What is fattening around?

By Maya Falah, Angle, Science and Environment News Agency

Obesity has long been defined as an epidemic in the western world and it is starting to spread in developing countries as well. Of course, this is not just an aesthetic matter: obesity causes a variety of health problems such as heart disease, diabetes, narrowing and clogging of blood vessels and high blood pressure, and can even lead to death. So how does all this relate to the air we breathe? Researchers have long been able to show that there is a connection between exposure to high levels of air pollution andTendency to develop excess weight. But now, researchers hypothesize that actually air pollution causes obesity indirectly: by changing our behavior.

In a comprehensive study that has been taking place in Mexico for the past decade, the researchers are monitoring the effect of various factors on obesity. As part of the study, called PROGRESS (Research program to examine obesity, growth, environmental and social stress factors), the researchers perform a series of tests on children over a long period of time, starting from the mother's pregnancy stage, in an attempt to assess the risk factors that may cause the phenomenon of obesity.

"In the last twenty years there has been a sharp increase in the percentage of children suffering from obesity around the world," says Prof. Robert Wright of the Mount Sinai Hospital School of Medicine in New York, who recently lectured at a special conference of The Health and Environment Fund, "This is alongside a significant increase in the same period in the percentage of children in the population who suffer from ADHD (ADHD). These two issues have been linked to environmental factors in the past, but no study has tested to date - to the best of our knowledge - whether they affect each other, or whether even one of them may cause the other.'

Indeed, the claim does not sound unreasonable when you look at the list of factors that may lead to the development of each of the phenomena: studies have proven that environmental effects such as exposure to certain chemicals (such as phthalates and BPA - substances found in plastic), exposure to air pollution and inhalation or ingestion of various metals may affect on the metabolic system and cause obesity. Interestingly, other studies link almost exactly the same factors even when affecting the nervous system and brain. This, as mentioned, lit a light of suspicion in Wright and his team of researchers and they decided to examine whether there might be a connection between these two phenomena.

"What we wanted to test was divided into several questions," says Wright, "Are these phenomena influenced by environmental factors? Are they related to each other? And if so - in what order do they happen? That is, does the development of certain neurological disorders cause obesity, or is it the other way around?'

The study in Mexico provided researchers with an excellent ground to try and test these questions. The study takes place in Mexico City in a large area of ​​the city, and follows the same children over the years, even when they were in their mother's womb. "It is now known that the fetal environment affects human health as an adult," Wright explains. "Studies from several decades ago already showed that babies whose mothers suffered from hunger during pregnancy tended to be fatter adults. It is commonly thought that this is caused by things that happen to the fetus in the context of metabolism - such as changes in metabolism and the development of insulin resistance, which impairs the ability to lower the blood sugar level. But what if there are also effects of various factors on the fetal brain, which indirectly cause obesity? Could it be that both phenomena are actually part of the same evolutionary strategy, which is built and developed already in the embryonic environment?"

"Today it is also clear that behavior patterns are related to the issue of obesity," he adds. "Certain cognitive abilities and behavioral patterns such as impulse control and the ability to stay focused on a task are known predictors of obesity. Impulse control, i.e. impulsivity, is the main predictive factor from a behavioral point of view."

As part of the study, the researchers examined the children (and their mothers) during the second and third trimesters of pregnancy, and then once more at the age of 7-4, using physical tests and questionnaires. In addition, to estimate the levels of exposure to air pollution, the researchers used a model developed by Prof. Itai Kellogg from Ben Gurion University, which is based on measuring daily air pollution data from NASA and maps the point exposure to pollution in the study area in Mexico, with the aim of estimating how much air pollution is exposed to each day Each of the children participating in the study according to their area of ​​residence.

The researchers also tested the concentration of metals in the children's bodies based on a new technique: it turns out that the child's milk teeth can tell about the level of his exposure to different metals during his life stages. With this technique, the experts check the baby teeth that have fallen out, and similar to the rings that can be seen in a cut tree trunk that teach about its age, the layers of the tooth also tell the story of the child's life: from the various materials that make up the layers of the growing tooth - which develop in the fetus during the stages of pregnancy until the baby reaches the age of 11 Months - it is possible to learn how much the child was exposed to metals and at what stage.

This is still an ongoing study, but according to Wright, the results of the research so far indicate that there is indeed a connection between air pollution and obesity, and that this connection is not necessarily direct - but goes through an intermediary: it appears that exposure to high levels of air pollution causes oxygen deprivation in the initial life stage of the fetus, which leads to disorders in brain development that cause neurobehavioral disorders (such as a pattern of difficulty controlling impulses), which in turn causes obesity.

"Personally, I believe obesity has a lot to do with neurobehavior, more than the body's metabolic rate," says Wright. "Eating that is influenced by behavioral patterns is, in my opinion, one of the main causes of obesity, and research also supports the connection between them. What we have added here is that what causes the development of these behavior patterns are, among other things, the levels of air pollution, the toxic chemicals and metals that the fetus or child is exposed to - that is, it is the pollutants that cause changes in behavior, which affect the tendency to develop obesity. The conclusion here is that the environment may indeed cause obesity, but it does so through an influence on behavior, and not directly.'

Open a window

Another thing that the researchers try to do in the study is to identify what the 'windows of sensitivity' are (Windows of susceptibility) - that is, to assess the time windows in which the fetus (and then the child) is particularly sensitive to exposure to certain factors, such as air pollution and metals. Since the model referred to the levels of air pollution measured every day starting in the second trimester of pregnancy and from the analysis of the development of the teeth it was possible to understand the data of the child's exposure to metals throughout development, the researchers could follow the data and try to map the critical time windows in which these factors may have a particular effect - for example, at what stage Is there a window of sensitivity that may have the greatest impact on the development of an impulsive behavior pattern in the baby?

"It has been known for many years that there are stages at the beginning of life when the brain has greater plasticity. Thus, for example, a child is able to learn a language by the age of five or six much more easily than later in life. In other words, there is a kind of window of opportunity for learning a language," Wright explains. "Similarly, it is known that there are stages in life when exposure to chemicals can affect the brain more than at other stages, later in life. Today, for example, it is common to assume that the window of sensitivity for exposure to lead is at the age of two - that around this age the exposure can cause the most damage. This is known because it is the most tested chemical, but there is not much such data today on other substances. In other words, we believe that the issue of sensitivity windows to different exposures exists, but it is something that has not yet been systematically tested.'

"Today, the development of new technological tools can make it possible to test and compare the effects of exposure at different ages," says Wright. "Thus, for example, our use of dental tests to assess the exposure of the fetus and the child to metals allows us to assess with increasing precision when the windows of sensitivity occur among the children and thus know when it is most important to reduce the exposure to various risk factors. In the research, we found that there is a window of time in which the fetus is prone to the development of impulsive behavior patterns - which occurs in the third trimester of pregnancy, so at this stage, for example, it is advisable to make a special effort to avoid exposing the mother to high levels of air pollution.'

"If we correctly understand these patterns and the windows of sensitivity, it can help us both reduce the tendency to obesity in the population, and also better understand how it should be treated," concludes Wright. "First of all, we will know that it is important to reduce the exposure to problematic factors at important points in time, when we need to be more careful. We will also be able to identify children who are at a higher risk of obesity due to exposure during pregnancy, and give them the appropriate cognitive therapy that will help prevent them from suffering from obesity."