Overweight people with colorectal cancer have a 55% reduced risk of death compared to people of normal weight.
Overweight people with colorectal cancer are less likely to die from it than those with normal weight, according to an American study published this Thursday in the review JAMA Oncology.
In France, colorectal cancer is the third most common cancer, all sexes combined. Last year 43,000 people were affected and 17,500 died. By 2020, experts estimate that the number of colon-rectal cancer could reach 45,000 new cases annually.
Age is the main risk factor: it occurs mostly in people over 50. Being overweight is also associated with an increased risk of colorectal cancer. However, many studies have shown that the prognosis is more favorable for overweight people than for those with a normal BMI between 18.5 and 23.
A risk reduced by 55%
To better understand this phenomenon, a team from the Kaiser Permanente Division of Research (United States) examined the medical records of 3,400 men and women suffering from this cancer between 2006 and 2011. The researchers assessed their risk of death based on their weight at the time of diagnosis and then 15 months later.
After adjusting their results according to their socio-economic level, the severity of their disease, or other risk factors, the researchers observed that patients of normal weight, those who were underweight (BMI less than 18.5) and obese people (BMI over 35) have an increased risk of mortality.
On the contrary, overweight patients (BMI between 28 and 30) have a 55% reduced risk of dying from colorectal cancer compared to patients of normal weight. “Our work, which represents the largest cohort of colorectal cancer patients to date, supports the notion of the obesity paradox,” said Dr. Candyce Kroenke, head of the study.
Ideal weight varies
However, the researchers indicate that the biological mechanisms that can explain this phenomenon are not known. Additional work will therefore have to be carried out to identify them.
Scientists believe, however, that these results suggest that the ideal weight associated with the best prognosis for cancer differs from that for preventing its onset. “And just as the treatments change according to the cancers, the ideal weight could also vary according to the location of the tumors”, supposes Bette Caan, one of the authors of the study.
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