As it has been a trend for years, many believe the claim that exercising in cold or hot temperatures will cause you to burn more calories, leading to weight loss. Although many believe this, it is not actually true nor an efficient way to lose weight.
First, let me take you through how humans burn calories. The most common way you burn calories is by your metabolism. According to the Mayo Clinic, “metabolism is the process by which your body converts what you eat and drink into energy. During this complex biochemical process, calories in food and beverages are combined with oxygen to release the energy your body needs to function.” Metabolism can also be classified as your basal metabolic rate, or how many calories your body uses to carry out these functions. The basal metabolic rate makes up about 60 to 80 percent of your total energy expenditure and calorie loss. In addition to your metabolism, a portion of your energy expenditure and therefore loss in calories comes from thermogenesis: the way in which the body produces heat. Thermogenesis makes up 10% of total energy expenditure, leaving only 10-30% for physical activity (which, in reality, is not a lot).
In terms of that last 10-30%, the body burns the remaining calories by shivering (if cold) or by exercising. Shivering and exercise are viewed as the same inside of the body as they both trigger the activation of what is called brown fat or brown adipose tissue. When you shiver, your muscles involuntarily contract to generate warmth to regulate homeostasis but it also triggers “muscles to secrete a hormone that stimulates energy use in brown fat cells” (according to the National Institute of Health). The same thing happens when you exercise! In another example, brown fat helps infants who don’t know how to shiver yet regulate their body temperature.
While brown fat burns calories to generate heat, something called white fat stores calories as heat / insulation to keep you warm. As you can assume, It is better to have more brown fat than white fat as large amounts of white fat, and this insulation, can lead to obesity. This is because white fat stores energy in large lipid droplets throughout the body. On the other hand, brown fat contains smaller lipid droplets and higher amounts of mitochondria. This increase in mitochondria causes an increase in ATP or energy production and therefore increase in energy expenditure and calorie loss.
So how is this related to energy expenditure and calorie burning, you ask? Many people believe that you can burn more calories in the cold because of this brown fat. Although this is true, you need at least 2 hours in 66 degrees fahrenheit (or lower temperature) in order to see the extreme effects of the body activating the brown fat and burning more calories. On the other hand, many believe that you will burn more calories in the heat (or hot conditions) because sweating more must mean your body is working harder and losing more calories, right? This is not always the case – releasing more sweat doesn’t always mean you are releasing more energy and losing more calories. Rather, in the case of very hot conditions, like hot yoga for example, the sweat you are releasing only causes you to lose more water, not calories.
There are pros and cons to any type of exercise, but ultimately choosing to work out in hot or cold conditions to promote weight loss, may do more harm for you than good, especially if you are new to the exercise scene as your body may not react well to these temperatures. To promote weight loss, you must be in a calorie deficit – burning more calories than you are in consuming. This is the best and really the only way to lose weight (along with exercise).