paulflexes saidFor a naturally thin person with super-high metabolism:
High carb foods (complex carbs)
High protein (peanut butter, eggs, etc.)
Also, hiring a trainer would be a great idea. They can help tailor your food choices, as well as get you started on a workout program that will build mass. You've already got great definition to work with, so bulking it up shouldn't be too difficult. Just don't forget to maintain it once you're there...it can be lost just as easily as it's gained.
No, it can be lost easier than gained. To gain it you will have to work your ass off to get big. Maintenance is going to be the challenge once you get there. Your body is a muscle eater by nature due to the high metabolism.
So eat real food, stay away from the protein shakes your body will look better (though you will shit something awful). Stick to protein shakes before and after workouts only. If you can sub the protein shake before the workout with some eggs and oatmeal or something even better.
Try to eat every 2-3 hours, carbs (don't cut back on this or your body will use the protein as an energy source) -- here are some I find really easy to eat/prepare are yams (they taste good cold), Pasta (whole wheat), Whole wheat bread: Protiens: Chicken, Beef, Pork, Tuna (cheap and easily accesible). Eat fruits.Drinks lots of water, and try to sleep as much as possible.
Work out 3-4 times a week no more than that. If you get fat(relatively ie you have body fat) do cardio rather than change your diet. 20-30 minutes should get rid of the fat. Though you shouldn't worry about it too much. It'll take one day of you eating a little less to lose it but your body will probably burn the muscle too. Get a trainer. Helps tremendously. And lastly be happy with your body. You are hot :-)