I don't study anything related to health and/or nutrition but like, shouldn't growing boys and girls eat more? Why is he restricting himself so bad?
thanks for translating this oneshot btw!
Well, yes and no. Whether you're a growing adolescent or not, if you want to build muscle, you can't restrict your calorie consumption too much. You need a daily calorie surplus, otherwise your body thinks you're starving and won't spend precious nutrients on building more muscle mass (which in itself requires a lot of nutrients to maintain). So his whole idea of training to build muscle as well as restricting his calories is kind of flawed. Granted, there's no point in having too large of a calorie surplus, it should just be enough to put your body into muscle-building mode. Also, even if you need a calorie surplus, there's no point in eating unhealthy food with a lot of saturated fat like deep-fried chicken. But, if he controlled his diet properly and ate enough to get that calorie surplus from healthy sources, he wouldn't have any trouble resisting her temptations, because he wouldn't be hungry.
If you want to get shredded, you also need to cut your fat at some point and then you do need to restrict your daily calories down to a deficit, but then you don't build any new muscle, you just maintain the muscle you already built, and you only wanna do that when you actually have significant muscle mass already. The MC in this manga is way too small and skinny for it to be advisable for him to do that yet. It's also probably not a good idea to try while you're still growing (unless you're very overweight, which he clearly isn't).