The theory of Somatotypes classifies human bodies according to three general types: thin and lanky ectomorphs, naturally muscular and athletic mesomorphs and bulky, but soft looking endomorphs. The Somatotype theory holds that adjusting nutrition and diet to each specific body type will help individuals achieve their dietary goals. While mesomorphs possess a genetic advantage in their ability to gain muscle and burn fat easily, type-specific nutritional recommendations will help them further maximize lean muscle gains and weight loss.
While mesomorphs possess advantages the other body types lack, they cannot take their genetic advantages entirely for granted. Furthermore, a poor diet can lead to health risks and nutrition-associated diseases, and aging will eventually erode the robust metabolism of a mesomorph.
A mesomorph can determine how many calories she needs to eat per day to maintain her current body weight by multiplying her current body weight by 15 (therefore, a 200 lb. person needs 3,000 calories daily). On a macronutrient basis, mesomorphs should strive to eat a diet that is 40 percent carbohydrate (carbs), 30 percent protein, and 30 percent fat.
Diet to Gain Lean Muscle Mass
Mesomorphs looking to gain weight, especially in the form of lean muscle mass, must take in more calories each day than their body needs to simply maintain their current body weight. Mesomorphs looking to lose weight can take in slightly fewer than their maintenance calories, while making adjustments to the types of food they eat and their training. Also, mesomorphs looking to gain lean muscle mass must take care to eat more calories and a higher amount of protein, even on days that they do not exercise.
To gain lean muscle mass, mesomorphs should shoot to increase the amount of protein they take in. Aim for 1 to 1.5 g per pound of body weight. Additionally, lower the total amount of carbohydrates you ingest, and try to eat more low-glycemic index carbs (potatoes, whole grain breads, pastas, bagels). Eating more of these slow-digesting carbs will help keep insulin levels steady so that more of the weight you gain will be in the form of lean muscle, rather than stored fat. The only time a mesomorph should eat high-glycemic (fast-digesting) carbohydrates (like maltodextrin or glucose) is with their protein after a workout.
Diet to Lose Fat
Mesomorphs looking to lose weight should strive to eat smaller meals more frequently. This will cause a feeling of satiation (fullness) that will help them eat less, and will also help keep insulin levels steadier. By contrast, eating big meals at infrequent intervals, will cause insulin spikes that cause your body to store calories as fat.
Also, when you do eat carbs, eat them only at specific meals, directly after training (post-workout) and at breakfast. At the remaining meals, substitute green vegetables and fruits instead of carbohydrates, and focus on high-fiber items that will further increase satiation. If trying to lose weight, try to only eat low-glycemic carbs; this will aid muscle gain and fat loss.
For fat content, shoot for foods rich in omega fatty acids (3, 6 and 9), like salmon, and take in good fats that include essential fatty acids. These include, nuts, avocados flaxseed and olive oils. Even when trying to lose weight, your body still needs enough fat, particularly to make testosterone, which will not only help build muscle but burn fat as well.