Your apartment’s thermostat doesn’t really give a damn if you’re trying to lose weight. However, it turns out that your body has its own thermostat, and a group of researchers in St. Louis spent more than ten years figuring out how to adjust it.
Irfan Lodhi’s lab at Washington University made the discovery, which was discreetly published in Nature this past September. His team discovered a backup heater inside brown fat cells that runs on tiny structures called peroxisomes, something that most physiology textbooks never mentioned. For a long time, scientists believed that mitochondria were the primary source of body heat. They were only partially correct.
| Information | Details |
|---|---|
| Research Institution | Washington University School of Medicine, St. Louis |
| Lead Researcher | Dr. Irfan J. Lodhi, Professor of Medicine |
| Department | Division of Endocrinology, Metabolism & Lipid Research |
| Study Published | September 17, 2025 |
| Journal | Nature |
| Key Discovery | Peroxisomes act as a backup heat source in brown fat |
| Critical Protein | Acyl-CoA oxidase 2 (ACOX2) |
| Test Subjects | Genetically engineered mice |
| Funding Source | National Institutes of Health (NIH) |
| Potential Application | Treatment for obesity and insulin resistance |
| Patent Status | Provisional patent filed by Washington University |
| Dietary Connection | Branched fatty acids found in dairy and breast milk |
The strange relative of the body’s storage system has always been brown fat. Like a doomsday prepper, white fat hoards calories. In contrast, brown fat burns through them, directly transforming energy into heat. Since they are still unable to shiver, babies rely on it. Though most of us never consider it unless we’re shivering at a bus stop in February, adults still carry pockets of it around the collarbone and along the spine.
Lodhi’s team discovered that mice do not just freeze when the typical heat-producing protein, UCP1, is knocked out. They continue to produce heat. Something else takes over. That something is ACOX2, a protein found inside peroxisomes that breaks down a specific type of branched fatty acid and produces heat as a byproduct. In order to observe it in real time, the team even constructed a fluorescent sensor.
This may fundamentally alter our understanding of metabolism. Mice that were genetically modified to produce more ACOX2 showed improved insulin sensitivity, tolerated cold better, and remained leaner on high-fat diets. Experiments that should have been routine caused the individuals lacking ACOX2 to gain weight and shiver. Before the manuscript’s ink had dried, the university filed a provisional patent due to the striking contrast.
Observing this field’s progress gives me the impression that we are slowly approaching something truly novel. For the past two years, Ozempic and its cousins have been the talk of the town, but their primary mechanism of action is appetite suppression. On the other side of the equation, Lodhi’s pathway operates. Instead of eating less, it burns more. Anyone who has attempted to lose weight and painfully found that hunger always prevails will find value in this distinction.
Dairy products, breast milk, and some gut microbes produce the branched fatty acids that ACOX2 metabolizes. People with higher circulating levels of these molecules typically have lower body mass indices, according to earlier research. No one could figure out why. Although Lodhi is careful to note that correlation does not equate to causation, there is now at least a tenable mechanism.
It’s still unclear if this turns into a pill, a probiotic, or something else entirely, like a yogurt sold for its metabolic benefits. Drug development is harsh and takes a long time. Studies on mice have a long, sometimes embarrassing history of poorly translating to humans. However, in just the past eighteen months, parallel research on beige fat and self-combusting cells has been published by Cornell, the BBC, and a few other labs. Something is coming together.
It’s difficult to ignore how frequently the body stores an extra key for its most crucial processes. It feels almost poetic to have a backup heater inside a fat cell. The question of whether we can learn to use it is still unanswered.
