Can brown fat tissue be targeted for fat burning? Current findings on this topic were presented at the 67th German Congress of Endocrinology. Some statistics highlighted the need. Approximately 53% of the German population (almost 47% of women and 60% of men) are overweight (including obesity). Obesity is present in 19% of adults. The condition not only results in a shorter life expectancy but also increases the risk for cancer, diabetes, and cardiovascular diseases.
“The current treatment focuses on reducing energy intake, for example, through GLP-1 [glucagon-like peptide 1] agonists, which induce a feeling of satiety and significantly reduce body weight,” explained PD Tim Hollstein, MD, of the Institute of Diabetes and Clinical Metabolic Research at the University Hospital Schleswig-Holstein in Kiel, Germany. But the effect of weight loss injections only lasts for the duration of their application, and they are expensive.
“A potentially more sustainable treatment option would be to increase energy expenditure,” said Dr. Hollstein. He explained the role of brown fat tissue at a press conference for the German Society of Endocrinology (DGE) Congress.
“Brown fat tissue is like a heater for our body and kicks in when we are cold,” said Dr. Hollstein.
Brown fat tissue is primarily found in babies who cannot generate heat through muscle shivering. It has only been known for about 15 years that adults also possess brown fat. PET scans have shown that women generally have a higher amount of BAT and a higher energy intake capacity. The chance of discovering brown fat tissue was lower in older patients (P < .001), at higher outside temperatures (P = .02), in older patients with higher body mass index (P = .007), and if the patients were taking beta-blockers (P < .001).
Two Metabolic Types
An average person has about 100-300 g of brown fat tissue, mainly around the neck and collarbone and along the spine. Interestingly, just 50 g of active BAT can burn up to 300 kcal/d. “That’s roughly equivalent to a chocolate brownie,” said Dr. Hollstein. Lean individuals have more active BAT than overweight people, suggesting that BAT plays a role in our body weight.
In addition to its “heating function,” BAT also produces hormones, so-called “batokines,” which influence metabolism and organs such as the heart and liver. An example of a batokine is the hormone fibroblast growth factor 21, which promotes fat burning in the liver and can protect against fatty liver.
Recent studies have shown that BAT is activated not only by cold but also by food intake. BAT thus contributes to so-called “diet-induced thermogenesis,” which is the energy the body needs for digestion. Some people have a higher digestive energy than others, despite having the same food intake. They burn excess calories and can thus protect themselves from being overweight.
“There are people who have a more wasteful metabolism and people who have a more economical metabolic type, meaning they have less brown fat,” explained Dr. Hollstein. Interestingly, BAT also seems to induce a feeling of satiety in the brain, which could be significant for regulating food intake.