YSM Issue 90.5

INN VATI N
STATION
Optimal Leaps in Optimizing Fat Burn
►BY HANNA MANDL
Society’s embrace of dietary interventions and increased
physical activity ensues to relieve obesity as a global health
threat, but such interventions can only go so far. Dieting and
exercise have seemingly helped athletes and those who wish
to shed a few extra pounds, but the market lacks an affordable,
accessible and accurate technology to monitor progress in
body fat loss. Consider bringing a ten-thousand-dollar mass
spectrometer—the necessary machinery to collect fat loss
data, comparable in size to an office printer—to the gym.
It may seem extreme to go to such lengths to measure fat
burning, but until now, there was little else to rely on.
New research curtails these concerns. Investigators at ETH
Zurich and the University Hospital Zurich have recently
developed a real-time breath acetone sensor to detect fat
burning through a person’s exhalations during physical
exercise. Andreas Güntner, a co-author of the study and a
postdoctoral researcher in the lab run by professor Sotiris
Pratsinis, explains that the group targeted acetone because
it is the most volatile byproduct of body fat burning, or
lipolysis. During body lipolysis, byproducts like acetone
move into the bloodstream and eventually find their way
to the pulmonary alveoli in the lungs, where they can be
released from the body via exhalation.
Detecting acetone in exhaled breaths is not very simple,
however. “It is rather challenging to accurately detect
acetone in breath as it occurs at trace level concentrations—
typically parts per million—among more than 800 chemical
species,” Güntner said. To solve this, the researchers decided
to coat the sensor with a highly porous film of tungsten
trioxide doped with silicon atoms. The highly porous nature
of this film allows for easy diffusion of gas molecules and
offers a large surface area for sensing acetone at various
concentrations. The researchers used silicon to stabilize the
tungsten trioxide because the resulting chemical compound
is highly sensitive, selective and stable, allowing for the
sensor to detect acetone exclusively.
To test the sensor, the team collaborated with pulmonary
specialists including the Director of the Department of
Pulmonology, Malcolm Kohler, at the University Hospital
Zurich. Twenty volunteers completed three thirty-minute
sessions of moderate cycling on an ergometer to stimulate
lipolysis, followed by a resting period. During and after the
periods of exercise, the researchers measured breath acetone
profiles by asking the volunteers to blow into a tube that was
fixed to the acetone sensor.
“We observed large variations from person to person,”
Güntner said. “While some volunteers showed increasing
breath acetone concentrations—indicating enhanced body
fat burn—already after a short work-out, it took some others
almost ninety minutes of training.” These results were confirmed
by mass spectrometry and not only indicated that the sensor
could successfully detect acetone as a marker of lipolysis,
but interestingly also provided insight into each volunteer’s
individual metabolic state. Parallel blood measurements of
the biomarker beta-hydroxybutyrate—a standard method
for monitoring body fat metabolism—agreed with the data
collected by the acetone breath sensor, ensuring that the acetone
sensor measurements were indeed accurate.
Alongside these results, the small size and low cost of this
acetone breath sensor prove it to be advantageous over other
similar instruments. According to Güntner, the chip is the
size of a one-cent euro coin (comparable in size to a US
dime) and is fabricated from low-cost components, making
it ideal for integration into a device that can be used at home
or at the gym. Current systems used to measure breath
acetone include indirect calorimetry and mass spectrometric
techniques—methods which are complex, lack portability
and cost thousands of dollars. Portable breath acetone tests
are already available for use, but existing models are either
inaccurate, not reusable, or incapable of detecting acetone
in real-time.
While the researchers refine their prototype breath
acetone sensor, health and fitness fans can look forward to a
new method of personalizing and optimizing their training
routines. The researchers are optimistic about the future
of their one-size-fits-all sensor. “I believe this device could
be quite attractive for athletes to optimize their training
regimens and personal fueling tactics,” Güntner said. “But
also for those who would like to guide dieting toward
effective fat loss.”
www.yalescientific.org
December 2017
Yale Scientific Magazine
35