Harvard scientists find that cold temperatures can help people lose weight

More than 40 percent of adult Americans are obese, a complex condition that increases the risk of diabetes, heart disease and several types of cancer. Obesity is a factor that can lead to other health problems by creating low-grade chronic inflammation and a buildup of immune cells in insulin-sensitive tissues. Scientists believe that reversing or "solving" this chronic inflammation may delay the onset of obesity-related diseases such as diabetes, and perhaps make weight loss easier.

Researchers from Brigham and Women's Hospital and the Joslin Diabetes Center found that exposure to low temperatures improved insulin sensitivity and glucose tolerance while addressing obesity-induced inflammation in diet-induced obese mice. Their findings are published in a new paper in Nature Metablism.

The team also found that the mechanism depends on brown adipose tissue, commonly referred to as "good fat," releasing a naturally occurring molecule called Maresin 2 in response to cold stimulation. Brown adipose tissue is known as an active endocrine organ because it secretes molecules that communicate with other tissues and manage metabolism. It also helps release stored energy and can promote weight loss and metabolic health.

"Substantial evidence suggests that obesity and metabolic syndrome are associated with chronic inflammation that contributes to systemic insulin resistance, so disrupting inflammation in obesity may offer promising therapies for obesity-related diseases," said Jocelyn Jocelyn, co-corresponding author of the study's paper. "We found that cold exposure reduced inflammation and improved metabolism in obesity, at least in part by activating brown adipose tissue," said Yu-Hua Tseng, PhD, senior investigator in the Division of Integrative Physiology and Metabolism at the Diabetes Center and professor of medicine at Harvard Medical School. These findings suggest that brown adipose tissue has a previously unrecognized function in promoting inflammation that addresses obesity."

In two earlier experiments, Tseng and colleagues found that brown fat may be activated by cold exposure to produce certain lipid mediators that control nutrient metabolism. In the current study, the researchers identified a novel role for a lipid mediator produced by brown fat in addressing inflammation.

In the current study, the researchers created a mouse model that develops obesity when given a standard high-fat, Western diet.

When the animals were exposed to the cold (about 40 degrees Fahrenheit), the researchers observed improvements in insulin sensitivity and glucose metabolism in the animals, compared to control animals kept in a temperature-neutral zone, and their body weight There's also a drop -- at this ambient temperature, the body doesn't need to generate heat to maintain its core body temperature.

What's more, the scientists also noticed a profound improvement in inflammation, as measured by lower levels of a major marker of inflammation.

"We found that brown fat produces Maresin 2, which addresses inflammation in the system and in the liver," said co-corresponding author Matthew Spite, principal investigator at Brigham and Women's Hospital and associate professor of anesthesiology at Harvard Medical School. , brown adipose tissue has a previously unrecognized function in promoting resolution of inflammation in obesity by producing this important lipid mediator."

In addition, these findings suggest that Maresin 2 could have clinical applications as a treatment for obesity, metabolic disease, or other conditions associated with chronic inflammation; however, the molecule itself breaks down rapidly in the body. Tseng and colleagues are seeking a more stable chemical analog for clinical use.

The team points out that shortcuts to improving metabolic health may already exist. Multiple human studies in Joslin and elsewhere have shown that exposure to mild low temperatures (50 to 55 degrees Fahrenheit) has been shown to be sufficient to activate brown adipose tissue and improve metabolism, although the mechanism is not well understood.