During the holiday season, many of us tend to pack on extra fat. However, research has discovered that not all body fat is equal. In fact, some types of fat are beneficial. Here, I describe three types of fat – white, brown and beige – and explain their effects on the body.
White fat accounts for the vast majority of our bodies’ fat and, unfortunately, is the type we’re likely to add during the holidays. White fat can be subcutaneous (the squishy stuff under your skin) or visceral (located around your internal organs). While an excess of either type is detrimental, studies suggest that visceral fat is more harmful for metabolic health and increases an individual’s risk for insulin resistance (1, 2). In the past, it’s been thought that white fat is an inert tissue, which simply acts as a storage depot for energy reserves. Now, we understand that white fat releases hormones, including leptin and adiponectin, that can shift a person’s metabolism to decrease satiety, thereby promoting overeating and increasing storage of additional white fat. Additionally, white fat releases other pro-inflammatory signaling molecules called Adipokines, which increase systemic inflammation, heightening the risk of developing diseases associated with obesity, such as heart disease. Together, these factors can drive a vicious cycle of continually increasing obesity and inflammation.
The effects of brown fat, a type of fat found on the upper chest and neck, are more advantageous. Brown fat is loaded with mitochondria (the “powerhouses” of the cell). The mitochondria in brown fat are particularly poor at converting stored energy into a usable form (ATP), due to their high content of uncoupling proteins. In short, brown fat does little more than burn energy to create heat. This is why brown adipose stores are greatest in hibernating mammals. In contrast to white fat, brown fat has beneficial impacts metabolic health including improved glucose metabolism. Unlike white fat, brown fat is derived from a muscle cell lineage. It is actually brown in color and has a similar appearance to muscle tissue.
The newest trend in fat research is around beige fat. Unlike brown fat, beige fat is not derived from a muscle cell lineage. Rather, it is derived from an adipose cell lineage, as is white fat. Yet, from a metabolic standpoint beige fat is much more similar to brown fat because it is metabolically inefficient and burns excess energy as heat. Like brown fat, beige fat has beneficial impacts on metabolic health. We are only beginning to understand how white adipose tissue is converted into beige fat.
Body fat is no longer simply thought of as an energy storage depot. Our more nuanced view shows there are several types of body fat that can have either beneficial or detrimental impacts on health. There is a great effort underway to understand how we can use the advantageous effects of brown fat and beige fat to fight obesity and improve human health. The good news for this time of year is that some evidence suggests exposure to cold temperatures can increase brown fat stores. Perhaps the best advice is to move around outside, embrace the cold, and try to avoid extra trips to the dessert platter.