Air-con and lack of sleep promote obesity
12:56 27 June 2006
NewScientist.com news service
Kurt Kleiner
Obesity is just as likely to be caused by lack of sleep and too much air-conditioning as it is by a sedentary lifestyle and aggressive marketing by the food industry, according to a research article that challenges the conventional wisdom.
David Allison, an obesity researcher at the University of Alabama at Birmingham, US, and colleagues have published a paper questioning the importance of what they call the "Big Two" obesity factors: overeating as a result of junk food marketing and lack of exercise.
In the US the proportion of the population defined as obese increased by 60% between 1991 and 2000, so that now almost a quarter of all Americans are obese. Most researchers tend to attribute the increase to a more sedentary lifestyle and overeating driven partly by aggressive corporate food marketing. But Allison says that the evidence for the Big Two is far from conclusive.
"What seems intuitively to be right is not always right. This might be an example where the rush to judgment may have negative effects," Allison says.
Physical education
For example, some studies have found no correlation between the number of hours children spend in school physical education classes and the proportion who are overweight. Others have failed to find a connection between being overweight and a proximity to fast food restaurants or consumption of soft drinks.
The researchers drew up a list of 10 factors that might have as much or more to do with increasing waistlines as the Big Two. For instance, they point out that studies show that people who do not get enough sleep have increased appetites. Notably the amount of sleep an average US adult gets has decreased from nine hours to seven hours in the last several decades.
Heating and air conditioning might also be to blame. When people and animals go above or below a "thermoneutral" ambient temperature, they lose weight - if it is too cold they burn fat to stay warm, and if too hot their appetites decrease. But studies show that people are keeping their houses warmer in the winter and cooler in the summer than they did a few decades ago, so these natural influences on weight are negated.
Other possibilities include the decrease in the number of people who smoke - which suppresses appetite - environmental endocrine disruptors, an ageing population, and an increase in babies born to older women - which are more likely to be obese. Another possibility is that overweight people are more likely to marry one another and give birth to children genetically predisposed to be overweight themselves.
Barbara Rolls, an obesity researcher at Penn State University in University Park, US, says that the paper is provocative, but it makes a good point that obesity probably has many contributing causes.
"In the end, though, it boils down to what you eat and how much you move. I still don't think we should lose our focus on those variables," she says.
Journal reference: International Journal of Obesity (DOI:10.1038/sj.ijo.0803326)
12:56 27 June 2006
NewScientist.com news service
Kurt Kleiner
Obesity is just as likely to be caused by lack of sleep and too much air-conditioning as it is by a sedentary lifestyle and aggressive marketing by the food industry, according to a research article that challenges the conventional wisdom.
David Allison, an obesity researcher at the University of Alabama at Birmingham, US, and colleagues have published a paper questioning the importance of what they call the "Big Two" obesity factors: overeating as a result of junk food marketing and lack of exercise.
In the US the proportion of the population defined as obese increased by 60% between 1991 and 2000, so that now almost a quarter of all Americans are obese. Most researchers tend to attribute the increase to a more sedentary lifestyle and overeating driven partly by aggressive corporate food marketing. But Allison says that the evidence for the Big Two is far from conclusive.
"What seems intuitively to be right is not always right. This might be an example where the rush to judgment may have negative effects," Allison says.
Physical education
For example, some studies have found no correlation between the number of hours children spend in school physical education classes and the proportion who are overweight. Others have failed to find a connection between being overweight and a proximity to fast food restaurants or consumption of soft drinks.
The researchers drew up a list of 10 factors that might have as much or more to do with increasing waistlines as the Big Two. For instance, they point out that studies show that people who do not get enough sleep have increased appetites. Notably the amount of sleep an average US adult gets has decreased from nine hours to seven hours in the last several decades.
Heating and air conditioning might also be to blame. When people and animals go above or below a "thermoneutral" ambient temperature, they lose weight - if it is too cold they burn fat to stay warm, and if too hot their appetites decrease. But studies show that people are keeping their houses warmer in the winter and cooler in the summer than they did a few decades ago, so these natural influences on weight are negated.
Other possibilities include the decrease in the number of people who smoke - which suppresses appetite - environmental endocrine disruptors, an ageing population, and an increase in babies born to older women - which are more likely to be obese. Another possibility is that overweight people are more likely to marry one another and give birth to children genetically predisposed to be overweight themselves.
Barbara Rolls, an obesity researcher at Penn State University in University Park, US, says that the paper is provocative, but it makes a good point that obesity probably has many contributing causes.
"In the end, though, it boils down to what you eat and how much you move. I still don't think we should lose our focus on those variables," she says.
Journal reference: International Journal of Obesity (DOI:10.1038/sj.ijo.0803326)
