If you've been around bodybuilding for as long as I have (over half a century) you will notice that people who get involved in regular bodybuilding training seem to make gains at different rates. Much of this has to do with genetic predispositions that favor rapid muscular growth. An example of this is the body type known as a mesomorph. Body types are divided into three categories: those who are naturally thin are called ectomorphs; Those whose natural body type veers towards excess body fat are endomorphs; and those who seem naturally muscular with low body fat levels, wide shoulders, and a smaller waist are the mesomorphs. Although these classifications may be useful for scientific purposes, in reality, you rarely find pure versions of any particular body type. Most people are a mixture of the body types, such as endo-meso, or ecto-meso. It's obvious that basic body types can be altered by the extent of physical activity and diet. For example, you can start out being thin, or ectomorphic, but if you overeat and don't exercise to burn off the excess calories consumed, you can slowly convert your basic ectomorphic body type into a heavier endomorphic type. Much of your natural body type is related to bone structure, with ectomorphs having a smaller overall bone structure compared to endo and mesomorphs. Hormones also play a role. Those who exhibit a more mesomorphic appearance often show naturally higher testosterone levels compared to the other two body types.
In my experience from interviewing thousands of elite bodybuilders over the years when I wrote for a number of bodybuilding magazines and attended various bodybuilding contests around the world, most champion bodybuilders tend to be a combination of ecto-mesomorphs. What this means in simple terms is that they are thin when they begin training, but pack on muscle once they start regular training. Having this particular combination of ecto-meso body types is a definite advantage for competitive bodybuilders since the ecto portion comes with small joints, hips, and waist structure. As they build muscle mass, these areas such as the hips and waist stay relatively small, thus emphasizing the muscle mass of the rest of the body. This doesn't mean that those who are endomorphs or tend to gain fat more easily have no chance of success in bodybuilding, but rather that it's more of an uphill climb for such types. The reasons for this include the fact that endomorphs tend to have a larger and greater quantity of fat cells. This makes it harder for them to acquire the extent of muscularity required to compete in a top-level bodybuilding competition. They also tend to have wider waists, again not an asset to having a championship physique. But those problems can be overcome with stringent dieting and training. I recall seeing photos of a woman taken before . . .