This is a really simple concept to understand if you know how your body works.
Muscle EATS Fat.
The more you work on building lean muscle in your body, the more fat you will burn.
That means while working out and doing all the other things in life you do.
Everything you do takes energy. You walk, talk, blink your eyes, think, breath, your heart beats constantly....are you following me on this?
Your body is CONSTANTLY burning calories as energy for EVERYTHING you do. Yes even sleeping takes energy.
Now.... the more muscle mass you have on your body, the more food your muscles need.
And what do muscles eat? MUSCLES EAT FAT.
So if you have more muscle, you will burn more fat.
In addition to that, going to the gym and doing resistance training (lifting weights) will burn calories and help you to lose fat and stay slim.
So the bottom line is...
If you want to win the war against fat, get started with an exercise program where the main focus is building lean muscle.
When you do this, you will not have to worry about losing fat. The new lean muscle mass you build will take care of this for you.
The fat is the food your newly acquired muscles will feed on.