Body fat has gotten a bad rap in recent years. It’s understandable given that 70 percent of American adults are reportedly overweight or obese, costing $190 billion per year in related medical bills. But new research shows not all fat is created equal.
Washington State University professor of animal sciences Min Du says our bodies are equipped with both good and bad types of fat that naturally work together to balance weight and metabolism. The process—along with a little help from diet and exercise— involves an intricate interplay between white, beige, and brown fat—or adipose tissue.
“When most people think of body fat, they’re thinking of the ‘bad’ white fat,” says fellow researcher Eva Szentirmai, an associate professor in the Elson S. Floyd College of Medicine at WSU Spokane. Although protective in healthy amounts, “white fat stores the extra calories we eat in a form of fat that makes people obese,” she says. “It also increases chances of metabolic disorders.”
Du says overeating allows white fat cells to enlarge to the saturation point. As the overloaded cells age and die, they release molecules called cytokines that cause inflammation leading to problems like insulin resistance and type 2 diabetes.
Nature provided a feedback loop meant to prevent such inflammation, says Szentirmai. As white fat accumulates, it secretes a hormone called leptin that decreases the urge to eat. But those with obesity can also become resistant to leptin and no longer respond to the hormone’s appetite suppressing effects.
Until recently, scientists believed adults were at the mercy of this “bad” fat and had little of the “good,” heat-generating brown fat typically found in infants. In 2009, several independent studies revealed that adults actually have quite a bit of brown fat. Not long after, it was discovered they also have “good” beige fat.
Szentirmai says brown fat is good because it actively signals white fat to release stored lipids which are then burned as heat. “Brown fat burns calories and can help decrease weight. It has also been shown to increase insulin sensitivity thereby lowering blood glucose levels and decreasing the incidence of metabolic disorders.”
Brown adipose tissue owes its power to the many mitochondria—tiny energy plants—that pack its cells. Beige fat, a cross between white and brown fat, also has mitochondria and the numbers increase as it becomes more active.
Du says beige fat forms as small islands of cells within white fat in a process called “browning.” This conversion from white to beige fat is initiated by things like antioxidants in food, exercise, cold, and certain anti-diabetic drugs.
He recently demonstrated that resveratrol, a polyphenol antioxidant found in red wine, berries, grapes, and other fruit, can enhance the conversion. In the study, mice on a high-fat diet gained 40 percent less weight than controls when supplemented with resveratrol in amounts equal to 12 ounces of fruit per day for humans.
“Whole fruit contains a range of polyphenols that increase gene expression and enhance the oxidation of dietary fats so the body won’t be overloaded,” he says. Curcumin and the capsaicin in hot peppers also activate good fat as does exposure to cold temperatures.
Du says physical exercise helps keep you trim by triggering fat conversion through irisin, a newly discovered hormone in skeletal muscle.
Fat also plays a role in sleep quality. Szentirmai, who studies the interaction between sleep and fat, says brown fat not only burns calories, it also promotes normal sleep patterns in mice. Obesity, with it’s preponderance of white fat, is often associated with sleep loss.
Together, these findings offer intriguing new avenues for future treatment and prevention of obesity, For now, Du recommends exercise and a diet rich in fruits and vegetables…along with a caveat: You have to keep at it or that beige fat will convert right back into white.