While it's true that you can't out-exercise a bad diet, if you're just starting out and have a lot of fat to lose, it may be best to leave your diet as-is and start with exercise.
The reason I recommend this is because I find that people tend to drastically cut calories thinking it will help. But in reality, cutting calories messes with your metabolism and affects your body's ability to adapt and recover. Also, remember, we're playing the long-game with the end goal being healthy fat-loss (and not just weight-loss).
It's much better to get your fitness up and THEN tweak your diet. It'll be easier then too - when you start exercising, you'll naturally want to reach for healthier foods (thanks to an enzyme called peptide YY).
Don't get me wrong, replacing un-healthy foods with healthy foods is excellent at any time and a great way to begin making sustainable changes to your diet. But the bottom line is that cutting calories drastically at the beginning is a no-no, if what you're after is safe and sustainable fat loss.
Poul Nielsen is the owner and operator of Nielsen Fitness, Toronto's leading team of in-home personal trainers. He has 18 years' experience in the fitness industry and has taught courses in Fitness and Lifestyle Management at George Brown College.
In addition to exercise (obviously), he loves spending time with his family, playing the guitar, strong coffee - and dark chocolate!