Weight loss or improving body composition?

Many people wanting to improve their looks or their health seek to lose weight achieve this goal by dieting, a dedicated training planĀ or both. Often they set goals to lose a certain amount of weight. Others don’t use the scale to measure their progress, but look towards body fat calipers or other methods to assess their body composition. So the important question is: Which is better focussing on weight loss or improving body composition?

The advantage of setting a weight loss goal is that it is easy to measure weight. However, the weight lost can be caused by loss of fat mass, muscle mass, water or a combination of these. Measuring body composition allows to keep track of changes in the relative amount of fat during diets and weight loss training programs. Changes in body fat percentage better represent changes in someone’s health and fitness. As stated above, weight loss can also be caused by a loss of muscle tissue. This not only makes a person weaker and less fit, resting metabolism decreases as well. This makes retaining weight loss much harder.

Consider the following example:

Subject 1 and Subject 2 before weight loss:

Table 1 Subject 1 and Subject 2
Age 25 years
Length 182cm/6′
Weight 90kg/200lbs
BMI 27.2 (overweight)
Fat Percentage 25%
Fat Mass 22,5kg/50lbs
Fat Free Mass 67,5kg/150lbs

Subject 1 and Subject 2 followed different weight loss programs and the results are:

Table 2 Subject 1 Subject 2
Weight 82kg/182lbs (-8kg/-17.8lbs) 88kg/196lbs (-2kg/-4.4lbs)
BMI 24.8 (Healthy) 26.6 (Overweight)
Fat Percentage 23% (-2%) (Overweight) 18% (-7%) (Healthy)
Fat Mass 18.9kg/42lbs (-3.6kg/8lbs) 15.8kg/35.1lbs (-6.7kg/14.9lbs)
Fat Free Mass 63.1kg/140.2lbs (-4,4kg/9.8lbs) 72.1kg/160.2lbs (+4.7kg/10.4lbs)

In this example we can see several interesting things. First, Subject 1 lost more weight in total and therefore was no longer overweight according to the BMI. However, his fat percentage did not decrease as much and he is still considered overweight in this respect. This means that, although he did manage to lose some body fat, most of the lost weight was not fat, but muscles and water instead.

Subject 2 on the other hand did not lose as much weight, but did manage to bring down his fat percentage by a considerable amount. Enough to be classified as healthy when looking at fat percentage. The BMI in contrast, which depends only on weight and length, still classifies him as being overweight, even though the health risk as a result of too much fat has decreased considerably. Subject 2 managed to lose a lot of fat and actually gain some muscle mass. Not only does this make him look a lot better than Subject 1, he is healthier as well.

This example serves to illustrate that it is better to improve body composition, than to just focus on losing weight. Someone who gains muscle mass and burns fat mass at the same time, will look healthier and lighter than they actually are. Muscle tissue density is much higher than fat tissue density, meaning that in the example above Subject 2 looks a lot slimmer than Subject 1 despite being heavier.

See also:

-Is Cardio Training the Best Way to Lose Weight?

-Strength Training for Weight Loss

-Cardio Training for Weight Loss