You have to be exercising pretty vigorously to work off everything you're eating, or else, not eating enough. Of course, if you do that, you would lose weight, but you aren't leaving any nourishment for your primary body functions, such as heart, brain, kidneys, liver digestion, etc. Eventually, your health would suffer.
Depends on what you eat. High insulin prevents fat burning. I know since I've had insulin resistance for years. No amount of exercise, calorie intake, or a year of hyperthyroidism did anything for weight loss. But I cut out the refined sugar and hello weight loss with no exercise. :)