Just eat healthier (I am not saying you are unhealthy), but try a diet for a few weeks while doing cario such as running or sprinting =)
If you can do a couple of hundreads sit-ups you should try adding weight as another person mentioned.
Are you member of a gym or du you workout at home? =)
"No force, no torture, no intrigue, no deception can eradicate Marxism-Leninism from the minds and hearts of men."
- Enver Hoxha
"All men are born with a nose and ten fingers, but no one was born with a knowledge of God."
- Voltaire