Does Muscle Weigh More Than Fat?

Q. Does muscle really weigh more than fat? I am a trainer and am frequently asked this question by members of my gym. I have heard conflicting reports and can’t seem to find the right answer.

A. No, muscle does not weigh more than fat. A pound of muscle weighs exactly the same as a pound of fat—they both weigh one pound!

This commonly cited gym cliché is somewhat misunderstood and misused. The rationale that muscle weighs more than fat is often cited as an explanation for why a person might find that they aren’t losing weight, or are gaining weight, when they kick off an exercise regimen. The idea seems to be that if you are exercising—and theoretically losing fat and gaining muscle at the same time—the effects cancel each other out. So, in theory, you won’t see desired weight loss as measured by pounds on the scale, even though you may be improving how you look.

You certainly can improve your appearance with exercise without always seeing a change in your body weight—by becoming firmer, more sculpted and sometimes leaner. But that doesn’t mean that you are gaining massive amounts of muscle, or losing lots of fat.

Muscle Does Not Turn To Fat

Some people believe that if they start working out they turn their fat into muscle or that, if they stop working out, their muscle will turn into fat. Neither is true; each tissue is distinctly different. You can gain muscle or lose weight, and you can gain or lose more body fat, but they don’t convert into each other. Both gaining and losing muscle and/or fat can both affect your body weight on the scale, depending upon the magnitude of the body fat or body muscle increase or decrease.

To gain significant amounts of muscle, you not only have to do the type of exercise that stimulates muscle growth—progressive and intense resistance training—you also have to eat more calories than normal to fuel the process. Most people who exercise, especially women, do not perform resistance training at this level, nor do they eat more to try to build muscle. Even if they did, it could take many months to increase muscle mass by just a few pounds.

Body Fat Tests

Some people get their body fat tested at the gym, either by using skin calipers or a portable, step-on, body-fat scale. These measurements may show shifts in muscle-to-fat ratios, making it appear that a person has gained pounds of muscle and lost pounds worth of fat, whether or not the normal body-weight scale registers any big changes. Whether these potentially large changes in fat and muscle mass are accurate is up for debate.

On the body-fat scale, for example, you can get a dramatically different estimate of these figures from the same “weigh-in” based on whether you are input as a “normal” person or an “athlete.” So at the exact same moment a scale may show that you are at 18 percent body fat or at 27 percent body fat, for example. This large discrepancy is because the formulas used in these types of machines to calculate your measurements are based on estimates.

And there’s always a “standard deviation” in these estimated readings from calipers and body-fat scales. In other words, your result may not be as specific as you think it is, it falls within a range.

Why Doesn’t Exercise Always Affect Body Weight?

If someone is working out and not losing weight, or not losing as much as they want—or if they’re actually gaining weight—the first place to look is the type and amount of exercise.

Weight loss boils down to burning more calories than you normally use in a day. Cardio exercise burns more calories than muscle-toning or the average resistance-training workout. So dialing down the stretching and core work to just once or twice a week, and replacing it with more cardio should produce more weight loss. And the more minutes the better when it comes to weight loss: An hour to 90 minutes of aerobic activity per day on most days of the week will affect body weight.

Some people get overly obsessed about numbers on the scale. If you are happy with the way you look and feel, and you feel like you are improving your fitness and strength, then continue doing what you are doing. Exercise works, and every minute of movement helps your health in some way. Weight loss through working out may be slower than you want, but it’s likely to be longer term solution and a healthier way to trim down and shape up, or at the very least to stave off weight gain over the years.

More from Martica on MSN Health & Fitness.

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Martica is a Manhattan-based exercise physiologist and nutritionist and an award-winning fitness instructor. She has written for a variety of publications including Self , Health , Prevention , The New York Times and others. Martica is the author of seven books, including her latest, - Cross-Training for Dummies . (Read her full bio.)