There is a Martial art that'll get you "fat" in no time - take up Sumo Wrestling! They are amazing wrestlers!
I both love, and am very attacked by that picture. As to the OP, it does depend on why you'd want to put weight on. I'd be very unlikely to say to a person that they NEEDED to put fat on for the sake of health, as it's very rare that someones bodyfat is naturally that low. Eat well, make sure you're getting enough calories, and that you get more from complex carbs, protein, and fat sources than sugar, and seek a suitably qualified individual to look at your training needs.
Hi everyone here I can tell you some healthy ways that helps you to gain fat are; Add chicken and fish in your diet. Drink shakes and smoothies. Exercise regularly. Eat foods that are high in nutrients. Eat some junk foods to get more fat.
