University of Alabama biostatistician David Allison and 19 other scientists from Canada, Italy and the United States examined more than 100 studies to determine the top 10 contributors to obesity other than diet and exercise.
The scientists found many studies connecting sleep deprivation to weight gain, and the average amount of sleep is dropping worldwide. The smoking population is also dwindling, and although its health detriments are many and proven, smoking is a successful appetite suppressant. Some modern processed foods may also contribute; they contain endocrine disruptors, which are substances that may alter fats in the body. They found many medicines can contribute to weight gain as well. Surprisingly, some modern-day conveniences can worsen weight gain; air conditioners preclude weight loss from sweating, and heaters mean weight is not lost from shivering.
The group also found that overweight people tend to procreate with other overweight people in a phenomenon that Allison refers to as "like mating with like," or "Assortative mating." More women are also having children later in life, and older mothers tend to have heavier children. In addition, genetic influences during pregnancy can affect a child's weight after birth.
Overweight people have also outlived malnourished people throughout history, so natural selection may even play a role. The population is also changing, as more middle aged people and Hispanics are showing increased obesity rates.
Allison said the study did not suggest that people should make it a priority to alter the above factors, noting that he and the other scientists would never recommend smoking as a weight loss aid, for example. Weill-Cornell Medical School nutrition export Dr. Louis Aronne said that people should not suddenly stop their medication to prevent weight gain, but that they could discuss possible alternatives with their doctors.
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