A growing number of people are unable to shed those extra pounds despite strict diet regimes and long hours of workout. Evidence shows that the toxins in the environment could be playing the spoilsport. They modify the body’s physiology and make it difficult to lose weight. While the West is waking up to the complex linkages between chemicals and obesity, realisation is yet to dawn on doctors and researchers in India. Vibha Varshney, Dinsa Sachan and Sonal Matharu report on the new trigger for obesity and the way out
The new obesity
Obesity has just slipped out of the grasp of mathematical logic: if one burns as many calories as one consumes, one will not gain weight. Today it is easy to spot people in jogging parks, aerobic centres and gymnasiums who defy this logic. Take Sundar Rao of Mumbai who weighs 89 kg. He has been trying hard to shed the extra pounds for the past 15 years. A 53-year-old chartered accountant, he religiously takes out an hour from his busy schedule for exercising and has tried all possible diet regimes he could dig out of the massive literature and studies done on weight loss. Rao has cut down on carbohydrates, increased protein intake and reduced the amount of fat he consumes. Eating out is curtailed, fruits have been added to the plate and packaged foods kicked out, but to no avail. For his height of 170 centimetres, he is 19 kg overweight; worse, he continues to gain weight.
Forty-year-old Sapna Vashista of Delhi has a similar problem. For the past six years, she has maintained a strict diet regime. One hour of yoga or aerobics and evening walks are part of her daily routine. A part-time fashion designer and mother of two, she does most of the housework. Still her weight does not dip below 72 kg. For her height of 165 centimetres, Vashista should not weigh more than 63 kg.
Both Vashista and Rao share the fate of many people who even after hours of slogging on the treadmill and giving a miss to their favourite food are unable to shed those extra pounds. The World Health Statistics released in May by WHO also points to the growing trouble. It shows obesity has doubled across the world between 1980 and 2008. Health experts say overeating and junk food are the biggest reasons behind the rise in obesity world over, but they cannot explain why some people are unable to lose weight when they control these habits.
Moreover, food could hardly be blamed for the increase in weight of babies below six months. Data from a research by Harvard Medical School shows the percentage of overweight infants has nearly doubled from 3.4 to 5.9 between 1980 and 2001 in the US.
Baffled researchers who set out to find the reasons say the toxins in the environment, microbes and rise in temperature also play a role in making people fat. Specifically, exposure to certain toxins, such as pesticides, emissions from vehicles and the material that the plastic bottle is made of, can lead to weight gain. Epidemiological studies suggest everyone, including those not yet born, are at risk. Most such studies have been done in the US.
For instance, a study in the US on pregnant women in New York City showed that women exposed to higher concentrations of polycyclic aromatic hydrocarbons, or PAHs, from vehicular and industrial exhaust and smoke from cigarettes, were more than twice as likely to have children who were obese by the age of seven. The study was conducted by researchers from Mailman School of Public Health at Columbia University.
| HISTORY OF OBESOGENS
There were studies as far back as in the 1970s to show that low-dose chemical exposures were associated with weight gain in animals. She published the results in the Journal of Alternative and Complementary Medicine in 2002. The paper was noticed by many researchers who had observed similar phenomenon in their lab animals. They initiated studies to observe the effect of the toxins on body’s metabolism. Retha Newbold of the National Institute of Environmental Health Sciences (NIEHS) in the US tested Diethylstilbestrol (DES), used in drugs, on mice.
They were treated with 0.001 mg/kg of DES and their weight was measured after four months. While the treated mice had average weight of 40.3 grams, those not exposed weighed 30.7 grams. By 2007, the evidence was so clear that a University of California scientist, Bruce Blumberg, gave these chemicals a name—obesogens.
“There are currently about 20 chemicals that have been shown to stimulate weight gain in rodents,” says Jerrold J Heindel, programme administrator at NIEHS. These chemicals are everywhere—soft drink cans, carpets to paper money. Exposure to them is unavoidable.
The National Health and Nutrition Examination Survey in the US shows similar results. When children between six and 19 years of age were tested for the presence of pesticide 2,5-dichlorophenol—commonly used in moth balls, and room and toilet deodorisers, and previously used as an insecticidal fumigant—it was found that obesity was directly proportional to the levels of the chemical in the blood. The study was published in Reviews on Environmental Health in 2011. Adults with higher levels of Bisphenol A (BPA)—commonly used in plastic bottles—were also found to be more prone to general and abdominal obesity by researchers of the Harvard School of Public Health in Boston. Till date, about 20 chemicals have been nailed for inducing weight gaining tendencies and many more may soon make it to the list. Based on their effect, the chemicals have been christened obesogens (see ‘History of obesogens’).
This does not mean diet regimes and treadmill are redundant. Whether obesogen exposure causes permanent changes in the body leading to obesity is currently under study in laboratories across the world, developmental biologist Bruce Blumberg says. Epidemiological studies give only indications. Direct studies are available only on animals. In his lab in the University of California, Irvine, US, Blumberg is analysing the obesogenic impact of a chemical, tributyltin (TBT), on mice. TBT is a biocide that is used in paints in ships to prevent the growth of algae on the hulls. It has now been banned because it leaches into the sea and affects marine life. Blumberg says, “Prenatal exposure to TBT produces irreversible effects in mice.” They get fatter despite a normal diet because TBT alters their metabolism. “So if you were exposed at a sensitive time during your life such that you have more, larger fat cells and stem cells that are predisposed to become fat cells, you will have to fight a lifelong battle against weight gain.”
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