Blowing instead of Bleeding Device Measures Fat Burning in Breath

Researchers at ETH Zurich (Switzerland) have developed a portable measuring device that detects the fat metabolism biomarker acetone in breath almost as precisely as a mass spectrometer. It can be operated by non-experts and identifies when the body starts burning fat during a diet or exercise.

Acetone is a byproduct of fat metabolism that is exhaled through the lungs. It is produced when the body burns fat instead of carbohydrates like sugar. Researchers at ETH Zurich have developed a breath test device that can measure acetone in exhaled air with high precision. The device closely resembles the alcohol test devices used by police at traffic checks and can be reliably operated by laypersons in conjunction with a smartphone app. This allows individuals to monitor their fat metabolism without professional assistance or blood tests. In the future, this could enable more precise monitoring and personalization of diets or treatments for metabolic diseases such as diabetes, as well as ketogenic therapies used, for example, in the treatment of epilepsy.

"There is no one-size-fits-all approach to dieting. Ideally, individuals should monitor themselves to see how their metabolism reacts," explains Andreas Güntner, Professor of Sensor Technology at the Department of Mechanical and Process Engineering at ETH Zurich. "This requires methods that, similar to blood sugar measurements for diabetics, can be performed independently and provide reliable results." Güntner's research group developed the measuring device together with the ETH spin-off Alivion and tested its reliability in collaboration with the University Hospital Zurich.

Precise Measurement Results Outside the Laboratory

In a validation study with twelve adult participants, the researchers compared 312 breath measurements taken with the new device to blood tests and a highly precise mass spectrometer—the analytical gold standard. The measurements were conducted under various metabolic scenarios: during light and intense physical activity and with different diets. It was shown that the results of the handheld device were practically identical to those from the laboratory. Additionally, the new device delivered reliable results over several months.

At its core, the tested handheld device is based on a sensor technology whose development began over 10 years ago at ETH Zurich and was first introduced in 2017. Even then, Güntner and his co-authors were able to demonstrate that the gas sensors they developed are so sensitive that they can detect individual acetone molecules among hundreds of millions of other molecules.

Reproducible thanks to Filter and App

Although breath acetone devices are already available today, their measurements are only limitedly reproducible and can only detect pronounced metabolic changes. They respond not only to acetone but also to other components in the breath, for example, if participants have eaten or drunk something beforehand.

The researchers have therefore developed a filter that blocks interfering molecules and a smartphone app that guides participants in real-time during exhalation. "The device measures the exhaled volume and only takes a sample after a certain time, which comes from deep in the lungs," says lead author Simone Hersberger, adding: "Otherwise, every measurement would turn out slightly differently." To ensure this works, the devices are first calibrated and adjusted to the individual lung volume of the patients.

From Basic Research to Product

With the successful validation study, the researchers have reached an important milestone. "We were able to demonstrate that our device precisely and reliably detects slight differences in fat metabolism," says ETH doctoral student Hersberger. Further studies aim to determine whether the new measuring device can truly be used to personalize therapies for metabolic diseases. In collaboration with the Zurich Children's Hospital, the researchers are currently investigating whether the handheld device can help children with epilepsy better monitor their ketogenic diet. Other application fields include monitoring and optimizing medical diets or GLP-1 therapies using a "weight-loss injection." Applications in recreational sports are also under discussion.

The ETH spin-off Alivion AG has brought the device to market under the name "Nutrion." Currently, Nutrion is being used in international research studies and medical facilities. To further scale its operations and expand into additional application fields, Alivion is seeking additional industry partners and investors. "This example shows how results from fundamental research can be translated into practical applications and ultimately benefit society," says ETH Professor Andreas Güntner.