If you are overweight then you need to trim down the excess fat but at the same time also need to work out in such a manner that you get muscle fast.
The same applies if you are skinny and want to build up quality muscle instead of bulking up on fat.
Embark on a mission to burn fat.
If you are overweight then in addition to weight training, you will also need to embark on exercises such as aerobics, swimming, jogging or even walking as these will quickly burn away excess fat while building up endurance levels.
While you build up vital muscle mass with weight training on one hand, you will end up losing the extra baggage of fat on the other.
Change your diet.
Your diet would most probably have been the culprit in raising your fat levels in the first place anyway.
You will now need a diet that is rich in proteins and carbohydrates but containing minimum levels of fats.
This too will help you to quickly trim down fat levels.
If you are skinny then you will have to increase your calorie intake, albeit in a healthy way so as to bulk up on muscles.
Keep an eye on your body weight and fitness levels.
As you get into your new fitness regimen, you will need to constantly monitor your fat levels along with your weight and muscle gain.
This is very important since you will need to change your diet and exercise routines as you start getting fitter and replace fat with muscle.
Your new diet will then need to ensure that your muscle levels are maintained even while you do not deviate from your ideal body weight.
Take one step at a time.
Instead of shocking your body by exercising too much while also cutting down on your diet drastically, make sure that you take it one small step at a time.
Give your body some time to adjust before increasing your exercises or cutting down further on your calorie input.
This progressive move will ensure that you safely convert your fat into ripped muscles without facing any problem.