Weighed him this afternoon, so now let's make that 137 lbs. His summer team dedicates a lot to weights & training, so I'm hoping that fits the bill. But I will definitely put him with someone who knows baseball players needs.
The problem with my son is gaining weight. He's a modest eater, but I can't stuff it down him. He gags on protein shakes... all 173 of them we've tried. But, we got good advice from his Dr. the other day so I thought I'd pass it along... "Ensure Plus" (8oz 350 calories, 13g protein). He just started with them, but he likes them easily enough to drink 2 per day. Any other suggestions for a picky eater trying to gain?
He likes Ensure Plus, but doesn't like any of the protein shakes? Have you tried mixing a decent tasting chocolate whey protein with whole milk instead of water? Much richer and better tasting, and you get the additional calories of the milk. Put it in the freezer for an hour or two and you get a chocolate milkshake, but with 25g+ of protein.
Someone mentioned peanut butter, which is a good idea. You can also pretty easily mix olive oil into pasta, rice, or potatoes. Do that at each meal and it starts to add up.
Everyone has different metabolisms, so it's tough to give a generic recommendation. But a starting point of 150g/day of protein, 300g/day of carbs, 100g/day of fats equates to about 2700 calories per day. Do you think he would lose or gain weight at 2700 calories? Is he capable of eating that much?
This thread is taking a very different path than the original question, but I just want to add one more thing. Whatever path you go down nutritionally, think long-term as well. Just like focusing on academics so there is something to fall back on when baseball careers are over, have a good sustainable nutrition plan that sets him up for a healthy lifestyle after baseball is over. This isn't wrestling or other sports where obsessive and/or unhealthy eating habits need to happen.