The study involved 47 adults with overweight or obesity, according to multiple reports. 3 lb) on average. The weight loss could not be accounted for by increased exercise, the researchers said.
The research was conducted by teams at the University of Nottingham and Leiden University Medical Center, jointly funded by the Dutch Heart Foundation and the British Heart Foundation. The cooling vests contain pockets for frozen gel packs and are worn over a thin T-shirt. This is the first real-world investigation of cold exposure for weight loss in overweight people.
Brown adipose tissue (BAT) is activated by cold exposure and burns calories to generate heat. Unlike white fat that stores energy, brown fat burns energy, making it a key part of metabolism. Daily cold exposure activates brown fat, which uses body fat stores to produce heat, according to Professor Helen Budge of the University of Nottingham.
Mild cold exposure can change some white fat cells into beige fat, which is richer in mitochondria. Long-term brown fat activation using mild cold exposure has been proven in mouse studies to cause weight loss and treat obesity and diabetes. Consistent cold exposure increases BAT amounts, as seen in outdoor seasonal workers.
Brown fat also releases substances that help control blood sugar and improve muscle and liver function. A personalized cooling protocol based on shivering threshold can activate BAT in young adults. In a study of 47 adults, 85% were PET-positive for BAT after personalized cooling, with women showing higher BAT mean activity than men.
The Cool Fat Burner vest can activate brown fat and keep it active for over an hour after removal. A cooling vest can activate brown fat, as shown by a one-third increase in blood nonesterified fatty acids, according to Canadian researchers in the Journal of Clinical Investigation. Cold exposure is a consistent method to activate brown fat, said Aaron Cypess.
Cooling vests may boost metabolism without exercise by leveraging skeletal thermogenesis. The metabolic response to cold exposure varies based on time of day and gender, according to a Leiden University Medical Center study presented at ECO 2023. In men, cold-induced energy expenditure and skin temperature were higher in the morning than evening.
In women, there was no significant difference in cold-induced energy expenditure between morning and evening. Women had greater cold tolerance in the morning and higher circulating free fatty acids after morning cold exposure. Cold exposure in the morning may be more effective at boosting metabolism and burning fat in men, but not in women, said Mariëtte Boon of Leiden University Medical Center.
However, women showed higher brown adipose tissue mean activity than men after personalized cooling, suggesting the sex-specific effects may depend on the outcome measured. Researchers are launching a new trial to investigate whether a 90-second cold shower each morning has the same fat-loss effect. A trial is also exploring how cooling vests and overnight fasting influence metabolism.
The cooling vest is a much longer period of exposure than a cold shower, but the cold shower is much colder, Dr. Boon noted. We will have to see if it has an impact on weight loss, she added.
Cold swimming is not directly comparable to cooling vests due to other effects like cold shock, Budge said. The study comes amid a growing health trend of cold water swimming, with advocates including the Princess of Wales, according to reports. Ephedrine did not reliably activate brown fat in a study comparing ephedrine, saline, and cold exposure, according to Aaron Cypess of the Joslin Diabetes Center.
Cooling vests are generally safe and well-tolerated. Cold exposure offers another lifestyle choice for people wanting to lose weight and is important for health, Budge said, adding that it could help with heart disease. Vests like this can be worn at home and so cold exposure could be a simple and inexpensive addition to lifestyle strategies for weight loss such as healthy eating and physical activity, Boon added.
The long-term efficacy and safety of daily cold exposure for weight loss in larger, more diverse populations remain unknown. The optimal duration, temperature, and timing of cold exposure for maximizing brown fat activation and weight loss have not been established. How different cold exposure methods compare in terms of fat loss and metabolic health outcomes is still under investigation.