Cells in the human body turn fuel into a form of energy that can be used by the body for maintenance, internal processes, growth, repair etc.   An imbalance between kilojoules consumed (food or fuel) and kilojoules expended will lead to weight gain.

Losing weight is the product of a simple chemistry equation. Burn more kilojoules than you consume. Sounds simple, right? But, as you may know, in the real world it can be much more complicated and frustrating. Every day we see new ways of burning kilojoules quickly with less effort. Concoctions, pills, and special exercises designed to "boost" your metabolism, offer the promise of easy weight loss at every turn.

Here's the real truth:  Physical activity is the only real way to increase kilojoule burn!

The first (and most obvious) benefit of physical activity is that you burn kilojoules while you do it. Physical activity throughout the day, plus exercise, goes a long way toward achieving a kilojoule balance -- burning more than you eat.