In fact, your request is not to increase fat, but to increase the density of thin skeletal muscle. The effect is that people look strong, not fat. Really fat, losing weight is also a hassle.
The method of gaining weight is simple. The nutrient of skeletal muscle is "protein". Eat more food and water containing protein. Note that it is water, not carbohydrates. If you eat more carbohydrates, you will get fat.
Don't think it's ugly for girls to gain muscle. In fact, girls are fatter than boys.
As long as you increase muscle density, as long as you don't practice bodybuilding, you will definitely not see muscle protrusions and your skin will feel tighter.
In addition, the density of skeletal muscle will only increase on long bones, which is where there are bones. On the other hand, Bobo itself is loose connective tissue. As long as it is not excessive exercise, it will not become a muscle.
The protein content in food is the most abundant in "soybean", followed by "fish" and "chicken". Don't eat beef and mutton, it's easy to get fat.