One in three Americans is overweight and another third are obese, according to the Centers for Disease Control and Prevention. But while carrying too many extra pounds can increase your risk for heart disease, diabetes, and some cancers, health experts say a little bit of flab may actually be healthy.

But there is a kind of “Goldilocks Effect” — not too much, not too little — when it comes to body fat.

“Researchers have concluded that fat is actually a vital organ that releases hormones and sends special signals to the brain,” notes Dr. Holly Lucille, ND, RN. “Fat is an important macro nutrient and like any other macro nutrient, the quality makes a difference. Having the right kind of fat on your body is both protective and important.”

Jeffrey Friedman, a molecular biologist at Rockefeller University was among the first scientists back in the 1980s to discover that there was more to fat than merely storing calories. In his experiments with mice, he found that fat produces a hormone called leptin which is released into the bloodstream and binds with the areas in our brain that are responsible for appetite.

His lab’s obese mice had a genetic defect in their fat that prevented the manufacture of leptin which gave them the signal to stop eating. Humans with the same genetic defect can eventually eat themselves into obesity and premature death.

So, losing weight becomes a double-edged sword. When we lose fat, we lower our levels levels of leptin, the appetite off switch, and we become hungrier than before.

Leptin also affects our muscles and thyroid hormones so that lower levels of leptin slow down our metabolism. This combined effect drives us to regain weight. It may also explain why extreme dieters who lose vast amounts of weight in short periods of time nearly always gain it all back — and then some, scientists say.

Scientists also know that fat affects the size of our brains. People who are genetically leptin-deficient have smaller brain volume in some areas as do patients who are suffering from eating disorders such as anorexia which leave them malnourished. Leptin is also helpful in healing wounds and strengthens our immune system by activating T-cells.

“What’s important is the quantity and quality of your stored fat,” Lucille tells Newsmax Health. “The ‘good’ type of fat is called subcutaneous and is found directly under our skin in places such as our abdomen thighs, buttocks, and arms.”

Subcutaneous fat is easy to grab with your hand and tends to shift as the body changes position.

The so-called “bad” type of fat is visceral fat which is stored under the stomach wall, nestled against our internal organs. This type of fat can become inflamed and lead to diabetes and heart disease. It tends to be firmer and dense.

But experts warn that excess body fat of either kind is unlikely to be health-promoting. It’s important to keep fat levels at their optimal levels which can vary according to age and sex.

In general, women with more than 30 percent body fat are considered to be overweight and for men, the threshold is more than 25 percent.

Dr. Cate Shanahan, author of “Deep Nutrition: Why Your Genes Need Traditional Food,” tells Newsmax Health that women, especially need a body composition of at least 10-12 percent fat in order to produce enough estrogen to cycle regularly and to maintain normal libido.

And as we age, a little more fat can enhance our looks.

“As we age we lose that facial body fat and our hormones simultaneously fall,’ she says. “Body fat helps support normal estrogen levels and therefore contributes to normal bone density — a critical factor in healthy aging after the age of 65.

“But that minimum percentage must be subcutaneous fat. When the visceral fat reaches more than 2 percent of our body composition it can lead to poor insulin sensitivity and potentially the beginnings of diabetes.”

The good news is that the “good” fat can fight the “bad” fat. By making a substance called adiponectin, subcutaneous fat helps take circulating fats out of your veins and into the subcutaneous tissues where they belong.

This hormone also reduces visceral fat. Exercise helps release adiponectin which is why sumo wrestlers can be both fat and fit. They exercise seven hours daily which keeps their visceral fat under control.

Experts say we should embrace the new science of fat, and Shanahan quotes an old French proverb that praises fat more poetically: “After a certain age a woman must choose between guarding her figure at the price of a hollow face.”

“I think the take away message of the new research is that we must keep a healthy level of fat to reduce our risk of disease while maintaining optimal body function,” notes Shanahan. “But don’t rationalize and run with the theory that eating bad fats are good for your health. You still need to choose your fats wisely and keep them within healthy levels.”