Plastic could make you obese


The global obesity epidemic is worsening, particularly among children, with obesity rates increasing over the past decade and moving towards younger ages. In the United States, about 40% of today’s high school students were overweight when they started high school. Globally, the incidence of obesity has tripled since the 1970s, and one billion people are expected to be obese by 2030.

The consequences are serious, as obesity is closely linked to high blood pressure, diabetes, heart disease and other serious health problems. Despite the magnitude of the problem, there is still no consensus on the cause, although scientists recognize many contributing factors, including genetics, stress, viruses and changes in sleep patterns. Of course, the popularity of heavily processed foods – high in sugar, salt and fat – has also played a role, particularly in Western countries, where people on average consume more calories per day today than there were. is 50 years old. Even so, recent scientific reviews conclude that much of the huge increase in obesity worldwide over the past four decades remains unexplained.

An emerging view among scientists is that a major overlooked component in obesity is almost certainly our environment – in particular, the ubiquitous presence within it of chemicals which, even in very low doses, act to disrupt the normal functioning of human metabolism, upsetting the functioning of the organism. ability to regulate energy intake and expenditure.

Some of these chemicals, called “obesogens,” directly stimulate the production of specific cell types and fatty tissue associated with obesity. Unfortunately, these chemicals are used in many basic products of modern life, including plastic packaging, clothing and furniture, cosmetics, food additives, herbicides and pesticides.

Ten years ago the idea of ​​chemically induced obesity was something of a fringe hypothesis, but not anymore.

“Obesogens are definitely a contributing factor to the obesity epidemic,” Bruce Blumberg, an obesity and endocrine disruptor expert at the University of California, Irvine, told me over email. “The difficulty is determining what fraction of obesity is related to chemical exposure.”

It is important to note that recent research demonstrates that obesogens act to harm individuals in ways that traditional chemical toxicity tests cannot detect. In particular, the consequences of chemical exposure may not appear during the lifetime of an exposed organism, but may be transmitted by so-called epigenetic mechanisms to offspring, even several generations later. A typical example is tributyltin or TBT, a chemical used among other things in wood preservatives. In experiments exposing mice to low and supposedly safe levels of TBT, Blumberg and his colleagues found a significant increase in fat accumulation over the next three generations.

TBT and other obesogens trigger such effects by directly interfering with the normal biochemistry of the endocrine system, which regulates energy storage and utilization, as well as human eating behavior. This biochemistry depends on a wide variety of hormones produced in organs such as the gastrointestinal tract, pancreas and liver, as well as chemicals in the brain capable of altering the feeling of hunger. Experiments have shown that mice exposed to obesogenic chemicals before birth show significantly altered appetites later in life and a propensity for obesity.

Nearly 1,000 obesogens with such effects have already been identified in animal or human studies. They include bisphenol A, a chemical widely used in plastics, and phthalates, plasticizing agents used in paints, drugs and cosmetics. Others include parabens used as preservatives in food and paper products, and chemicals called organotins used as fungicides. Other obesogens include pesticides and herbicides, including glyphosate, which a recent study found to be present in the urine of most Americans.

Another clue that these chemicals could be the cause of obesity: studies have shown that the obesity crisis also affects cats, dogs and other animals living in close proximity to humans. A significant increase in the incidence of obesity has even been noted in rodents and laboratory primates – animals raised under strictly controlled conditions of caloric intake and exercise. According to the researchers, the only possible factors behind these animals’ weight gain are subtle chemical changes in the type of food they eat or in the materials used to build their enclosures.

It is therefore possible that we have unwittingly saturated our living environment with chemicals affecting some of the most fundamental biochemical feedbacks controlling human growth and development. The obesity epidemic will likely persist, or get worse, unless we find ways to eliminate these chemicals from the environment, or at least identify the most problematic substances and drastically reduce the human exposure to them.

At the very least, it will require a transformation of how we test chemicals for toxicity, especially the many compounds that are ubiquitous in our foods, plastics, paints, cosmetics and other products. Discoveries in epigenetics have profoundly changed basic biological science and medicine over the past 15 years, but have not yet had much impact on current chemical safety testing practices. Scientists are pushing for change, but it takes time.

Hopefully proper testing methods will be adopted in the next few years. If they are not, we may well struggle to make any appreciable dent in this pernicious epidemic.

More other writers at Bloomberg Opinion:

To fight hunger, we need to fix food subsidies: David Fickling:

The number of calories in the menus is a boost, not a panacea: Thérèse Raphaël

Go ahead, order this cheesesteak: Faye Flam

This column does not necessarily reflect the opinion of the Editorial Board or of Bloomberg LP and its owners.

Mark Buchanan, physicist and science writer, is the author of the book “Forecast: What Physics, Meteorology and the Natural Sciences Can Teach Us About Economics”.

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