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Central Heating May Be Making Us Fat May 26, 2011

Posted by ADAM PARTNERS in Possible causes of Obesity Epidemic in USA.
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Americans like to crank up the heat in the winter — and some scientists think it’s making us fat. Turn down the thermostat, they say, and you might lose a few pounds.

The link between ambient temperature and weight is not completely far-fetched. When we’re exposed to extreme cold, we shiver, an involuntary reaction that makes our skeletal muscles contract to generate heat, burning extra calories in the process.

And even in mildly cold conditions, like in a chilly room with the thermostat turned down to the lower 60s, people generate extra heat without shivering. The process, called non-shivering thermogenesis, may involve a substance called brown fat that adults carry in certain areas, like the upper back and side of the neck. Unlike regular fat, which stores excess energy and calories, brown fat acts like an internal furnace that consumes lots of calories, but it has to be activated first — and cold temperatures do that.

Now, in a provocative new paper, British researchers argue that rising indoor temperatures are contributing to obesity. The research team included scientists from several disciplines, including health psychologists, biologists and those who specialize in the effects of indoor environments.

The hypothesis was initially put forth several years ago in a paper listing 10 “putative contributors” to obesity, including environmental endocrine disruptors, pharmaceuticals that induce weight gain, sleep debt, older mothers having children and epigenetic changes, or environmental factors that influence the expression of our genes.

The newer paper, published this week in the journal Obesity Reviews, looked specifically at indoor temperatures. The researchers found that since central heating became commonplace in the 1960s, room temperatures have increased slowly but steadily in both the United States and Britain. In both countries, obesity has also been on the rise.

The average temperature of living rooms in Britain, around 64.9 degrees Fahrenheit in 1978, had risen to 70.3 degrees by 2008. Bedrooms, kept at 59 degrees in 1978, were up to 65.3 by 1996, the last year figures were available.

In the United States, living rooms have long been heated to just over 70 degrees in the winter, at least when the house is occupied. Bedroom temperatures continue to rise and were up to 68 as of 2005, from 66.7 in 1987.

“What’s particularly noticeable is that people are heating the whole of their house,” said Fiona Johnson, a research fellow at University College London and the paper’s lead author. “In the past they would heat the main living areas, and the bedrooms might be cold at night.” That means people no longer have to adjust to different temperatures as they move through the house.

In addition, most people get around town in heated cars, instead of walking, and children spend less time playing outdoors.

All this time spent in toasty interiors may be affecting the levels of brown fat we carry, Dr. Johnson said. “It’s kind of ‘use it or lose it,’ ” she said. “If you’re not exposed to cold, you’re going to lose your brown fat, and your ability to burn energy will be affected. But you can get it back.”

While we all start out with substantial amounts of brown fat as babies, “it gradually decreases over the life course,” she said. “But if it is needed — if we’re regularly exposed to cold — the body can actually generate more brown fat.”

That is not to say exposure to cold is a major driver of obesity: overeating and lack of exercise are the main causes.

But could lowering the thermostat make a notable difference in people’s weight?

Dr. C. Ronald Kahn, a Harvard Medical School professor who does research on brown fat, says it might actually help with weight control over time, provided people stick with it.

“When we put people in a 60-degree room, they increase their energy expenditure by 100 or 200 calories a day if they’re in light clothing,” like hospital scrubs, he said. “They’re not shivering. They activate their brown fat.”

Over a period of several weeks, they will have burned an extra 3,500 calories, which translates into the loss of one pound. Wearing a sweater will dilute the effect.

The problem, Dr. Kahn said, is that “most people won’t stay at that temperature for very long.”

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Comments»

1. Know Who’s Making You Fat? Your House! Really. « Alternative Health Answers - May 31, 2011

[…] Central Heating May Be Making Us Fat (ingunter.wordpress.com) […]


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