Muscle Myths and Fat Facts

( [email protected] ) Nov 03, 2007 11:44 AM EDT

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Have you ever wondered how long and how intensely you would have to train to turn all that loose body fat into toned muscle? When you stop training, how long will it take before the muscle turns back into fat? Do sit-ups and crunches truly get get rid of your belly and leave you with a firm six-pack? Is it possible to lose fat but not bulk up from weight training?

As a health educator I hear questions like this often. In fact, they have been asked so frequently that I’ve realized there is a significant lack of knowledge relating to how training truly affects body composition. To be able to answer any of the above questions we need to first understand the different roles of body fat and muscle.

Muscle metamorphosis

To begin, it is essential to clarify that it is a complete myth that you can turn fat into muscle with training. Body fat and muscle are two completely different tissues. They have different structures and functions, they react to training in different ways and, simply put, one does not have the capability to turn into the other. Let’s look at each individually:

Body fat

Body fat is completely related to calories, and the amount that we have is directly influenced by the number of calories consumed versus calories expended. Calories consumed obviously come from the foods we eat. It is important to recognize that when we consume any type of food in excess, whether it is carbohydrates, protein or dietary fat, it will be converted to body fat.

The flip side of the equation is calories used or expended. This brings exercise to mind, however, your body also expends calories in other ways. We focus on exercise because it is the method that can be most easily manipulated. Any form of exercise, at any intensity—aerobic training, resistance training, going out for a walk or performing a spring workout—burns calories and is, therefore, better than doing nothing at all. With all of this in mind, it is also important to understand that those thousands and thousands of individual fat cells that give us those nice love handles act as one unit and essentially have three options:

- to grow and possibly divide;

- to rest as is; or

- to shrink in size.

The option your fat cells will choose completely depends on the calories you consume versus the calories you burn in your daily activity.


Muscle is very different from fat. Each muscle is made up of thousands of individual cells, also called muscle fibers. While the number of muscles cells/fibers can not increase, each individual muscle fiber has the potential to increase in size, density and efficiency. These changes may occur together but not necessarily to the same degree, however, all will translate to an increase in strength.

Unlike fat, strength gains are not related to calories; changes in the muscle physiology and resulting increases in strength do not occur as a result of dietary intake. Assuming you are eating a well-balanced diet, changes within your muscles are most influenced by the direct stresses that you place on each of them individually. These stresses can be through job-related activity, daily chores, aerobic activity or strength training. The key factor is that the muscle will only react if the stress placed on it exceeds the everyday stress it is accustomed to.

Again, this doesn’t mean you need to get to the gym and start lifting weights, however muscle is often associated with weight/resistance training because this is the easiest way to control and monitor the stress being placed on the muscle. It is also very effective because you can isolate any muscle and do so in a safe environment.

To help answer your fat vs. muscle questions, take a look at these quick summaries:

Quick Summary of Fat

- Fat can not become muscle and muscle can not become fat.

- Fat can only be reduced if the number of calories expended in a day exceeds the number of calories consumed in a day. Fat will be gained if the opposite occurs.

- If you stop training, but compensate for this with a slight reduction in diet, your body fat will not increase.

- If you begin training but also increase your dietary intake, you can gain fat.

- Fat cells act as one, meaning you can not choose where you lose it or gain it.

Quick Summary of Muscle

- Changes in muscle size, density and/or efficiency cause an increase in strength; however, these changes only result if the muscle is stimulated beyond what it is accustomed to.

- Weight training is the easiest way to control and monitor the changes in your muscle physiology. By manipulating your sets, reps and weight lifted you can achieve various responses. Because of this, it is possible to increase your strength without adding bulk, and it is also possible to increase both.

- When you stop stimulating the muscle, your muscle composition may return to normal or, depending on your regular routine, it may simply stay as is.

- Unlike fat, each muscle can be specifically targeted, so you can choose the specific area you would like to improve. With that said, realize that while you can work your abdominal muscles, for example, you may not see the enhanced shape and form if you have a thick layer of fat covering them up.