The recommended way to do this is to eat healthy foods in amounts that are more than your body needs. Eating unhealthy foods would also add to your weight but might harm you in the long run.
If you want muscle-mass more than fat-gain, you'll also need to get plenty of exercise.
Healthy foods to gain weight:
- red meat; fish (especially oily fish such as sardines)
- seeds and nuts; peanut butter, almond butter, tahini
- dairy and eggs
- sweet fruits such as mango, banana and papaya
- avocado
- granola; dried fruit; protein bars
- whole wheat bread; whole grain breads, crackers and foods; legumes
- olive oil on salads or wherever appropriate
- carbohydrate-veggies such as potatoes and yams
Don't overdo it. Gaining weight faster than about 1 pound per week should be done under supervision.
