Old Compound TOFA Boosts Fat Burning in Mice

Adults on weight-loss drugs may one day benefit from this combination, though it has so far been tested only in mice.

Updated on Nov. 3, 2026 in Weight Loss

Old Compound TOFA Boosts Fat Burning in Mice

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Would you be interested in a weight-loss drug that boosts calorie burning rather than curbing appetite?

University of California, Berkeley researchers reported that TOFA, an experimental compound first made in the 1970s, causes cells to burn fat for energy. In mice, combining low doses of TOFA with semaglutide or tirzepatide produced far greater weight loss than either drug alone, though the work has not yet been tested in humans.

Why it matters

Existing weight-loss drugs can remove a meaningful share of muscle along with fat, which matters for long-term health and function. Researchers revisited an old laboratory compound and found a fat-burning effect, suggesting a possible route to losing more fat while preserving lean tissue, though this is early-stage research.

This is a mouse study in which obese animals received TOFA alone, low-dose semaglutide or tirzepatide alone, or combinations of them. Almost all weight lost by the TOFA-treated mice was fat, with no significant loss of lean tissue, but the findings have not been replicated in people.

The players

University of California, Berkeley

A public research university whose scientists led the study of TOFA's effects on fat metabolism and weight loss in mice.

University of Glasgow

A Scottish public university whose metabolic researcher Naveed Sattar commented on the findings.

Ulster University

A Northern Irish public university whose researcher Alex Miras commented on the findings.

The details

TOFA blocks enzymes involved in building new fat and activates two proteins that switch on genes involved in burning fat and producing energy. Rather than mimicking a natural hormone, it acts on several pathways tied to fat metabolism. In the mouse experiments, low doses of semaglutide or tirzepatide were combined with TOFA, and the combinations produced substantially greater weight loss than either component alone.

TOFA was created as a manmade compound in the 1970s but was never developed into a medicine.
Obese mice on TOFA lost about 18 per cent of body weight over four weeks.
The combination dosing trial measured weight loss in mice over 24 days.
Combination mice lost 26 per cent of body weight after ten days, prompting researchers to halve the dose.

Health Landscape

Current obesity drugs such as semaglutide and tirzepatide produce substantial weight loss, but a notable share of that loss is muscle. This line of research points toward combination approaches that target fat metabolism directly, though none has yet reached human trials.

This research is at an early stage and does not change current care, so there is nothing to start or stop based on it. If you are considering weight-loss medication, it is worth discussing with your doctor which approaches fit your health history and how muscle preservation fits into your plan.

The takeaway

The most useful insight here is that weight loss may be shaped not only by how much you lose but by whether the loss is fat or muscle. Ask your physician about body-composition goals when discussing any weight-loss treatment, and watch for human trial results before drawing conclusions about TOFA.