Most people carry both white and brown fat. During obesity development, excess calories are mainly stored in white fat. In contrast, brown fat burns energy and thereby generates heat. More than 90% of the body fat deposits in humans are white and are typically in the abdomen, bottom and upper thighs. Converting white into brown fat could be a new therapeutic option to combat weight gain and obesity, the university stated in a press release.
The researchers, led by Florian Kiefer, demonstrated the “moderate application of cold increases the levels of vitamin A and its blood transporter, retinol-binding protein, in humans and mice. Most of the vitamin A reserves are stored in the liver and cold exposure seems to stimulate the redistribution of vitamin A towards the adipose tissue. The cold-induced increase in vitamin A led to a conversion of white fat into brown fat (“browning”), with a higher rate of fat burning.”
Brown fat is turned on, or activated, when you get cold, according to the Mayo Clinic. Brown fat produces heat to help maintain your body temperature in cold conditions. Brown fat contains many more mitochondria than does white fat. These mitochondria are the “engines” in brown fat that burn calories to produce heat.
“Our results show that vitamin A plays an important role in the function of adipose tissue and affects global energy metabolism. However, this is not an argument for consuming large amounts of vitamin A supplements if not prescribed, because it is critical that vitamin A is transported to the right cells at the right time,” Kiefer said. “We have discovered a new mechanism by which vitamin A regulates lipid combustion and heat generation in cold conditions. This could help us to develop new therapeutic interventions that exploit this specific mechanism.”
Most dietary provitamin A comes from leafy green vegetables, orange and yellow vegetables, tomato products, fruits, and some vegetable oils, according to the National Institutes of Health. The top food sources of vitamin A in the U.S. diet include dairy products, liver, fish and fortified cereals; the top sources of provitamin A include carrots, broccoli, cantaloupe, and squash.