I disagree. There are ways of dieting in which your fat composition declines, but your muscle composition stays the same. Most diets, where you simply reduce the number of calories going in, results in a weight loss of 50% fat and 50% muscle (ie: if you lose 2 pounds, 1 pound is fat and 1 pound is muscle).
You're also making the assumption that less fat results in a healthier human being. that is also something that depends entirely on the nutrient content of your food. You can lose weight by eating nothing but small portions of white rice, but it's not going to result in a healthy individual.