Truth be told, those abilities are only going to increase if he also makes a commitment to getting into better shape.
In many ways, you could say that fitness IS self-defense. Americans are more likely to die from heart disease than assault. Your quality of life is directly related to your fitness level. Any program of self-defense, therefore, should be considered part of an overall plan to get or stay fit.
You could (and maybe should) get a gun for self defense no matter what shape you are in. Nevertheless, there are times when a gun is not available. Even if it is, studies show physically fit people have better responses to stress and will be more effective than sedentary people. Again, no one is saying you need to look like a bodybuilder to learn self-protection. It's just that fit people have more going in their favor.
Doesn't it make sense to protect yourself from disease as well as assault?