published in the journal Obesity Reviews examines the link between reduced exposure to the cold and obesity in the UK and US.
We Burn More Calories When Cold
Historically, humans have lived in cold climates where they had to endure bitter cold for extended periods. Our body must burn calories at a much higher level to keep us warm during these times, and the increased metabolism helps to prevent overweight and obesity. This study review attempts to explain that seasonal cold helps to regulate energy balance and can help maintain normal body weight on a population level.
Indoor Temperatures Have Increased Over the Past Several Decades
The net effect is more calories burned for a longer period of time and this translates into lower body weight. Researchers have found that we experience a much smaller range of temperature variation than we did just 30 years ago. While this may not fully explain the skyrocketing overweight and obesity rates now seen across the US and UK, it does provide an important clue to how our environment can impact our ability to maintain a normal weight.
External Temperature Can Modify Our Fat Structure
Over the past decade, medical researchers have gained a much better understanding about the two distinctly different types of adipose or fat cells that we accumulate. White fat is metabolically active tissue that accumulates most commonly around the hips and mid-section of the body. Excess amounts of white fat are associated with inflammation, metabolic disease, heart disease and cancer.
Brown fat is a thermally active type of tissue that actually burns calories for energy and is associated with a higher metabolic rate and lower weight range. Researchers from the Obesity Reviews study found that when people spend more time in a climate controlled environment they produce less brown fat and metabolize fewer calories at rest. This was found to result in a tendency to gain weight, especially when coupled with a sedentary lifestyle.
The researchers concluded "Research into the environmental drivers behind obesity, rather then the genetic ones, has tended to focus on diet and exercise -- which are undoubtedly the major contributors. However, it is possible that other environmental factors, such as winter indoor temperatures, may also have a contributing role. This research therefore raises the possibility for new public health strategies to address the obesity epidemic." The bottom line is to carefully control calories and remain physically active. Be mindful that external environmental factors also contribute to your ability to successfully lose weight.