Going for a walk in the cold after a meal could help people lose weight as low temperatures prompt the body to burn calories, research suggests.
Cool temperatures may activate “good” fat in the body that burns calories and ultimately leads to weight loss, according to a new study.
The “good fat” is called brown adipose tissue, or brown fat, and is naturally found in humans. It takes calories from normal white fat, which stores energy, and burns it. Past trials have shown that brown fat can be stimulated in mice, showing promising signs for future weight-loss therapies, but scientists have not shown how to successfully stimulate it in humans.
Researchers from the Joslin Diabetes Center in Boston wanted to compare the effects of ephedrine, a stimulant that is used in weight-loss drugs, versus the cool temperatures, which scientists predicted would activate the brown fat.
The team tested 10 study participants in three different ways. They were given injections of ephedrine, or saline solution as a control, or made to wear a “cooling vest,” which had 57-degree water pumping through it. Their fat activity was then measured.
Researchers found that brown fat was the same following both the ephedrine and saline injections. However, after the subjects wore the cooling vests for two hours, their brown fat activity was stimulated significantly.
Both interventions – ephedrine injections and the wearing of the cooling vests – did result in the same number of calories being burned, Dr Cypess noted.
He said: “But we found that ephedrine was not using brown fat to do it.
“This is the first time it has been found that ephedrine does not turn on brown fat.”
Both methods had effects on the sympathetic nervous system — which activates the fight or flight response — such as increased blood pressure.
But only the cold activated brown fat.
Dr Cypess said harnessing the cold effects could help reduce calories without the side effects associated with ephedrine.
He said: “Mild cold exposure stimulates (brown fat) energy expenditure with fewer other systemic effects, suggesting that cold activates specific sympathetic pathways.
“Agents that mimic cold activation of (brown fat) could provide a promising approach to treating obesity while minimizing systemic effects.”
One method may be simply to design cooling vests that people can wear to help them lose weight.
A future study will have subjects wear the vests for several weeks to see what happens, Dr Cypess said.
But Dr David Katz, director of the Yale Prevention Center, said neither ephedrine nor any type of cooling vest should be the go-to intervention for exercise and a good weight loss regime.
“One is unsafe, the other is uncomfortable,” said Katz. “If people are willing to put with discomfort, how about they try eating better and being more active?”