Dieters often concentrate on calorie counting. That's wise, given that the basic equation of weight loss will always remain true: more calories consumed than used leads to weight gain. But that statement makes it sound as if a calorie is something you eat and if you ate fewer you would lose weight. That is not quite accurate.

In simplest terms, a calorie is a measure of energy. In science, the unit that measures it is the calorie, cal. But because the amount in food is typically so large, the food calorie is actually a thousand of those or kcal (kilocalories). Food calories are sometimes denoted with a capital C to make the difference clear.

But whatever name they're given, the basic point is that a calorie represents a certain amount of energy, not a quantity of mass or weight. So, how does that make you gain or, hopefully, lose weight? The explanation revolves around what the body does with that energy.

When food is consumed it's digested. That much is common knowledge. What happens next is not so well known sometimes.

Part of that digestion process involves breaking down foodstuffs containing, say carbohydrates, into smaller parts. The process yields energy that the body can use to power muscle movement, cell repair and a million other vital aspects of human biological function.

Note that little phrase 'can use', though. What happens when there is more energy available than the body needs immediately for all those functions? It doesn't shed (all of) the rest. It stores (some of) it. Like a battery that is ready to provide energy when a tiny motor needs it, excess energy is stored in chemical bonds. When the energy is needed later those chemical bonds are broken and the energy is released.

But chemical bonds are bonds between two or more things. In this case they are primarily the bonds between molecules in fat cells, also known as adipose tissue.

Typically, glucose in the blood stream provides all the energy the body needs. When there is a deficit the liver is stimulated to provide more. But if that process continues, the body will go after that energy stored in fat cells in a process known as ketosis.

That is, in simple terms, how body fat is reduced. Create a large enough 'energy deficit' for long enough and the body will make available the energy stored in fat by breaking down those fat molecules. The net result is less fat stored and a lower body fat percentage overall.

That's the goal of most dieters whether they realize it or not. The idea isn't simply to lose weight, per se. After all, the number on the scale isn't that important in most cases. Building up muscle, for example, actually increases weight because it is relatively more dense. What is important is the distribution of that weight - whether too much of it is in the form of stored fat, and where that body fat is stored.

If you wonder why it can be so hard to shift that balance, one simple number tells much of the story. A single pound of body fat is equivalent to 3,500 calories. That means you have to burn 3,500 calories to convert one pound of fat. That explains why a diet needs to be a long-term commitment. Burning that many more calories than you consume simply takes time.

So, reduce the number of calories taken in and the body will store less in the form of fat. Reduce them enough and it will burn the fat that is there to provide energy for life. The consequences to the dieter are a more attractive figure, ample energy for all of life's goals and better overall health.