Wearing an ice vest for two hours every morning for six weeks led to a loss of nearly a kilogram of body fat, according to researchers who presented their findings at the European Congress on Obesity in Istanbul.
The study, conducted by the University of Nottingham and the Leiden University Medical Center (LUMC) in the Netherlands, involved 47 adults with overweight or obesity. Half of the participants were given an ice vest and a waist wrap to wear for two hours each day while continuing their normal routines. The other half acted as a control group. By the end of the six weeks, those using the vest had lost an average of 0.9kg (2lb), almost entirely from body fat, while the control group gained 0.6kg (1.3lb).
How the ice vest method works
The vests and waist wraps were worn on top of a thin T-shirt and contained gel-filled cooling packs that had been kept overnight in a freezer. They maintained a steady temperature of 15°C throughout the two-hour exposure period. Dr Mariëtte Boon, the lead researcher from LUMC, described the work as “one of the first studies looking at the impact of cold exposure over a prolonged period of time, involving people with overweight and obesity.” She added that vests like these “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.”
The researchers stressed that the cold exposure method is not intended to replace diet or exercise but to complement them. The study, jointly funded by the Dutch Heart Foundation and the British Heart Foundation, aimed to test whether regular, tolerable cold exposure could produce measurable changes in body composition.
The science behind brown fat activation
The fat loss observed in the study is thought to be driven by the activation of brown adipose tissue (BAT), commonly known as brown fat. Unlike white fat, which stores energy, brown fat is metabolically active and burns energy to generate heat — a process called thermogenesis. Cold temperatures are the primary trigger for this response. When the body is exposed to cold, brown fat cells break down stored body fat and convert it into heat to maintain core temperature.
Professor Helen Budge, co-author of the study from the University of Nottingham, explained: “Daily cold exposure activates brown fat, which uses body fat stores to produce heat.” The University of Nottingham has been at the forefront of research into managing brown fat through nutrition, exercise, and environmental interventions, using techniques such as thermal imaging to assess BAT activity. Dr Boon is an international expert on brown adipose tissue biology and has studied pharmacological strategies to enhance BAT activity and energy expenditure.
The researchers believe that regular cold exposure may also train brown fat to become more active over time. “It is possible that wearing a cooling vest trains brown fat to be more active and has a healthy effect on lipids, glucose and inflammation in the body,” Professor Budge said. “All those things are preventative in cardiovascular disease.” Studies have shown that individuals with active brown fat have lower arterial inflammation, improved insulin sensitivity, and better blood lipid profiles, including healthier levels of triglycerides and HDL cholesterol. The activation of brown fat has also been linked to a reduced risk of cardiovascular disease.
Prolonged exposure to mild cold — around 19°C — has been shown in other research to not only activate brown fat but also to trigger the “browning” of white fat cells, converting them into beige cells that behave like brown fat. In the six-week trial, the consistent daily cold stimulus appeared sufficient to drive the fat loss seen in the vest-wearing group.
Cold showers and future research directions
The same research team is now investigating whether other forms of regular cold exposure produce similar effects. A separate study involving 34 women in the Netherlands is testing whether daily cold showers can also promote fat loss. Half of the women will set their shower to the coldest possible setting for 90 seconds each morning. “It is our hypothesis that cold showers and cold swimming could have the same effect,” Professor Budge said, though she cautioned that cold swimming is not directly comparable because “there are lots of other things at play such as cold shock – jumping into a lake would have other effects on the body.”
Dr Boon acknowledged the differences in exposure duration and intensity. “The cooling vest is a much longer period of exposure than the shower,” she said. “But on the other hand the cold shower is much colder. We will have to see if it has an impact on weight loss.”
Some research indicates that a brief cold shower can stimulate thermogenesis and increase daily energy expenditure by roughly 100–200 kilocalories, but there is currently no strong evidence that such short exposures alone produce clinically significant weight loss. Any temporary metabolic boost tends to fade once the body warms up. Cold water immersion, including ice baths and cold swimming, has been shown to activate brown fat cells but may also stimulate appetite, potentially leading to a net positive energy balance if calorie intake is not controlled.
The authors are continuing their investigations, jointly funded by the Dutch Heart Foundation and the British Heart Foundation, into whether other forms of regular cold exposure could reduce obesity, inflammation, and prevent heart disease. Longer-term studies are needed to understand the sustained impact of regular cold exposure on weight management and overall health, and the effects can vary between individuals. Although generally considered safe, cold exposure carries risks for vulnerable populations.
“We hope people can find a method of cold exposure that works for them and fits into their daily routine,” Dr Boon said.