Yeah, that's probably the problem honestly.
A young male needs AT LEAST 3000-3500 calories a day, easily 4000 or even more if active at all.
Assuming 200g carbs, 90g protein, and let's say 30g fat, puts you at like 1500 calories. WAY too low. Need *at least* twice that, and possibly more. 90g protein is sufficient if sedentary, and in the context of sufficient overall calories. However on a low calorie diet, that low protein intake is probably catabolized for glucose.
I'm fat, so I know my numbers aren't necessarily the optimal comparison point, but I eat 900-1,000 grams of carbs a day. I would literally die on only 200 a day lol.
Vitamin supplements are literally useless in the absence of sufficient calories.
I gain weight VERY easily and the truth is on Paleo I ate 3000 calories easily, mostly from fat but there's no way I can do that with a diet that is relies on carbs for energy.
Protein is a very difficult one, white fish and chicken breast are my staples. Eggs once a week and oysters act as a supplement.