It could be that you're overweight and think you need to lose a few pounds before you start working out. So, you've decided that you're going to lose weight by dieting BEFORE you start an exercise program. You've even got a list of groceries to restock your fridge and pantry with and to start you on your way.
It's true that watching what you eat is a huge part of a fitter, trimmer life. But studies show that making the switch to healthier eating is easier when you're already working out regularly.
Exercise will cause you to crave healthier foods, encouraging a fit diet to come more naturally, and the pounds to melt off quicker!