The image above is that of 5 lbs. of fat and 5 lbs. of muscle. Fat is much bulkier than 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.
Correctly said : Muscle is heavier by volume than fat
A person weighing 150 pounds with 19% fat will look much smaller (and be much healthier) than a person at 150 pounds with 35% fat. They weigh the same, yet the composition is different. Because muscle is denser than fat the person with less fat and more muscle will look smaller.
Don’t obsess with body weight and start paying attention to body composition. How much body fat do you have compared to muscle? Simply seeing how much you weigh isn’t very helpful.