It is true that some people born with great physique and naturally athletic, or some people build the great physique and become athletic through their pure hard work as they grow up.
If you think you are athletic and have a tendency of gaining muscle easily, it is highly likely that you have characteristics of mesomorph, so instead of spending time on running machine and other cardio exercises, regular weight training with proper diet is recommended to lose weight.
In order to increase muscle definitions, you need to do exercises that can grow traps, triceps, biceps, and deltoid etc. Just by losing body fat will not turn your body into muscular.
Therefore, it is best for mesomorphs to do regular weight training program for losing fat and obtaining muscular physique.
Secondly, diet plan is very important. People say we need to lower the level of body fat while we keep the muscle mass to the same level or increase them but this is not that easy as it sounds. In order to lower the body fat, it is essential to avoid carbohydrate which is the very first source of energy of the body, meaning too much unnecessary intake of carbohydrate will be wasted and stored as fat. Therefore less intake of carbohydrate and more intake of protein will help to lose fat, and increase the muscle mass.
If you haven’t exercised for a long period of time, it is best to start with jumping rope, and push up. These exercises are great way to lose fat, and build muscles at the same time easily. If you have characteristic of mesomorph, you will see the result pretty fast on growing muscles. Having enough rest and proper exercise routine with a proper diet, will get you a ripped body as long as you would be consistent.