If you ask anyone about why obesity turned into an epidemy, he will surely answer that it has to be with the amount you eat and the amount you burn. Almost everyone has to make some effort to stay thin.

This explanation is in conicidence with common sense, and till now has guided the efforts to come to the root of this epidemy of obesity. Nevertheless, nowadays many people believe that something else must have changed in our environment to precipitate such a dramatic increase of obesity in the last 40 years.
An article signed by 20 experts in the topic, published in the International Journal of Obesity, advances on the most commendable 10 alternatives to explain this phenomenon, since the fact of being surrounded by an “obesity” environment – where you can easily find cheap food rich in fats, and sedentarism seem to be the accepted policy - cannot explain thoroughly this international phenomenon.

These are the hypotheses:

1. Insufficient sleep

Those that sleep less than seven hours in night are in the habit of having a corporal mass (BMI, Body Mass Index) superior to that of the people who sleeps more, according to the information compiled by the National American Survey of Health and Nutrition. In a similar way, the Study of the Nurses, which followed 68.000 North American women for 16 years, thought that those who were sleeping in average five hours a night gained more weight than those that were sleeping six, which in turn put more weight that those that were sleeping seven. Two recent studies, one in Canada and other one in Germany, show that the duration of sleep and the weight are related also in children.
The lack of dream would alter the metabolism. Leptin, an hormone in charge to indicate the satiety, falls down, whereas the Grelin, which stimulates the hunger, rises. In men allowed to sleep only 4 hours a night for two consecutive days, the levels of Leptin fell down 18 per cent, whereas Grelin increased 28 per cent.

2. Climate Control

Human beings, as all warm blooded animals, prune to mantain our corporal temperature in a steady range. Most of us prefer a tempearature of about 25 ºC.

Could it be that air conditioning the heating do a difference in our weight?
Regretably, evidence turns the answer into a yes. Different studies show that when the temperature is agreeable we use less energy. A study, where a group of women wewre exposed to 27 °C versus 22 °C, the difference was of about a megajoule (239 kilocalories) per day. This amount of energy corresponds to 27 grams of corporal fat.

3. We smoke less

Bad news: smokers tend to be thinner than the rest of us, the healthy ones. Quitting cigarette makes us gain weight, and till now nowone has discovered why. Probably it has something that to do with the fact that nicotine is an apetite suppresser, and seems to increase our metabolic index. In agreement with the information obtained by the National American Survey of Health and Nutrition in 1991, people who had stopped smoking in the previous decade were tending to have more overweight than those who were smoking or who had never smoked. For example, near half of the men that had stopped smoking had overweight, in comparison with 37 per cent of the non smokers and only 28 per cent of the smokers.
This does not mean that to stop smoking is a threat against public health, not at all. The cigarette is so dangerous that it would be necessary to raise 45 kilos to justify the fact of continuing smoking.

4. Prenatal factors

The possibilities of turning into fat men can be decided largely before we are born. Children from obese mothers - specially if they had developed geatational diabetes - have more possibilities of turning themselves into obese. While this can could all be atribuited to genetics , there also exists evidence of an “intrauterin programming”. Scions of mice fed on a diet rich in fats during pregnancy have far more probabilities of becoming fat that those of identical mice, but fed on a normal diet. Strangly, this effect persists for two or three generations. The grandsons of the mice fed on a diet rich in fats become fat even if its own mother is fed normally.
In the other edge of the spectrum, we know from studies done in persons born during the Netherlands famine (that came as a result of the Second World war), that the restrictions of energy in the mother wound can lead to obesity with the pass of the years.

5. Fat man = Big Family

The heaviest people have more children. A study realized by Lee Ellis in the State University Minot, North Dakota, found a “small but very significant relation” between the BMI and the reproductive levels. Women with a normal or minor weight have in average 3,2 children, whereas those with overweight or directly obese, have an average of 3,5 children.
Having to many children increases the opportunities of weight gaining, and this could be explained with the lack of dream (to see above). Ellis also demonstrated that the BMI of people before they become parents is associated with the number of children they eventually have.

6. A bit older

Some groups of people simply are fatter than others. Surveys realized by the National American Center for the Statistics of Health found that it was about three times more likely that adults of between 40 and 79 years were fatter than the youngest people. Not Caucasian women also tend to locate in the same side of the spectrum: Mexican - American have 30 per cent more possibilities than the white ones of being obese, and the african-american carry this risk doubled.

7. More drugs

Nowadays, million of people take neuroleptics. Beyond its undoubted success for psychosis treatment, they have a disadvantage: Its users increase an average of four kilos in the first 10 week, and another four or five in the following year.
Neuroleptics are not the only class of drug that makes people gain weight: anticonvulsive for epilepsy treatment, antihypertensive for high blood pressure, protease inhibitors for AIDS treatment and diabetes medication, including insulin, they are all associated with an increase of weight. Beta blockers increases weight in an average of 1,2 kg, and having taken contraceptive pills for more than two years approximately a five kilos increase.

8. Pollution

We are exposed on a Daily basis to thousands of industrial chemists: pesticides, leaches, parfumes, plastics, resins and solvents, etc. We swallow them, inhale and absorb across our skin. There exists some evidence showing that low levels of some of these chemicals can drive to an increase of weight.
Some of these chemicals interfere with the correct strogen function. Numerous studies in animals and in human beings suggest that when strogens do not work correctly, adiposity increases.

9. Old mothers

An older mother seems to be a factor of independent risk in respect to obesity. The results of a study of growth and health realized by the National American Institute of the Heart, Lungs Blood shows that the possibilities of a child of becoming obese increase about 14 per cent every 5 extra years in the age of his mother, in spite of the fact that it is not well known why.
Michael Symonds of the University of Nottingham, United Kingdom, discovered that the lambs that were born of elderly sheeps were accumulating more weaved adiposly in the first year of life. Symonds also discovered that the first-born ones have more body fat than his smaller brothers. In the United States, in 1976, 9,6 per cent of the women of approximately 40 years had had only a son; in 2004 they were 17,4 per cent those that were in this situation. This combination of aged mothers and major amount of an only children can be contributing to the obesity epidemy.

10. I like you

In the same way in which people are joined in agreement with its aspect, it also happens in agreement with its size. In a study of 1341 Canadian families published in 1999, Peter Katzmarzyk, of the University York, in Toronto, discovered that there is a small but significant relation between husband and wife In respect to the BMI and also in the measurement of the cutaneous plaits, that cannot be attributed to the fact of living together.
Marrying someone of similar structure cannot be considered the reason of the increase of the obesity, combined with other things - particularly with the fact that the obesity is partly genetic, and that the heaviest people have more children - it amplifies the increase of thhis epidemy due to other reasons.

By Alison Motluk

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