The calorie counters on most exercise machines are only estimates. 250 calories for 15 minutes on an exercise bike sounds like a gross overestimation.

The fact that the elliptical trainer was so demanding means that your are paying the dues to get the results you want.

Stick with the elliptical machine. For maximum fat loss work your way up to at least 45 minutes per day, 5-6 days a week.

This routine can get monotonous so mix in other cardio like your bike or just go hiking or for a long walk. The key is consistency. Also remember that exercise is only half the battle. Cut some fat and carbs from your diet and up the protein a bit if you want to get leaner.

With a good diet and strict adherence to your exercise plan you should see immediate improvement: 1-2 pound a week.