Resistance, or weight training is a crucial component of any weight loss program.
Despite what most people think, cardio alone will not help you in your efforts to lose weight.
Resistance training helps build lean muscle, and the more lean muscle you have the more fat you will burn.
Think of it as turning your body into a fat burning "furnace".
Lean muscle burns more fuel - from food, so when you eat the calories in your food are burned up and not as much is stored as fat.
This in turn will help speed up your metabolism, thus making your body burn more energy instead of storing it as fat.
Children and people with high levels of fitness have high a metabolism.
You will often see some kids (or even yourself when you were a child) eat a lot of unhealthy foods and not put on any weight, this is because their metabolism if higher.
This diminishes with age and so often you will see someone who was skinny as a child is now overweight in adulthood.
For good results you should do your resistance training at least 3 days per week, 48 hours apart and each session should be no longer than 60 minutes.
Train both the upper and lower body, on separate days.
Upper body: chest, back, shoulders, biceps & triceps.
Lower body: quads, hamstrings, calves and abs.
An example of this could be Monday: Upper Body; Wednesday: Lower body; Friday: Upper body.
Reverse this the following week.