There are three basic human body types: the ectomorph, the mesomorph, and the endomorph.
Despite what it might feel like at times, you are not completely bound to one category or the other
Your lifestyle, genetics, history and training style all play a part on how you look, and you can definitely change it overtime.
ECTOMORPH: An ectomorph tends to be thin, and struggles to gain weight as either body fat or muscle.
They can eat piles of food and stay looking the same even when gaining muscular weight is their biggest goal.
People who battle to gain muscle are often known as "hard gainers"
Ectomorph tends to have a lean build, long limbs and small muscle bellies. Even if an ectomorph manages to put on weight, they may still look Skinner than they are particularly in the calves and forearms.
MESOMORPH: The mesomorph has a middle-of-the-road that takes the best of both worlds. They tend to have a wild shoulders, a narrow waist, relatively thin joints, and a round muscular bellies.
In short if you are mesomorph you have a natural tendency to be fit & relatively muscular.
ENDOMORPH: The endomorph tends to gain weight and keep it on
Their build is a little Wider than ectomorph and mesomorph with a thick rib cage, wide hips and shorter limbs
They may have more muscle than either of the other body types, but they often struggle to gain it without significant amount of accompanying body fat.
If you ever feel you gain 5 pounds simply by walking by a donut shop, you may be an endomorph.