Which weighs more - muscle or fat?

This is a common myth. The easiest way to understand this is to look at it this way...

5 lbs. of fat is much bulkier than the 5 lbs. of muscle, but five pounds is still five pounds. Muscle does not weigh more than fat.

Fat is bulky and lumpy so if you carry an extra five pounds of fat, you'll be lumpier than with five pounds more muscle. A five pound pile of fat will take up more space (volume) than a five pound pile of muscle; but five pounds is still five pounds.

A woman weighing 150 pounds with 19% fat will look much smaller (and be much healthier) than a woman at 150 pounds with 35% fat. They weigh the same, yet the composition is different. Because muscle is more dense than fat the person with less fat and more muscle will look smaller.