The answer you're looking for is body composition. This term is used to describe the percentages of fat, bone, water, and muscle in human bodies. When someone has a lower percentage of body fat and a higher percentage of non-fat mass (muscle, bone, and water), we can say that they have a healthy body composition.
This is why we can't just rely on weight as a measurement of our physical condition. Two people of the same gender and body weight can look completely different because they have a different body composition.
