To better understand the difference between the two, let’s have a quick review about body composition. In essence, our bodies are made up of a few major components:

• Fat mass is the weight of all the fat molecules in a person’s body.
• Lean body mass and fat-free mass are terms that people may use interchangeably to refer to the non-fat molecules in the body. This includes most of the mass of internal organs, bones, muscle, and more, as well as all the water in the body.

Having too much fat in proportion to lean muscle tissue contributes to obesity and ups your risk for chronic health problems like diabetes, high blood pressure, high cholesterol, and heart disease. Body fat percentage recommendations vary based on age, sex, and activity level. According to the American Council on Exercise, healthy body fat levels range from 14 to 31 percent for females and 6 to 24 percent for males — but only athletes should be at the low ends of those ranges.

Most of the time, when we talk about wanting to lose weight, we’re really talking about wanting to lose fat. This is not only because excess fat is potentially dangerous but also because you don’t want to get rid of muscle tissue.

Losing muscle can be detrimental, as muscle is a crucial component of your overall health. Muscle tissue gives you strength and actually helps your body burn more calories.
Additionally, the more muscle you have, the more calories you burn at rest. This is the main reason why men generally have higher calorie needs than women.

In summary, emphasizing fat loss not only leads to overall weight loss, but it can also help decrease the risk of several chronic diseases, reduce the risk of age-related muscle loss, and reduce fat regain.