Contact: Jeremy Craig
Georgia State University
Georgia State researchers shed light on fat burning
ATLANTA — Researchers at Georgia
State University have found that fat cells give feedback to the brain
in order to regulate fat burning much the same way a thermostat
regulates temperature inside a house.
With as increase in
obesity threatening the health and life expectancies of people across
the world, the research may help scientists better understand how
weight is shed.
C. Kay Song and Tim Bartness of Georgia State,
along with Gary J. Schwartz of the Albert Einstein College of Medicine,
found that during the process of burning fat — called lipolysis — fat
cells use sensory nerves to feed information to the brain.
viruses to trace communications in the nerves of Siberian hamsters,
they found that the brain uses part of the nervous system used to
regulate body functions, called the sympathetic nervous system, to in
turn communicate back to the cells to initiate, continue or stop the
fat burning depending upon the information the brain receives from the
"The brain can trigger lipid burning by fat cells and
through these sensory nerves, the fat cell can give the brain
feedback," Bartness explained. "This is a really important concept in
biology, as it can regulate the process of lipolysis much like how a
thermostat regulates temperature in your house, using input from the
air and output to a furnace or heating unit.
"The presence and function of the sensory nerves has been completely
ignored and the areas in the brain that receive this sensory
information were unknown until we did these studies," he said.
the body has a low amount of a type of readily available fuel, a
carbohydrate called glycogen, the body starts lipolysis to release
energy stored in fats. At the end nerves which are part of the
sympathetic nervous system, a chemical called norepinephrine is
released to trigger the breakdown of fat.
then appear to report back to the brain to inform it of the status of
the lipolysis, communicating whether too much or too little energy has
been released — and the activity of the sympathetic nerves can be
"If you're doing a moderate amount of
exercise or even if it has been a fairly long interval since you last
ate, you will use up all or most of the available glycogen,
necessitating the break down fat to yield sufficient energy," he said.
"But you don't want to break down more than you need. So, this would be
a way to stop the sympathetic nervous system from triggering the
release of too much lipid energy from fat."
Bartness said that though this communication process is known to
play a role in the short-term burning of fat, researchers are not sure
whether this process is involved with the long-term issues of burning
fat — important in understanding obesity and why some people burn fat
more readily than others.
"It could be that sensory nerves
have a dual function," he explained. "In addition to the
moment-to-moment lipolysis process, they might also have a longer term
function. It's complicated, and it might be a different subset of the
sensory nerves performing the long-term monitoring of fat reserves."
The research appears in the March edition of the
American Journal of Physiology: Regulatory, Integrative and Comparative Physiology.