im not a doctor but if you want to pack on size eat a peanut butter sandwich every hour and do 50 pushups every half hour.....

in 2-3 months people will ask if youve been working out....

Heh that is one way of doing it. Not necessarily just peanut butter sandwiches though, you still want to keep a balanced diet, plus you get sick of eating it. Eating something every hour (though small) can be difficult, but you could try to eat something every 3 hours. A turkey sandwich, peanut butter, tuna (not too much considering the precautions lately with high concentration of mercury), whatever really that has a good source of protein or carbohydrates. Be sure to work out though, or you will just get tubby. Though unhealthy, eat later as well, but an hour or so before you go to bed (nothing huge though) like that peanut butter sandwich the previous poster was talking about.

Hmm I disagree with rmb...

Buy some dumbbells or join a gym.. Pushups will only do so much, unless you add weight resistance, it will mostly build endurance. Eat a load, and make sure you rest between workouts. Mikolas' post is spot on. If you want to bulk up don't be worried about getting a little tubby, eat canned beef, steak, whole milk.. you can always run off the fat later on, and you'll still regain the muscle.

Also.. "powdered drinks".. Protein powder is a NATURAL way ... Bodybuilders just struggle to get their required protein intake through normal foods so they take supplements.