Question About Building Bigger Muscles

I remember reading somewhere (on forums.thesims.com) that if you want your Sims to bulk up, you have to feed them foods with higher calories and have them lifting weights. 

If I don't want them also gaining weight from the food because of higher calories but want them to gain more muscle, do I have to make sure their hunger is in the orange or red before feeding them high calorie foods or will it not matter? 

I got one of my Sims (he'll be mentioned below) a little above the max amount of muscle on the slider but I want to make sure he doesn't get to the highest amount of body fat if possible. 

If I want bigger muscle do I have to let them reach the highest amount of body fat then have them work it off? 

Reason I'm asking is because I have a Sim of Maui from Moana (I've had him for a little over a month now) and he's from the Gallery (by a user called lucianafall) and I don't want him to get past the second scale down from the top of the body fat slider, or else he'll have a six pack and that looks just cringy on him since he doesn't have that in the movie (plus having him at the very top of the body fat slider is a bit more cringy than having it how it is now since he's not supposed to be fat). 

As for what I mean by "second scale down from the top of the body fat slider", I'll just explain it. 

So basically what I mean is that when you're in CAS and you have the body fat slider all the way at the top, you bring it one space down. 

So if I were to have him eat high calorie foods when his hunger is in the red, will he not gain weight and just gain muscle? Also like my question above, if he gains weight, do I need to have him use a treadmill and/or jog it off (since I think lowering fat in CAS will also slightly lower how big the muscles look)? 

EDIT: Had to crop them because the image was taken on my phone (I'm an Xbox player) and I couldn't get them on here because the images were too big according to the forum. 

I decided to take two pictures for reference. The first picture is the muscle size above the slider limit and the second is at the slider limit. 

I decided to take them since I thought it'd be fitting somehow for this post. But if they aren't, just ignore them. 😆