The Guardian reports on three review papers showing that chemical pollutants called “obesogens” are contributing significantly to the world’s obesity epidemic.
Citing 1,400 studies, they say these chemicals are in water and dust, food packaging, personal hygiene products and household cleaners, furniture and electronics.
Prof Robert Lustig at the University of California, San Francisco, said, “If I had to guess, based on all the work and reading I’ve done, I would say obesogens will account for about 15% to 20% of the obesity epidemic. But that’s a lot.” The rest he attributes to processed food diets, which themselves contain some obesogens.
“Fructose is a primary driver of a lot of this,” he said. “It partitions energy to fat in the liver and is a prime obesogen. Fructose would cause obesity even if it didn’t have calories.”
An ultra-processed diet can cause more weight gain than an unprocessed diet, despite containing the same calories.
Obesogens work by upsetting the body’s “metabolic thermostat”, the researchers said, making gaining weight easier and losing weight harder. The body’s balance of energy intake and expenditure through activity relies on the interplay of various hormones from fat tissue, the gut, pancreas, liver, and brain.
The pollutants can directly affect the number and size of fat cells, alter the signals that make people feel full, change thyroid function and the dopamine reward system, the scientists said. They can also affect the microbiome in the gut and cause weight gain by making the uptake of calories from the intestines more efficient.
“It turns out chemicals dumped in the environment have these side effects, because they make the cells do things that they wouldn’t otherwise have done, and one of those things is laying down fat,” said Prof Robert Lustig.
Global obesity has tripled since 1975, with more people now obese or overweight than underweight, and is increasing in every country studied. Almost 2 billion adults are now too heavy and 40 million children under five are obese or overweight.