We know that there are many contributors to weight gain and obesity in the modern world.  We talk a lot about contributors like the powerful genetics that underpin obesity for many people, alterations in hormones produced by our gut/pancreas/fat tissue, and the reward response in our brains.  We also talk about our environment, in that most modern societies are rife with unhealthy food choices, oversized portions, and ‘advancements’ that allow us to move less and less in our daily lives.  But could environmental chemicals actually be a focal point of this storm?

That’s exactly what a recent review article, published in the International Journal of Obesity, suggests.

In this article, authors discuss four models as to the cause of obesity:

  • Energy Balance Model: essentially, that weight gain occurs when calories in (food/drink) are greater than calories out (energy burn)
  • Carbohydrate-Insulin Model: increased carbohydrate intake in highly palatable foods leads to increased insulin secretion, insulin resistance, and fat storage
  • Oxidation-Reduction (REDOX) Model: reactive oxygen species are signaling molecules generated by our body which alter metabolic signaling, contribute to low grade inflammation, and promote fat storage
  • Obesogen Model: environmental chemicals (called obesogens) interfere with hormone signaling, leading to obesity.

The authors propose that the problem starts with the harmful environmental chemicals, which generate false hormonal signals in our body, including an increase in the production of reactive oxygen species.  Obesogens also alter our gut bacteria and even the expression of our DNA (called epigenetic changes). These changes cause dysfunction in our appetite regulating hormones, promote insulin resistance, increase insulin secretion, and disrupt our body’s energy nutrient handling and efficiency,  with the ultimate results being altered brain control of food intake and a slower metabolic rate, which together drive weight gain and obesity.

So where are these obesogenic environmental chemicals? It turns out that they are… everywhere. For example:

  • Ultraprocessed foods – often containing obesogenic additives, preservatives, emulsifiers
  • Pesticides
  • Chemicals in scented products
  • Non stick cookware coatings
  • Chemicals in drinking water
  • Antibiotics, necessarily taken for a bacterial infection, but can have consequences on gut bacteria
  • Chemicals in the air we breathe

If the environment is indeed at the center of the obesity pandemic, why doesn’t everyone have obesity?  Well, remember that genetics have a powerful influence in body weight, as well as where our body wants to store fat (in the healthier depots under the skin vs the more metabolically dangerous visceral fat around the abdomen and in/around internal organs). So, genetically prone individuals may be more susceptible to the influence of environmental chemicals.  Remember also that there are many potential causes and contributors to weight gain and obesity, and each individual’s journey is unique.

However much environmental obesogenic chemicals are contributing to the obesity pandemic, there is no doubt that more aggressive strategies are urgently needed to understand their influence, and to work to limit them through societal intervention and obesity prevention strategies.

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