Last updated on July 9, 2026
Question:
Hello again.
I have another question, this time about my weight. I’ve heard that in your late teens, you begin to “fill out” and gain weight. Seeing as I’m in late stage 4 at 16 years old, when do you think I’ll probably start to fill out? Approximately how much weight will I gain, and in how short a time?
Answer:
When you are in stage four, your body can build muscle. You can get strong when you’re younger, but there’s essentially a peak to how strong you can get because all you can do is strengthen your existing muscle fibers. Beginning in stage four and continuing for most of your adult life, you can increase the number of muscle fibers in your body through exercise. The amount you gain will depend entirely on the amount of exercise you do. Unfortunately, it is not a one-way street. If you stop exercising or decrease the amount of exercise you do, your body breaks down the extra muscle fibers.
Therefore, with exercise, you can build up big biceps and thighs. You can also get “washboard” abs, but those won’t be seen unless your overall body fat is low. Body fat ruins muscle definition by filling in the valleys between muscles.
When you reach stage 5, a different problem arises. You stop growing, but a lot of guys keep eating like they are still growing. Thus, they fill out — around the middle — with fat.