Breath, not blood: Device measures fat burning in exhaled air
ETH Zurich
image:
The Nutrion breath acetone analyser is operated via a smartphone app and allows the self-monitoring of breath acetone as a biomarker for fat metabolism.
view moreCredit: Alivion AG
Acetone is the by-product of fat metabolism that is exhaled via the lungs. It is made when the body burns fat instead of carbohydrates such as sugar. Researchers from ETH Zurich have developed a breath test device that can detect acetone in exhaled air with high precision. The device is very reminiscent of the alcohol breathalysers used by the police in traffic checks and can be operated reliably by non-experts in combination with a smartphone app. People can therefore monitor their fat metabolism without professional support or blood tests. This could eventually allow diets, treatments for metabolic disorders like diabetes, and ketogenic therapies used for example for epilepsy to be monitored more closely and tailored to individual patients.
“When it comes to diets, there’s no rule of thumb that works for everybody. Ideally, people should self-monitor to see how their own metabolism responds,” explains Andreas Güntner, Professor of Molecular Sensing at ETH Zurich’s Department of Mechanical and Process Engineering. “Methods are also needed that can be carried out independently and that produce reliable results, similar to blood glucose measurements for diabetics.” Güntner’s research group developed the measuring device in collaboration with the ETH spin-off Alivion, and tested its reliability together with the University Hospital Zurich.
Precise measurements outside the lab
In a validation study involving 12 adults, the researchers compared 312 breath readings recorded with the new measuring device with blood test results and measurements from a high-precision mass spectrometer – the analytical gold standard. The measurements were carried out using different metabolic scenarios: with light and intensive physical activity and various diets. This revealed that the results from the hand-held device were practically identical to those from the lab. In addition, the new measuring device delivered reliable results over a period of months.
In essence, the recently tested hand-held device is based on a sensor technology that has been in development at ETH Zurich for over 10 years and was presented for the first time in 2017. Already at the time, Güntner and his co-authors were able to demonstrate that the gas sensors they had developed were so sensitive that they could detect a single acetone molecule in a hundred million other molecules.
Reproducible readings thanks to filter and app
According to the researchers, readings from currently available acetone breathalysers have only limited reproducibility and can only detect pronounced metabolic changes. They not only respond to acetone, but also to other components of exhaled air, for example if test subjects ate or drunk something beforehand.
The researchers therefore developed a filter that blocks interfering molecules, and a smartphone app that guides test subjects in real time as they exhale. “The device measures the volume of exhaled air and only takes a sample that comes from deep in the lungs after a certain time,” says lead author Simone Hersberger, adding: “otherwise, every reading would be slightly different.” In order for this to work, the devices are initially calibrated and adjusted to the patient’s lung volume.
From basic research to product
The successful validation study is an important milestone for the researchers. “We were able to demonstrate that our device can detect slight differences in fat metabolism accurately and reliably,” says ETH doctoral student Hersberger. Further studies are now intended to show whether the new measuring device can really be used to personalise therapies for metabolic disorders. In partnership with the University Children’s Hospital Zurich, the researchers are currently looking at whether the hand-held device can help children with epilepsy better monitor their ketogenic diet. Other fields of application are the monitoring and optimisation of medical diets or of so-called GLP-1 therapies with weight loss jabs. Applications in amateur sports are also being considered.
The ETH spin-off Alivion AG has launched the device under the name ‘Nutrion’. It is currently being deployed in international research studies and in medical facilities. To scale up further and to open up further fields of application, Alivion is seeking additional industry partners and strategic investors. “This example shows how the results of basic research can be put into practice and ultimately help society,” says ETH professor Andreas Güntner.
This work is being financially supported by Innosuisse, the Vontobel Foundation and the Accentus Foundation.
