I've been lifting consistently for over a month and have noticed that i'm gaining weight (unfortunately) but you wouldn't know by the way my clothes are fitting. I would think that the extra weight would be causing my clothes to be tighter. I've heard muscle weights more than fat but the doesn't seem logical...a pound of muscle and a pound of fat still weigh a pound. It seems a contradiction to gain weight and clothes to fit better, what is the reason behind this?

  • 5
    1 pound of muscle and 1 pound of fat have the same weight, but the volume is different. When someone says "muscle weighs more than fat", they're talking about weight by volume. 1 cubic inch of muscle weighs more than 1 cubic inch of fat. So it's possible that you're losing volume, which is what affects how much you fill your clothes, while still gaining weight. Sep 20, 2011 at 17:20
  • 1
    To illustrate, imagine you have 50 lbs of bowling balls and 50 lbs of of inflated beach balls. You want to put each group of balls in a box, and you want to use the smallest box possible. If you have five 10 lbs bowling balls, you could fit them in a moderately sized box. But if you had twenty-five 2 lbs beach balls, you'd need a very very large box to fit them. Sep 20, 2011 at 17:25
  • I appreciate the input.
    – rsolomons
    Sep 20, 2011 at 20:32

3 Answers 3


You're right that a pound of fat and a pound of muscle both weigh a pound, but a pound of muscle takes up less space than a pound of fat. So, if you have the same volume of muscle and fat, the muscle will weigh more. If you're working out a lot, you may be toning up and getting smaller but still gaining weight - this is because you're converting fat to muscle, which takes up less space. This article puts it pretty clearly: "muscle weighs more by volume than fat."

  • Thanks for answering. The graphic in the article you provided drives the point home. It was a good read. I provided my friend with the link - we were discussing this earlier today.
    – rsolomons
    Sep 20, 2011 at 20:34

It is important to note that in and of itself lifting weights will not cause you to gain weight. You gain weight by eating more than you need.

Exercise will change your body composition (fat->muscle).

It sounds like you have both going on.

  • Thanks for the info...Now I have to figure out the balance between eating just enough to avoid the unnecessary weight gain and still fueling the tank for energy during my workouts.
    – rsolomons
    Sep 20, 2011 at 20:37
  • Again, two distinct problems. Having energy for athletics is rarely about volume of food and more to do with the actual food eaten. A small pre-workout meal of whole-foods eaten 30 minutes prior to exercise followed with a post exercise snack of protein and carbohydrates (e.g. skim milk and a banana) is enough for the majority of post-adolescent athletes. Sep 20, 2011 at 20:47
  • I appreciate the education. This site is amazing and so beneficial. Thanks.
    – rsolomons
    Sep 21, 2011 at 12:54

First converting fat into muscle is a myth, it's physiologically impossible. Fat is made out of Adipocyte while muscle is made out of mostly proteins.

You can improve your body composition by increasing your muscle mass while decreasing your body fat but the two are happening independent of each other.

Another myth is toning. Again very similar to muscle -> fat. It's possible to achieve a 'toned' look but I prefer not to use that terms since its misleading.

As for the reason why you are gaining weight from strength training. It comes down to several factors:

  • Inflammation and water retention: lifting causes trauma to the muscle and skeletal systems which causes an inflammatory response in order to repair the damage. This leads to hypertrophy and anabolism if you eat and rest sufficiently. More specifically this causes water retention which increases your bodyweight.

  • Increased glycogen storage: any type of anaerobic lifting uses the immediate energy supply found in the muscle which is glycogen. Lifting encourages the body to store more glycogen so it's better prepared for future activity. This again increases your overall bodyweight.

  • Increased lean mass: lifting will cause you to gain more lean body mass. This isn't simply increased muscle mass but also increase in the systems that support the muscle like connective tissue. For someone on a caloric deficit you would be lucky to gain .25lbs per week, most likely less.

So there you have it, those are all the factors which impact your weight in relation to training.

  • If i build more lean muscle won't I burn more calories at rest so as long as I maintain my current calorie intake (all things being equal) shouldn't i eventually start to lose weight?
    – rsolomons
    Sep 24, 2011 at 3:49
  • It's much more complicated than that. Muscle increases your BMR but only be a small amount. So lets assume 1lb of muscle requires ~20 calories a day to maintain. And you can gain .25lbs per week. To increase your BMR by 200 calories you would need to gain 10lbs of muscle, which will take you 40 weeks. Not to mention, fat also increases your BMR, so you can argue you should gain fat in order to burn more calories. Just eat at a caloric deficit, that's the fastest way to lose fat.
    – mike
    Sep 26, 2011 at 23:11

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