This is not technically a measurement, but it is a number which, if you pay attention to it, can have a huge influence on your health. You can work out your daily calorie needs by multiplying the number of kilograms you weigh by about 28 to 33 (or pounds by 13 to 15), depending on your activity level.

In a perfect world, you'd eat just enough to provide fuel for your body. If you were trying to lose weight, you'd eat roughly 500 calories less than your body needs. In reality, many of us eat between 100 and 1,000 calories more than we need, every day.

For your health's sake it is vital to discover and understand your daily food needs and whether you're exceeding them. The obvious reason is that overeating leads to weight gain, and overeating is one of the worst things you can do for your heart. The slightly less obvious reason is that eating too many calories usually means eating unhealthy foods, which are much higher in calories than natural foods because they usually contain a lot of fat or sugar—or both.

Most women need 2,000 calories a day for good health. Men generally need about 2,550. That roughly equates to 300 to 400 calories for breakfast, 500 to 600 for lunch, 600 to 700 for dinner, and two or three snacks of roughly 100 to 200 calories each.

But your daily calorie need isn't a static number; it can change over time. If you are exercising more, recovering from illness or injury, or going through a period of high stress, your body may need extra fuel. If you've lost weight, the chances are your body requires less fuel than it once did. Then there's metabolism—some of us burn calories more efficiently than others.

The important message is that all adults should be aware of how much food they need to eat each day for optimal health, energy and weight.