Article Title
Self-monitoring of Fat Metabolic Status with Smartphone-assisted Breath Acetone Detector
Breathalyzer that sniffs out when your body starts burning fat
Cell Press
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A user performs a breath measurement with the smartphone-assisted breath acetone analyzer.
view moreCredit: Alivion AG
Researchers have developed a breath detector with a chemical sensor that sniffs out when your body is burning fat through a single exhale. Reporting on July 22 in the Cell Press journal Device, the handheld, smartphone-assisted device measures acetone—a molecule that is released into the breath when the body burns fat—in about 90 seconds with laboratory-level accuracy. The technology could help people monitor their metabolism and allow clinicians to personalize treatments for obesity, diabetes, epilepsy, and other metabolic conditions.
Scientists have long used breath acetone as a window into metabolism because its concentration rises as the body shifts from using carbohydrates to fat. But doing so typically requires bulky laboratory instruments or consumer devices that work reliably only at very high acetone levels.
“If we want to make that information available to patients, we need to shrink those technologies into compact, user-friendly devices,” says senior author Andreas Güntner of ETH Zurich. After 10 years of engineering, the team finally built a portable, highly sensitive breath acetone detector for everyday use.
To evaluate the detector, the team tested it with 12 healthy adults under real-world conditions. The handheld detector measured acetone concentrations from 0.2 to 45 parts per million across 312 breath samples. The measurements closely matched those from mass spectrometry—the laboratory gold standard for breath acetone analysis.
The team then monitored breath acetone in four metabolic scenarios: light exercise followed by a high-carb meal, intense exercise followed by a high-carb meal, a fat-rich ketogenic meal, and fasting. They compared the breath measurements with metabolic markers, including blood ketone and glucose, to determine how well the detector tracked changes.
Breath acetone remained low after light exercise followed by a high-carb meal but rose in scenarios of intense exercise, reflecting the body’s increased reliance on fat as a fuel source. Following intense exercise, the participants’ acetone levels dropped after a high-carb meal, remained elevated after a fat-rich meal, and continued to increase during fasting, mirroring changes seen in blood and glucose markers.
“These findings show that we have the high performance needed for applications such as clinical studies, where you really want to distinguish these slight differences in fat metabolism,” says first author Simone Hersberger of ETH Zurich.
For real-world applications, Hersberger says that ease of use and controlled breath sampling are key priorities. During every measurement, the smartphone app coaches users to exhale with the right force and duration for reproducibility. Built-in quality controls can even reject improper breaths or contaminated air to ensure reliable data.
The technology has already moved beyond the laboratory. ETH spin-off Alivion AG has commercialized the breath acetone analyzer under the name “Nutrion.” This handheld device is now being used in clinical studies for epilepsy and by individuals interested in tracking their breath acetone levels as a marker of fat metabolism for weight loss and athletic performance.
“Now it's really time to spread it out into clinical trials and answer questions such as the effectiveness of different fasting therapies by providing personalized guidance,” says Güntner. “We're really moving toward healthcare solutions that, in the future, you won't need to go to the hospital for anymore. You'll be able to do them at home.”
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This work was supported by funding from Innosuisse, the Vontobel-Stiftung, Stiftung Accentus Fonds Thimonia, Verena Guggisberg-Luthi, and the Swiss State Secretariat for Education, Research and Innovation (SERI).
Device, Hersberger et al., “Self-monitoring of fat metabolic status with smartphone-assisted breath acetone detector” https://www.cell.com/device/fulltext/S2666-9986(26)00178-X
Device (@Device_CP), is a physical science journal from Cell Press along with Chem, Joule, and Matter. Device aims to be the breakthrough journal to support device- and application-oriented research from all disciplines, including applied physics, applied materials, nanotechnology, robotics, energy research, chemistry, and biotechnology under a single title that focuses on the integration of these diverse disciplines in the creation of the cutting-edge technology of tomorrow. Visit http://www.cell.com/device/home. To receive Cell Press media alerts, contact press@cell.com.
Journal
Device
Method of Research
Experimental study
Subject of Research
People
Article Title
Self-monitoring of fat metabolic status with smartphone-assisted breath acetone detector
Article Publication Date
22-Jul-2026
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