For a long time, France believed itself spared by the obesity epidemic. Immunized, thanks to its gastronomy, its meals at a fixed time, or a certain taste for walking. This is far from the case: between 1990 and 2020, the number of people with obesity doubled, from 8.5 to 17 %, according to a study by the National Institute of Health and Research medical (Inserm). France does not want to see it, but it has, no doubt, an important weight problem.
From this crisis which worsens from year to year, there could be another. Because of overweight, cancer cases are also going to fly away. Because obesity is an important risk factor for tumor: people with a strong weight -bearing develop much more often this pathology than the rest of the population. According to the International Center for Research on Cancer (Circ/OMS), 16 types of different cancers are more particularly concerned (prostate, breast, pancreas, etc.).
The subject is the subject of increasingly lively attention from scientists: with approximately one in eight people with obesity in the world ofAfter the WHO,, Overweight is now considered the third cause of so -called “avoidable” cancers behind alcohol and smoking. About 19,000 cancers screened each year are linked to an excess of fat, according to theNational Cancer Institute.
For a long time, related factors have been cited – overweight people are often more sedentary, more enclosed to drink and smoke, for example. But for a few years, the fat itself has also been designated: “More and more studies have been showing its involvement in the appearance and aggressiveness of malignant tumors. Fat is not only part of, it is a Direct culprits “, summarizes Catherine Muller, deputy director of the Institute of Pharmacology and Structural Biology at the University of Toulouse, and author of a literature review published in 2020 in the scientific journal Trends in Cancer.
Fat nourishes tumors
A week ago, the Cancer League invited the researcher to present her work, on the occasion of her annual conference. The choice of the association, which pays more than 40 million euros each year to research, is not surprising: the scientist is one of the most advanced on the subject. With her team, she highlighted several of the incriminated mechanisms, for several cancers, including those of prostate, breast, or bone cancer, in the past twenty years.
When consumes fat, cells called “adipocytes” are responsible for storing part. In case of significant physical activity or deprivation of food, “release” of fat, “lipids”, can take place, to help other cells. What Catherine Muller shows is that tumors are capable of “mimicking” these situations, hacking this natural functioning. They can thus “force” the surrounding adipocytes to release lipids and fatty acids, and “feed them” to prosper. Results initially presented in 2011 in the scientific journal Research cancer For breast cancer, and replicated, then, with many other locations of the disease.
“Cancer cells are capable of producing lipids themselves, but they can also be used in the body’s reserves. These mechanisms diverge according to the nature of lipids, the type of tumor, its aggressiveness, its migration capacity, But we think there is a key mechanism to understand in patients with obesity. summarizes the researcher.
In the presence of adipocytes, tumors can be more aggressive. They develop faster, are larger, and make more metastases, these secondary sizes that develop elsewhere in the body. “Conversely, adipocytes decrease in size and secrete more pro-inflammatory molecules in the presence of cancer cells,” continues the researcher. In theory, everyone could be affected by the phenomenon, but people with obesity are more likely to present fatty pockets near tumors.
Toxic molecules
Other mechanisms intervene: “The fatty fabric in people in obesity is not only more frequent, it is also more often dysfunctional, it will more often release certain toxic molecules, or at least whose presence is abnormal “Adds Catherine Muller. A mechanism that Vinciane Rebours, coordinator of the National Reference Center for Rare Diseases of the Pancreas at the Beaujon de Clichy hospital. The specialist closely studies pancreatic cancer, one of the most associated with overweight.
The researcher notably highlighted the higher frequency of “precancerous lesions” in the presence of an excess of fat. A study published in 2015 in the journal Clinical Cancer Research. “Fat too much can accumulate and end up infiltrating pancreatic cells. This is shown in the case of pancreatic cancer. It can also promote, stimulate certain activation routes, reactions in reactions A chain that will cause an abnormal cellular functioning.
These mechanisms, also detailed in a study published in March 2024 in the journal Scientific Reportsare not obesity either. But they are accentuated by pathology: “It also happens that people have an abnormal functioning of their organ, which will generate inflation and, ultimately, promote the appearance of toxic adipocytes. In the case of Pancreas For example, some genetic anomalies create pancreatitis, which makes the pancreas become too fatty, “continues Vinciane Rebours. Ultimately, scientists hope that this work will develop new drugs. This is far from the case for the moment.
As this research is popular, some uncardvantly conscientious doctors have (already) mentioned the idea of depriving themselves of fat, to slow down the spread of tumors. A false good idea: “To be effective, it would be necessary to target the fat that intervenes in cancer cells. If you deprive yourself of fat, it is the whole organism that we weaken, including the immune system supposed to fight against The tumors.
Upon arrival on the market, anti -Besity drugs have caused significant hopes in this area. People who benefit from it often have less cancers. But scientists do not know if these effects are caused by the drug, weight loss, or improving other factors, such as being able to regain normal physical activity. Clinical studies must be launched, to hope to demonstrate an effect. In the meantime, Vinciane Rebours is skeptical: “It will be necessary to demonstrate that the mechanisms stimulated by these drugs do not lead to precancerous lesions in the mobilized organs”, nuances the scientist.
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