The World Health Organisation (WHO) last September warned that a billion people were overweight and obese, and the toll could rise to 1.5 billion by 2015, driven by low- and middle-income countries.Writing on Tuesday in the International Journal of Obesity, a team of US public-health experts caution against focussing obsessively on the "Big Two" -- a slower lifestyle and modern food marketing. "This has created a hegemony whereby the importance of the Big Two is accepted as established and other putative factors are not seriously explored," they say. "The result may be well-intentioned but ill-founded proposals for reducing obesity rates."
They contend the evidence against junk food, supersize-me portions and high-calorie corn syrup is "equivocal and largely circumstantial" and offer some intriguing ideas of their own for other drivers of the obesity tsunami.
Hereupon follows a list of the possiblities for which there seems to be supporting evidence (all of which don't have anything to do with whether or not you, dear reader, are a lazy pig):
-- Industrial chemicals called endocrine disruptors that disturb metabolism, encouraging the formation of fat.
-- Giving up smoking: people who give up cigarettes very often gain weight.
-- Air conditioning, which establishes a comfortable temperature zone. In temperatures above this zone, people eat less. The rise in number of air-conditioned homes in the United States virtually mirrors the increase in the US obesity rate.
-- Fat people marry other fat people. These individuals may be genetically vulnerable to obesity, a trait that could handed on to their children.
-- Sleep depriviation. University of Chicago researcher Esra Tasali notes that waistlines in modern societies started to expand when people started to sleep less. Today, the "sleep deficit" is about two hours per night compared with 40 years ago. To test this hypothesis, Tasali recruited a group of healthy young adults and divided them into three groups. One group had eight hours' sleep; another had their sleep regime extended to 12 hours; and the third was limited to only four hours. The sleep-deprived group swiftly developed cravings for high-calorie sweets, and their metabolisms were akin to those of diabetics.
-- Viral infection. At least 10 different pathogens are known to cause obesity in animals, causing dramatic changes to the metabolic system so that more energy gets converted into fat.
Nikhil Dhurandhar of the Pennington Biomedical Research Center at Louisiana State University believes that something similar may happen among humans exposed to cousins of the common cold. He tested the stored blood of 500 Americans and found that 30 percent of obese people had antibodies for Ad-36, an adenovirus which causes coughing, sneezing and cold-like symptoms. Only 11 percent of people of normal body weight had this telltale of Ad-36 infection.