The fight against obesity. A team of Danish and German researchers reports a new discovery

A cure for obesity may have been in our body fat all along. Scientists have discovered a genetic “switch” for the brown fat in the body that helps us burn calories. By knowing why brown fat stops burning calories, researchers can now find a way to activate it on command, which could help overweight people lose excess weight.

Unlike white body fat, brown fat is considered healthy because it helps us burn calories. As a result, research interest in brown fat is significant, and now a team of Danish and German researchers is reporting a new discovery.

For years, newborns have been known to have brown fat, which helps them regulate their heat. However, about 15 years ago, researchers discovered that brown fat also exists in adults.

Since then, scientists have been trying to learn more about brown fat because it has a unique ability to burn calories—even if you’re sitting on the couch instead of working out at the gym. However, calorie burning only occurs when brown fat is active, which is rare in adults.

A big question arose: How can brown fat be increased and activated? And can this activation lead to a calorie burn so significant that it helps with weight loss?

Brown fat, also known as brown adipose tissue, is very different from the white fat that surrounds our bellies and thighs.

This special tissue converts the calories we consume into heat, especially when it’s cold or when weight loss patients engage in extreme activities such as winter swimming or cryotherapy.

Scientists used to think that only babies had brown fat, but more recent research has shown that adults still retain some brown fat later in life. Unfortunately, people retain less and less brown fat as they age.

Another problem that stumped the researchers was figuring out what quickly shuts down brown fat before it has a chance to have a real impact on body weight in adulthood.

Thus, researchers from the University of Southern Denmark (SDU) and the University of Bonn, Germany, examined the genetic mechanisms that activate and deactivate brown fat.

Brown fat. Credit: SDU, April 29, 2024. New research has discovered the protein responsible for deactivating brown adipose tissue – AC3-AT

The team discovered that brown fat possesses a previously unknown built-in mechanism that shuts down its activity shortly after activation, preventing it from working for a long time. Specifically, the researchers identified a protein responsible for this shutdown process. This protein is called AC3-AT.

There are significant implications of this finding

The research team discovered the stop protein AC3-AT using advanced technology capable of identifying unknown gene products and was thus able to predict previously unknown proteins. They also studied mice in which AC3-AT had been artificially removed from their genomes.

The mice became better at burning calories

Animals lacking AC3-AT were protected against becoming overweight. Their bodies simply burned calories better and their metabolic rate increased because brown fat was activated, explains Hande Topel, a senior postdoctoral fellow in the research group of Professor Jan-Wilhelm Kornfeld at SDU, in a statement.

“Looking forward, we believe that finding ways to block AC3-AT could be a promising strategy to safely activate brown fat and address obesity and related health problems,” she says.

The AC3-AT protein is not only found in mice but also in humans and thus has direct therapeutic implications for humans.

Although the appearance of brown fat decreases with age in humans, some adults can still activate it. Cold exposure, such as outdoor baths in winter, triggers this activation. When the body encounters the cold, it has to do something extra to retain heat, and one of those mechanisms is to activate brown fat to generate heat.

By knowing how brown fat is deactivated, scientists can devise a way to keep this process activated more often, helping people burn more fat and reach a healthy weight.

In this study, the first step was to completely remove the off switch on this process so that nothing could stop brown fat’s heat producing capabilities.

“When we investigated mice that genetically lacked AC3-AT, we found that they were protected from becoming obese, in part because their bodies were simply better at burning calories and were able to increase their metabolic rates by activation of brown fat,” reports Topel.

In their experiments, the team followed two groups of mice that were fed a high-fat diet for 15 weeks – which led to obesity. One of these groups had the AC3-AT protein removed by genetic engineering.

The results of the study, published in Nature Metabolism, show that mice without the brown fat off switch gained less weight despite eating fatty foods. These mice were also metabolically healthier than other mice that still carried the genetic switch.

“Mice lacking the AC3-AT protein also accumulated less body fat and increased their lean mass compared to control mice,” says study co-author Ronja Kardinal, a PhD student at the University of Bonn. “Because AC3-AT is not only found in mice, but also in humans and other species, there are direct therapeutic implications for humans.”

Although people lose much of their brown fat with age, it is not impossible to activate this tissue and trigger weight loss. The easiest way to do this is simply by being cold.

If you exercise outdoors on a winter day, your body will activate brown fat, increasing fat metabolism

Scientists can now take these findings and figure out the best way to silence AC3-AT in obese patients and then expose them to cold environments that maximally activate this calorie-burning fat.

The AC3-AT protein was not the only relevant one the researchers found. They also discovered other previously unknown proteins or genetic variants that respond to cold in a similar way to AC3-AT. However, according to the researchers, it is too early to determine whether they can be used to activate brown fat in human treatments.

More research is still needed to discover the best way to turn our brown fat into the newest weapon against obesity.