Bodyweight exercises are an effective tool to build strength and lower body fat.
It can be done anytime, anywhere and without any fancy equipment - which makes it a great time saving way to build strength and fitness.
Here are a few examples:
1) Reverse Crunch - knees bent, hands placed beside your hips flat on the floor, bring your knees towards your chin while exhaling. Your hips should come off the floor and slowly lower your feet to just above floor level. Do 15-20 reps.
2) Side (Plank) Bridge - lie on your side so that your body is rigid and straight. The only contact points on the floor are your forearm and the near side of your foot. Do 20-30 seconds.
3) Front Bridge - Lie face down so that your body is rigid and straight, the only contact points on the floor are both forearms and both sets of toes. Do 20-30 seconds.
4) Split Jump - Stand in a lunge position with one leg between half to a meter in front of the other, arms at your sides. Bend at the knees until your back leg almost touches the floor, then swing your arms forward and jump as high as you can. While in the air, switch leg positions so that you can land softly with the other leg in front. Repeat for 8 to 12 reps.
5) Push-ups; or if you are a beginner try the kneeling push-up (push up position but with your knees on the floor)
Bodyweight exercises can be adjusted as the fitness level improves.
As your strength improves, adjust the exercises to make it more challenging. For example, you can change the kneeling push-up to the same push-up from your toes. Or if you want to make it more difficult, why not adjust the position of your hands to continuously advance your muscle strength. Other ways to make it more challenging are to increase the intensity like varying the repetitions, sets and shorten the rest period between each sets. Best yet, 10 push-ups followed immediately by 10 split jumps. Then rest for 60 seconds, and repeat again. The aim here is to increase the intensity by alternating between an upper and a lower body exercises for greater impact.