Basically, the traditional US food pyramid is a home run when it comes to picking out foods you need to gain weight. All you have to do is increase the volume, keeping proportions the same. The pyramid is available everywhere on-line. You don’t need much science beyond that.
**IF **he tries to gain weight rapidly, his body fat % is going to increase – substantially. He is already ‘lean’, and to make gains as requested he will be packing on muscle (just to carry the heavier load) and fat, and he will get stronger if he weight trains.
**Rapid weight gain **is surely a way to increase injury to joints, ligaments, tendons and even support structures such as the spinal cord (disks, etc). Mentally, it is also a burden, as the sheer effort involved will increase stress levels and decrease his immune system’s ability to ward off illnesses.
Maybe there is some begging the question going on here. For example, I have trained teenagers, adults, middle-aged men and the most durable and rugged people I know are the leanest and most flexible people. ** You just don’t need to be an Ox to remain healthy and durable on a football field (you might find the oxen to be more injury prone and with shorter careers). **
Sure, you need to weigh a certain am’t to play lineman, but athletes continue to prove on thing over and over and over: At the ‘skill positions’, such as QB, WR, Safety, etc, sheer body weight means very little. As the NFL grew to gigundous proportions, smaller backs continued to thrive and out pace anyone’s forecast of their durability.
**Keep him lean, flexible and make sure he eats right while he weight trains – and gain mass through weight training only! ** To simply add caloric content so he can pack on the pounds is just making terrible assumptions. The extra pounds gained merely from storing excess calories are likely to have a **negative **impact on his success, not a positive one.