Proper diet and exercise can help speed up a person's metabolism -- the rate in which the body burns calories -- nutrition and fitness experts say.

"Metabolism is fairly stable, but there are things that we can do to rev it up," says registered dietician Pamela Downer.

The first step to mastering one's metabolism is mastering meal times, beginning with breakfast.

"When you eat breakfast, you end up eating less throughout the day," Downer says.

Studies show three light meals placed about four hours -- with light snacks in between -- are the best way to boost metabolism.

The best metabolic meals follow the fuel formula: 30 percent protein, 30 percent good fats and 40 percent carbohydrates.

Paired with regular workouts, "Most people can really influence their metabolism," sports physiologist Rob Herzog says.

Herzog recommends cardiovascular exercise and weigh training to help boost metabolism. Lean muscle and changing workouts keep the body burning calories.

Metabolism is determined by a number of factors, including genetics. Women naturally have slower metabolisms than men; and for both sexes, the ability to burn calories wanes as they get older.

Some research suggests that not getting enough sleep can disturb normal metabolism