Scientists at Monash University's Biomedicine Discovery Institute believe they have found a mechanism in the brain that coordinates the conversion of food into white fat or brown fat in the body.
The study was conducted on mice, but evidence suggests it would likely apply to humans as well.
White fat is how humans store energy, and excess storage leads to obesity, while brown fat actually produces heat and burns energy.
When working properly, researchers believe this mechanism increases the amount of energy converted into brown fat, or browning, in response to eating, boosting the body's energy expenditure.
On the flipside, it decreases browning in response to fasting to encourage the body to store energy, or fat. The body is able to switch between the two when required.
The system is meant to help regulate the body's weight and prevent excess gain or loss, lead researcher Tony Tiganis said.
"In obesity, the whole switch didn't work. So feeding is not accompanied by browning, resulting in weight gain," he said.
"Specific mechanisms that normally should ensure the energy we eat is matched by a change in energy expenditure … these mechanisms are broken."
Stress may be a cause of 'broken' switch
Professor Tiganis said the study added further weight to the idea obesity was not just caused by the food a person ate.
"The key thing to recognise is that energy is homeostatically controlled, so the amount of food we eat should be matched by the amount of energy we expend," he said.
"The brain is instrumental in controlling and balancing energy intake with energy expenditure. It's not as simple as just changing your diet.
"We need to rebalance the energy intake, energy output equation so the food we eat is matched by the amount of energy we expend.
Professor Tiganis said they had not yet found the cause of the broken switch, but one theory was increased stress, which has been noted in mice.
"The stress may be preventing that food, that energy that you've taken in, from being burnt as it normally would be," he said.
"Our goal is to rewire this brain switch, fix this brain switch if you like, so that we once more turn on browning, promote energy expenditure response to feeding and thereby promote weight loss in obesity."
Exposure to cold another way to boost brown fat
There is another way to boost the burning of brown fat, through what's is known as cold thermogenesis.
That's the process of heat production, or energy burning, stimulated by exposure to very cold temperatures.
It's used by mammals and notably babies who have not yet developed the ability to shiver, to protect themselves against the elements.
Professor Tiganis said modern humans no longer rely on the process to keep warm, like our ancient cousins.
"Cold thermogenesis another way to promote browning in evolution, but not as important as it once was," he said.
"Now, when we're cold we just put on a jumper."