Mice that ate a normal diet and resisted obesity anyway sat at the center of a puzzle that researchers at the Weizmann Institute of Science spent years trying to explain. The animals weren’t exercising more than usual. Their food intake wasn’t restricted. The only difference was that a single protein had been silenced in their muscle tissue – and somehow, that was enough to keep them lean no matter what they ate.
That protein is called MTCH2, nicknamed “Mitch.” And in research published earlier this year, the same team showed that flipping this fat-burning switch in human cells produces a remarkably similar effect: cells burn through fat and carbohydrates faster, and the formation of new fat cells slows dramatically. The implications are significant enough that the lab is now working with partners to develop a drug based on the finding.
Before getting into what the protein does, it’s worth establishing what makes its discovery unusual. MTCH2 sits on the outer membrane of mitochondria, the energy-producing structures inside every cell. Most proteins studied in obesity research are involved in appetite signaling or fat storage directly. This one regulates how mitochondria are physically organized – and through that, how aggressively cells burn fuel.
What MTCH2 Does Inside Your Cells
Scientists at the Weizmann Institute identified a protein called MTCH2, nicknamed “Mitch,” that plays a major role in how cells manage energy and store fat. The protein sits on the outer membrane of the mitochondria – the tiny structures inside every cell that convert food into usable energy. Mitochondria can fuse together, forming an extensive network of power plants that are highly efficient producers of energy, or they can exist as separate organelles that are less efficient at generating energy.
Mitch controls which of those two states the mitochondria occupy. When the protein is present and active, mitochondria link up into those larger, more productive networks. When it’s gone, the network collapses. Disabling this protein in human cells increases the rate at which fats and carbohydrates are burned while also reducing the formation of new fat cells.
The MTCH2-free cells took up more glucose, showed higher oxygen consumption, and burned through amino acids, carbohydrates, and fats. The cells entered a hypermetabolic state – they needed more energy and used more raw material to get it. With Mitch gone, the cell effectively acts like it’s in an energy emergency, burning everything available rather than setting fat aside for later.
In the new study, led by doctoral student Sabita Chourasia of the Weizmann Institute’s Department of Immunology and Regenerative Biology, researchers used genetic engineering to remove MTCH2 from human cells grown in the lab. “After deleting Mitch, we examined, every few hours, the effect that had on more than 100 substances taking part in metabolism in human cells,” Chourasia said in a statement. “We saw an increase in cellular respiration, the process in which the cell produces energy from nutrients, such as carbohydrates and fats, using oxygen.”
The Mouse Discovery That Started It All
The human cell experiments built on an earlier, almost accidental finding. Several years ago, Professor Atan Gross of the Weizmann Institute came upon a possible solution while studying mouse genes. When he and his team silenced the expression of the MTCH2 protein in muscles of mice, these mice developed increased athletic capacity and were “immune” to obesity, thanks to an accelerated rate of metabolism.
The results in those animals went well beyond simple fat loss. The rodents seemed like they could not grow obese no matter how much food they ate. They also grew more oxygen-hungry muscle fibers and performed better in physical stress tests. Their heart function improved too. For researchers studying obesity, that combination – less fat, more muscle, better endurance – is almost exactly what a drug developer would want to reproduce.
MTCH2 is an obesity susceptibility gene. Adipose-specific MTCH2 depletion in mice protects against high-fat-diet-induced obesity and metabolic disorders. MTCH2 deficiency promotes energy expenditure by stimulating thermogenesis in brown adipose tissue and browning of subcutaneous white adipose tissue, accompanied by upregulated UCP1 protein expression, enhanced mitochondrial biogenesis, and increased lipolysis.
Why Blocking Fat Cell Formation Is Just as Important as Burning Fat
Most conversations about obesity focus on burning existing fat. This research adds a second front: stopping new fat cells from forming in the first place. The absence of MTCH2 prevents the formation of new fat cells – persistent energy deficiency reduces the activity of genes required for converting ordinary cells into fat cells, thereby decreasing fat accumulation.
Fat cells don’t spring into existence fully formed. They develop from precursor cells – immature cells called fat progenitors that must accumulate enough energy and building materials to complete the transformation into fat-storing cells. With Mitch disabled, those precursor cells simply can’t gather enough resources to finish the job.
This also connects to a finding specific to human biology. When researchers silenced MTCH2 in muscles of mice, those mice developed increased athletic capacity and were “immune” to obesity. The team then showed that in human cells, silencing Mitch both increases the rate at which fats and carbohydrates are burned and inhibits the development of new fat cells. Separately, researchers also noted that women with obesity tend to have elevated levels of the Mitch protein, suggesting higher natural MTCH2 activity may be part of why fat accumulates more readily in that population.
