An experiment carried out by researchers shows that people who exercise at high intensity in the cold benefit from a better oxidation of lipids, the technical term for fat burning.
Wintertime means dark and cold days. So it's hard to find the motivation for your weekly outdoor workouts, but a study conducted by researchers at Laurentian University in Canada gives a good reason to put on your sneakers and go for a run in the cold. Published in the Journal of Applied Physiology, the study suggests that exercising at temperatures close to 0°C could burn more fat than normal, at least for high-intensity interval training (HIIT). It turns out that high-intensity exercise in cold weather increases lipid oxidation by a factor of three compared to normal temperatures.
Regular physical activity improves the metabolism of the nutrients consumed and helps regulate the levels of lipids (fats) in the blood. Previous research has shown that high-intensity interval training is better for fat burning than continuous moderate-intensity exercise. In the study, 11 overweight adult volunteers participated in two high-intensity exercise sessions one week apart. In the two sessions, they performed 10 one-minute sprints at 90% effort followed by a 90-second recovery period at 30% effort. At the end of the sprint session, volunteers were allowed to cool down by cycling or walking.
Increased fat burning in the cold
During one session, the ambient temperature was "thermoneutral" at about 21°C while for the other session the temperature was 0°C. "This is the first study to study the effects of cold ambient temperatures on metabolism during high-intensity interval exercise, as well as on metabolism the next day," write the researchers in their paper. They measured participants' body temperature and heart rate, the amount of oxygen supplied to the quadriceps muscles during the two sessions. Levels of glucose (blood sugar), oxygen and carbon dioxide, as well as gas exchange rates were also recorded.
After each workout, the volunteers ate a nutritious bar rich in protein and carbohydrates before going to sleep. The next morning, the team offered them a high-fat breakfast, after which blood samples were taken to measure insulin, glucose and triglyceride levels, to re-determine lipid oxidation rates and to see if the benefits of the previous night had been maintained. "The study found that high-intensity exercise in the cold increased lipid oxidation by 358% during exercise compared to a high-intensity session in a thermoneutral environment," the researchers added.
The metabolism does not react differently the next day.
However, there was no substantial difference after breakfast the next morning (the postprandial period): longer-term metabolic responses after eating this meal, including blood sugar control, fat burning and triglyceride levels, did not change much after the cold workout. The scientists therefore state that "the addition of a cold stimulus was less favourable for postprandial metabolic responses the next day. The glycemic response (change in blood glucose levels after eating) was even better after exercise in a thermoneutral environment, in terms of post-breakfast readings.
"Acute benefits are present during high-intensity interval training in the cold, but postprandial metabolic responses are less favorable in this context," the researchers point out. With so few volunteers and only a few sessions of HIIT, it is too early to draw any radical conclusions, but they feel that this is an interesting starting point to examine how ambient temperature can affect fat burning during periods of intense exercise. They conclude that no matter how much physical activity is done, it is essential for staying healthy and reducing the risk of chronic disease.
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