As a cyclist, it’s reached the time of year where training tends to be all about building your ‘base’.  The theory goes that you build up some endurance and promote your bodies ability to burn fat for energy rather than glycogen.

Of course, figuring out if you’re actually doing that is easier said than done, but a team from ETH Zurich have developed a sensor that analyzes your breath and can tell you if you’re in the ‘fat burning zone’.  The work, which was documented in a recently published paper, provides a real-time monitor for lipolysis by analyzing our exhalations during exercise.

“When burning fat, the body produces by-products that find their way into the blood,” the researchers explain. “This would allow athletes and people who want to lose weight to check for themselves when their bodies begin to burn fat…”

The fat burning zone

The key substance the team were looking for is called acetone.  The sensor they’ve developed to detect it is believed to be one of the most sensitive ever built.  It’s capable of detecting a single acetone molecule in 100 million other molecules.

The system was put through its paces with a team of volunteers that were asked to complete a 90 minute session on a bicycle ergometer.  Each volunteer was kitted out with a tube into which they were asked to blow, with the sensor monitoring their acetone levels.

“We were able to show how the acetone concentration in the exhalations varies greatly from person to person,” the authors say.

The analysis revealed that there was a high level of variance in each volunteer, with some beginning to burn fat much earlier in the session than others.  The analysis also revealed that the breath based method was as effective and accurate as the blood analyses typically used today for monitoring lipolysis.

Smart sensing

The sensor itself uses a porous film made of semiconducting nanoparticles made of tungsten trioxide.  Each particle is implanted with silicon atoms.  It’s a project that has been several years in development, with the team initially discovering that trioxide nanoparticles were able to interact with acetone if the atoms are arranged in the right way.  This in turn reduces the electrical resistance on the chip, thus allowing measurement to take place.

The team originally planned to use the device to diagnose diabetes.  It’s well known that those with undiagnosed type 1 diabetes have high concentrations of acetone in their breath.  The sensor is so effective however, that it can also be used to detect low levels of acetone as we exhale during exercise.

“This would allow athletes and people who want to lose weight to check for themselves when their bodies begin to burn fat so that they can optimize their training regimen,” the researchers say.

Whilst measuring our fat burning capabilities is possible today, it is typically only possible in a lab environment with incredibly expensive equipment.  The team have used these to calibrate their sensor, with positive initial comparisons.  They hope that their device will allow for real-time measurements to be taken every day.  There is already a prototype of the device, with the next step being to develop this further and hopefully bring it to market.