Exercise is ideal, but most people* don't burn enough calories exercising to enter a calorie deficit. Worse still: appetite spikes after exercise make most people eat more. All that really matters is eating below your maintenance calories. Exercise is the cherry on top for making your body actually look good.

*If you're weightlifting HEAVY 2-3 hours a day 6 days a week or running marathons every weekend, then you are burning enough calories to enter a deficit. Otherwise: your workout is burning fewer calories than there are in a banana.