For more on the relationship between mitochondrial function and body composition, this Hearty Soul piece on Ozempic and bone loss covers what happens when weight loss comes at the expense of lean tissue.
The Problem with Current Weight-Loss Drugs
The Mitch discovery arrives at a moment when the limitations of existing obesity treatments are under scrutiny. GLP-1 receptor agonists – the class of medications that includes semaglutide (sold as Ozempic and Wegovy) and tirzepatide (Mounjaro and Zepbound) – have reshaped how doctors treat obesity. But they come with a significant tradeoff that the Weizmann research may eventually help solve.
Up to 40% of the weight lost with GLP-1 receptor agonists comes from lean body mass, raising concerns about potential adverse effects on skeletal muscle function. GLP-1 receptor agonists have been pivotal for obesity treatment, achieving 15 to 25 percent weight loss over 12 to 24 months, but questions remain about the potential influence of concomitant losses in muscle mass.
Losing that much muscle alongside fat isn’t a cosmetic concern. Muscle is metabolically active tissue – it burns calories even at rest, supports bone density, and plays a central role in blood sugar regulation. Losing it alongside fat can leave patients lighter but metabolically worse off, particularly older adults. Given that cessation of GLP-1 treatment often leads to significant weight regain, older adults may be at risk for sarcopenic obesity – a condition characterized by excessive adiposity and low skeletal muscle mass, which is prevalent in 10 to 20 percent of older adults.
Scientists at the Weizmann Institute found that the MTCH2 protein determines how cells decide whether to hang onto fat or burn it for energy. The discovery could lead to a new kind of obesity treatment that doesn’t cause muscle loss. In mouse experiments, removing Mitch didn’t just preserve muscle – it added muscle fibers and improved physical endurance, a result essentially the opposite of what current drugs produce.
The Scale of the Problem the Fat Burning Switch Could Address
The obesity epidemic’s numbers have shifted recently. Among U.S. children and teenagers, 21.1 percent have obesity, up from 19.3 percent in 2017-2018, according to CDC data from August 2021 to August 2023. For adults, the same CDC data put the obesity prevalence at 40.3 percent – with severe obesity affecting a further 9.7 percent of the adult population. The burden extends across age groups, and with obesity comes increased risk of cardiovascular disease, type 2 diabetes, liver disease, musculoskeletal disease, sleep apnea, and many cancers.
A treatment that could burn fat without stripping muscle would represent a meaningful clinical improvement over what’s currently available – and the MTCH2 research points toward exactly that possibility.
Where the Research Goes Next
Professor Gross’s lab is currently working, in collaboration with Bina – the Weizmann Institute’s translational research unit that identifies early-stage projects with applicative potential – on a comprehensive program to develop a novel small molecule that inhibits Mitch and may serve as an effective treatment for obesity. The program is being carried out in partnership with Yeda Research and Development Company, Weizmann’s technology transfer arm.
A “small molecule” in this context means a drug compound small enough to enter cells and interact directly with a target protein – the standard format for most oral medications. Yeda has confirmed MTCH2 as one of its active development targets, with the goal of finding a compound that inhibits the protein’s function in a controlled, therapeutic way.
The research remains early-stage. All the human data so far comes from cells in a lab, not from clinical trials in people. The mouse results are encouraging, but animal studies frequently don’t translate directly to humans. Scientists will need to establish that a Mitch-inhibiting compound is safe, that it can be delivered effectively, and that its effects in a living human system match what was observed in isolated cells. That process typically takes years.
What This Means for You
No Mitch-targeting treatment is available now, and none is likely to reach patients for at least several years, assuming the drug development program succeeds at all. Anyone who sees claims online about activating or blocking MTCH2 through supplements or dietary changes should treat them with skepticism – nothing in the current research supports those claims.
What the findings do offer is a more precise picture of how fat storage works at the cellular level. The fat burning switch that the Weizmann team identified isn’t a metaphor – it’s a real protein with a documented mechanism. Mitochondrial health, long understood to matter for energy levels and aging, now appears central to whether the body accumulates fat cells or burns fuel instead. Consistent aerobic exercise, adequate protein intake, and avoiding chronic sleep deprivation are all independently linked to better mitochondrial efficiency, even without any pharmaceutical intervention.
The research, published in The EMBO Journal, marks a genuine step forward in understanding why fat accumulates – and how that process might one day be redirected.
Disclaimer: This information is not intended to be a substitute for professional medical advice, diagnosis, or treatment and is for information only. Always seek the advice of your physician or another qualified health provider with any questions about your medical condition and/or current medication. Do not disregard professional medical advice or delay seeking advice or treatment because of something you have read here.
AI Disclaimer: This article was created with the assistance of AI tools and reviewed by a human editor.
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