as active as possible.

Another factor to consider is the Principal of Reversibility, which simply means that you need to move it or lose it. Unfortunately, any of the gains your body has made through training will be lost over time if activity stops. This applies to aspects of strength, flexibility, cardiorespiratory fitness and muscle mass. Rest is necessary to ensure proper recovery, but extended time off will whittle away at your gains over time.

Please remember, the greater amount of lean body mass/muscle you have, the greater your metabolism will be. Simply put, more muscle means that you burn more calories. So if you stop training for long periods of time you are essentially slowing your metabolism and lowering the rate at which you burn calories each day.

The number of calories consumed daily is another concern. If you are accustomed to doing a certain level of activity and you stop, but you continue to eat the same or greater number of calories as before, then those calories will be stored as fat.  In most cases it is probably a combination of the two, less physical activity combined with over-eating.  Unfortunately, there are so many high calorie food options available that it is easy to eat too much if you don’t follow a balanced diet.

Key Points to Remember:

  • Don’t be fooled by the notion muscle can turn to fat
  • Weight training and cardiorespiratory activity help build and maintain muscle, while burning calories
  • Lean muscle mass increases the rate you burn calories
  • If you consume more calories than you burn they will be stored as fat
  • Remember the Principal of Reversibility, use it or lose it
  • Get out there and be active!


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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.