[Video version] Can the cold wave that makes you shiver burn fat and help you lose weight? Research: Low temperature promotes irisin secretion and helps burn brown fat

The cold wave is coming again, and it’s as cold as frozen sweet potatoes, making people shiver. They can’t help but want to hide in the warm bed as soon as possible to keep the body warm. However, some people say that being in cold weather can burn more fat and help lose weight. Is this true? Foreign studies have pointed out that exercising in a cold environment may induce the production of irisin in the human body, which is like turning on the engine that burns brown fat, thereby helping to burn more fat in the body!

Study: Irisin can activate white fat burning

What is Irisin? Irisin is a muscle hormone (Myokine) in the human body. It comes from the FNDC5 gene. When skeletal muscle exercise occurs, it will stimulate the FNDC5 gene to translate the FNDC5 protein and hydrolyze it to produce irisin, which is secreted into the circulatory system. Irisin is a type of protein. Previous experiments on mice have shown that irisin can drive white fat cells, which are originally responsible for storing energy, to transform into brown fat cells that help burn fat, a process known as "browning." The researchers conducted further studies to understand whether cold exposure is an incoming signal that initiates irisin secretion.

According to a study conducted by Dr. Paul Lee, MD, from the Department of Diabetes Endocrinology and Obesity at the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, USA, and published in the journal Cell Metabolism, shivering in a cold environment stimulates the expression of the FNDC5 gene in the human body, thereby increasing the secretion of irisin; and even without a shivering response, it can also drive fat cells to secrete another hormone, achieving the effect of burning brown fat in a cold environment.

What is brown fat? There are three types of fat cells in the human body: white fat, beige fat and brown fat. Brown fat cells are brown in color because they are rich in mitochondria. They also contain a large amount of uncoupling protein 1 (UCP1), which accelerates the rate at which cells break down fatty acids and generates heat. Once fully activated, they can burn about 10% to 20% of the basal metabolic rate every day.

Study: Shivering promotes irisin secretion in the body

In order to determine the impact of low temperature on the changes in irisin, after the subjects were exposed to cold, it was found that the skin temperature of all subjects dropped significantly, but the core temperature was maintained. It was also found that the temperature in the areas from arms to hands, skin to core, and clavicle to chest all increased, among which the temperature increase from clavicle to chest was the most obvious. In addition, the researchers used surface electromyography (EMG) to quantify the subjects' shivering performance during the experiment. The results showed that 7 of the subjects shivered when exposed to cold, and the irisin values ​​measured in the serum of these 7 subjects were positively correlated with shivering activity.

Irisin can drive the transformation of white fat cells, which are originally only responsible for storing energy, into brown fat cells that help burn fat, which is the so-called "browning".

Study: Endurance exercise stimulates irisin secretion more than aerobic exercise

The experiment was conducted by comparing 10 healthy adults, including 4 women aged between 27±5 years, with a body mass index (BMI) between 22±2 (kg/m2) and body fat (BF) between 24%±9%, to observe the secretion of irisin in the body under maximal and submaximal exercise and staged progressive cold exposure (27°C–12°C).

Two forms of standard exercise testing were used. The first was to test the subjects' maximum oxygen uptake (VO2max) during aerobic exercise. In the second stage, the subjects were required to exercise for 1 hour at 40% of their maximum oxygen uptake (40% VO2max) to simulate endurance exercise. Maximum Oxygen Consumption (VO2max) refers to the maximum amount of oxygen (milliliter, ml) that the human body can absorb per minute (min) per kilogram (kg) of body weight. Maximum oxygen uptake = cardiac output × arteriovenous oxygen difference, which is widely used as an indicator to measure cardiopulmonary endurance.

The results showed that the increase in irisin was greater during submaximal exercise compared to maximal exercise, suggesting that endurance exercise may have a stronger stimulatory effect on irisin secretion. The researchers believe that exercise may be a form of shivering mimic, so exercising or shivering in a cold environment can promote the secretion of irisin in the body.

The above experimental results show that shivering or exercising under cold exposure can stimulate the production of irisin in the body, thereby helping to start the burning of brown fat. However, this study also found that even without shivering, cold exposure will promote the expression of fibroblast growth factor FGF21 (fibroblast growth factor 21). Fibroblast growth factor FGF21 is a member of the fibroblast growth factor family and is a secretory protein that regulates the body's metabolic function. When induced by a cold environment, it will also promote the browning of white fat, which is the so-called "browning", thereby helping to burn brown fat.

The researchers believe that exercise may be a form of shivering mimic, so exercising or shivering in a cold environment can promote the secretion of irisin in the body.

Although exercising in the cold seems to promote the burning of brown fat in the body and increase the fat burning effect, before exercising in winter, you need to pay attention to warming up before exercise and prepare sports equipment, etc., in order to enhance the body's fat burning ability in the safest condition. The National Health Administration specifically reminds you of the following four tips for winter exercise:

【4 tips for winter sports】

1. Avoid dressing too warmly:

When exercising in winter, it is recommended to dress in layers, which is not only easy to put on and take off, but also helps to adapt to the environment with large temperature difference between inside and outside. In addition, since sweat during exercise can easily make clothes damp, you should try to avoid wearing sweat-absorbent cotton clothes to prevent colds.

2. Pay attention to warm-up exercises:

You should warm up before exercising, at least to the point where your heart rate increases and you sweat a little, to avoid sports injuries.

3. Do not drink alcoholic beverages:

Since drinking alcohol can cause blood vessels to dilate, blood pressure to drop, and heat dissipation to increase, which can easily lead to hypothermia, you should avoid drinking alcoholic beverages during exercise.

4. Note to patients with cardiovascular diseases:

People with asthma, cardiovascular disease, chronic bronchitis or Raynaud's disease should avoid exercising when cold waves hit. If they really must exercise in cold weather, it is recommended to discuss the appropriate exercise method and the medications that should be prepared when exercising with a doctor.