The best way is to work your ass off, burn way more calories than you eat, but you have to keep eating healthily or else your body will go into starvation mode and will hold ON to its precious calories. You’ll also lose some water weight during the first few days if you go from completely inactive to moderately active.
Colonics don’t work, period (your colon doesn’t need help cleaning itself, and you don’t have pounds of impacted stuff up there despite what the sellers of colonics would have you believe). Anorexia doesn’t work, your body goes into starvation/protection mode and all sorts of weird things start happening, but more importantly it won’t get rid of fat at all. You could also get it cut out of you, but the healing time would be longer than three weeks and you’ll just put it right back on eventually. There is no solution beyond working it off of you, and that’s done through nutrition and exercise. There is no secret pill, nothing.