Excessive weight loss may raise colorectal cancer risks

A significant reduction in body weight is often considered a positive change for health but researchers have warned that in some cases, the opposite may be true.

According to a recent study conducted in Germany, people who lose more than 10% of their body weight have a 50% higher risk of dying from colorectal cancer compared with others.

Among patients already diagnosed with the disease those who lose weight also have a 33% higher risk of cancer recurrence. However, scientists at the German Cancer Research Center clarified that these findings do not mean that gaining weight can prevent colorectal cancer.

Instead, they said that significant weight loss in the months or years before a cancer diagnosis may be a lesser-known sign that the disease is already affecting the body and should not be ignored.

Colorectal cancer is the third most common cancer worldwide. The number of new cases is expected to reach 3.2 million by 2040. In the United Kingdom alone, the disease causes approximately 17,700 deaths every year.

For reasons that are not yet fully understood, colorectal cancer cases are increasing rapidly among younger people. It is believed that more than half of cases could potentially be prevented through changes in diet and lifestyle. It is already known that obesity increases the risk of at least 13 types of cancer including colorectal cancer.

However, previous research has identified a phenomenon known as the “obesity paradox.” This refers to the observation that, in some cases, overweight or obese patients with colorectal cancer appear to survive longer than patients who have a healthy weight.

Experts believe one possible explanation is that people with higher body weight may be better able to tolerate the physical effects of cancer and its intensive treatments.

People with obesity also tend to have more frequent contact with their general practitioners because of various health problems. As a result, their cancer may potentially be diagnosed earlier.

However, experts have long argued that the so-called obesity paradox may be a misleading phenomenon. The healthy-weight group may contain an unusually large number of people who have already lost substantial weight because of cancer and who consequently have poorer treatment outcomes or disease progression.

Scientists say this situation can make overweight patients appear relatively healthier even though the reality may be the opposite. The study was published in the journal JAMA Network Open. Researchers analyzed data from 5,521 people with colorectal cancer who were followed for approximately five years.