The obesity epidemic may be due to insufficient sleep and too comfortable indoor temperature, as much as a sedentary lifestyle and aggressive marketing of fast food. It emerges from a new study where an American research group has reviewed the literature in the field. They point to 10 different causes that can be as important as the two most common scapegoats.
The study paints a more complex picture of the obesity epidemic, where there are many factors, and it is not clear which factors are most important.
Almost a quarter of all Americans are overweight. As a rule, this is explained by too much sofa seating and too much bad food, as a result of aggressive marketing from the fast food industry. David Allison and the co-authors of the new study, on the other hand, say that the documentation for The Big Two is no better than the documentation for the other theories.
They describe the situation in the field of research as hegemony, where the two common explanations are accepted as established, and other important factors are not properly investigated.
The researchers believe the consequences could be well-meaning, but failed strategies to overcome obesity. The documentation for the two most common theories is largely based on clues, and depends on correlations rather than epidemiological data at the individual level or randomized experiments, they write.
We outline the documentation for 10 other factors where the documentation is also based on clues, but in many cases are at least as interesting. We conclude that a disproportionate amount of attention has been paid to reduced physical activity and marketing methods for food, which has led to a neglect of other plausible mechanisms, the researchers write.
Here are the ten alternative explanations:
1) Lack of sleep: People sleep less, and several studies link sleep deprivation to weight gain.
2) Substances that create endocrine disorders: Industrially produced substances can create hormonal disorders that lead to obesity.
3) Indoor temperature: Better heating and air conditioning ensures that we burn fewer calories through sweating and freezing.
4) Fewer smokers: Smokers tend to weigh less than non-smokers, and people who quit smoking tend to quit. Cigarette smoking has declined in recent decades in the United States.
5) Medications: Several common medications cause weight gain.
6) Age and ethnicity of the population: Larger proportions of the American population are middle-aged, and a growing proportion has a Latin American background. These two population groups traditionally have a higher proportion of overweight people.
7) Older mothers: Women are getting older when they have children, and an older mother is a risk factor for developing obesity.
8) Genetic influence: Genetic influence can occur during pregnancy, or it can originate from two generations back – from the fetus that was in the womb to the grandmother. Thus, it is possible that the current obesity epidemic is related to environmental changes that affected previous generations.
9) Natural selection: Chubby people have more children than thin people.
10) Fat chooses fat: Obese people tend to be with someone with the same body type, and this can gradually make the population heavier.
The study has so far received a mixed reception. Some characterize it as creative and provocative. Others believe that it gives people with weight problems an excuse not to take care of their diet or move more.
Allison points out that the researchers do not suggest that people should stop taking their medication, start smoking or get hot in the summer sun.