Is a Pound of Muscle the Same as a Pound of Fat?

A student in my online class "Lose Weight" recently shared that a leader in a weight loss group told her that a pound of fat was essentially the same as a pound of muscle. Because we talk about the importance of strength training in "Lose Weight," and discuss the importance of muscle mass, she was perplexed, and wanted to know if there's really any difference between a pound of muscle and a pound of fat.


It's true, of course, that a pound of fat weighs as much as a pound of muscle. That reminds me of the old joke, "Which weighs more, a pound of feathers or a pound of bricks? Of course, the answer is, "Neither -- they both weigh the same! I loved that joke as a kid!


That said...Imagine how big a pile a pound of feathers would be. Now, compare that pile to 1/5 of a brick (a small brick weighs about 5 pounds). Naturally, the pound of feathers would be much larger than a pound of brick.


What we're looking at here is the difference between volume, which is the amount of space something takes up, as compared to density, which is how much something weighs. A pound of fat has the same density as a pound of muscle. However, a pound of fat and a pound of muscle don't have the same volume. A pound of fat takes up about twice as much space as a pound of muscle.


So far, we've been talking only about anatomy (how the body looks). When we turn our attention to physiology (how the body works), there's simply no comparison between muscle and fat. Muscle burns calories, even when inactive. Muscle provides structure, stability, and contributes to balance.
Fat does provide protection and cushion, and it's essential for many body processes.


But one thing many people aren't aware of is that fat doesn't just sit around. Fat is metabolically active; that is, it interacts with the body on a hormonal level. In particular, fat cells release chemicals that can result in chronic inflammation (an increase in the levels of inflammatory markers in the blood). Chronic inflammation has been linked to heart disease, cancer, Alzheimer's, metabolic syndrome, and physical disability. That's why, although some fat is required for good health, too much fat can pose health risks.


So, it's simply not true that a pound of fat and a pound of muscle are essentially the same -- even if they do weigh the same amount. It's easy to get confused by the difference between volume and density, but it's important to keep those differences separate.