Study: Obesity’s insulation trap

Two Simon Fraser University researchers are seeking 40 participants for a follow-up study to their preliminary discovery that obese people are prone to gaining weight in mild cold weather.

In these studies obesity is defined as having a body mass index (BMI)—an estimation of body fat content based on weight and height—of more than 30 kilograms per metre squared.

In their preliminary studies, Mathew White, an SFU associate professor of biomedical physiology and kinesiology, and Andrew McMillan, White's graduate student, compared the metabolic responses of obese and thin people in cold water and/or air.

Their subjects, primarily obese or thin men aged 19 to 45, were exposed to different mildly cold water and air conditions for varying periods of time. The researchers' results support that obese people display adaptive thermogenesis.

The term refers to a person's reduced metabolic response to physical stresses, such as during mild to moderate cold-water immersion or cold-air exposure.

"For example," says White, "a tall thin and lean person who is 1.78 metres tall and weighs 54.4 kilograms has a greater metabolic response standing in a cold room relative to an obese individual who is 1.65 metres tall and weighs 113 kilograms. The thin individual will shiver intensely, expending more calories in the cold room in an effort to warm up. The obese individual may have little or no metabolic response and remain at a resting rate of expenditure."

The balance between energy taken in and energy expended largely determines a person's body weight and obesity. Obesity is almost epidemic and accounted for an estimated $4.3 billion in disease-related health care costs in Canada in 2005.

"Our preliminary finding that individuals with higher BMI cool more slowly and have reduced metabolic responses compared to thinner people in cold conditions is relevant to weight gain and obesity's health consequences," explains White.

"Individuals, once obese, appear to live in an insulation trap. Day-to-day physical stresses such as mild temperature cooling invoke less of a metabolic response than in their counterparts of normal body weight. This means cold weather can predispose already overweight and obese individuals to more weight gain and the associated medical conditions collectively known as the metabolic syndrome."

For the follow up study, which has now been underway for a year, the researchers are currently seeking more participants to fill out their need for 20 control individuals and 20 people with a high BMI. Because their preliminary findings were based on mainly obese males, aged 19 to 45, they are keenly interested in recruiting participants with this profile but anyone can apply.

Provided by Simon Fraser University