@tennosea- I also believe that your advice is well-meaning, but I don’t think either of the teenage guys in this thread are in danger of getting too skinny. Unless they are both very tall and muscular, 188 and 215 are pretty heavy weights for guys just out of high school. Note that I didn’t say they should give up the McDonald’s and pizza, but exercise is important, for many reasons including nutrient partitioning. If you don’t exercise, excess calories are going to turn into fat, and that’s only useful if your body fat is too low.
I know from experience that it’s a lot harder to get into shape if you’ve been sedentary for a long time. After a certain point, extended rest just makes you weaker.