The three different body types are Endomorph, Mesomorph and Ectomorph. What is your body type? and depending on what body type you are will you need to train differently or be on some kind of special diet?
This is the naturally thin body type, they have a thin bone structure, less muscle mass and they may find it hard to gain weight. They may have a faster than usual metabolism which burns calories quicker than normal. Recommended workout style to gain weight would be weight training with lots of compound exercises to build those larger muscle groups. Compound exercises are always the best exercises to start with, but with Ectomorphs it makes it especially true. Their diets should be higher in calories to support their weight gain, ideally these calories should come from healthy foods, supplements could be a nice way of boasting calorie and nutrient intake.
This is the largest of the body types, broader skeleton and overall a stockier build, they may find putting on body fat and muscle mass easier. Endomorphs could possibly have a slower metabolism than the other body types however this is not always the case. They may find it easy to put on weight but find it difficult to lose weight. Including cardio training combined with weight training would be a good idea to burn some extra calories. Endomorphs with slower metabolisms may need to be more careful with their calorie intake.
This is the body type that falls into the middle of the other two, they have a broader skeleton than Ectomorphs but not as broad as Endomorphs. Mesomorphs are usually athletic, or they have the potential to develop athletic builds with good tone and definition, they can usually build muscle quickly, however they can also gain body fat if they consume to many calories. Weight training workouts will normally get good results plus include some cardio to help keep that body fat percent low.
Some people are not necessary just restricted to one body type, they can be a combination of two of these body types. No matter what body type you are you can still achieve a great deal with the right training and a good balanced healthy diet.
There have been recent studies that suggest that our metabolisms only differ slightly, so if you are an Endomorph body type your metabolism may only be slightly slower than that of the other two body types, and perhaps not slower at all. So if you are an Endomorph and you are overweight, your Endomorph body type or your genetics may not be to blame.