You might think all body fat is created equal, but there is more to the story. Where fat is stored impacts health.

Subcutaneous and visceral are the two storage forms of fat. The fat hanging under your arm or inside your thighs is subcutaneous -- literally ``under the skin.'' Most people don't like seeing it, but it's not a specific health threat.

However, visceral fat -- that familiar beer belly or ``muffin top'' -- lies beneath the muscle, surrounds vital organs and is metabolized by the liver into cholesterol. Visceral fat is a risk for heart disease, diabetes and metabolic syndrome. Heredity, a diet high in saturated fat and a lack of physical activity all contribute to its development.

An article last month in the journal Obesity addressed the interesting question of what happens to visceral fat when you lose or gain weight. The study followed 208 overweight women between ages 21 and 46 who were put on a medically supervised, very low-calorie diet.

The women were assigned to aerobic exercise, resistance exercise or no exercise. Their average weight loss was 26 pounds. Their total body fat was measured, and they were advised to continue the same exercise (or non-exercise) regimen along with a healthy diet.

At the one year follow-up, their weight and body fat were remeasured. The women who kept exercising, although at a lower intensity, regained about 7 pounds, while the non-exercisers put back about 14 pounds.

Those who did not exercise also had a 33 percent increase in visceral fat. The good news is that even with weight gain, the women who continued with 80 minutes of exercise a week did not regain visceral fat.

The take-home lesson: A healthy diet gets you on track, but you need to exercise to keep your body running smoothly.

Sheah Rarback is a registered dietitian and on the faculty of the University of Miami Leonard M. Miller School of Medicine. Her column runs every other week.