01 Jul Is colorectal cancer related to obesity?

in www.msn.com – 26 June, 2025

Colorectal cancer (CRC) is one of the most prevalent and deadly cancers both in Europe and worldwide. In Portugal, it ranks as the most diagnosed cancer, the second leading cause of cancer-related deaths, and the sixth leading cause of death overall.

Colorectal cancer (CRC) is influenced by a range of risk factors, some of which are non-modifiable—such as gender, a family history of cancer or colorectal polyps, and the presence of inflammatory bowel disease. However, a significant proportion—estimated at 70 to 90 percent—of CRC cases are linked to modifiable risk factors. These are primarily associated with diet and lifestyle, including excess body weight, physical inactivity, smoking and alcohol consumption, and a diet high in processed or red meat and low in fruits and vegetables. This dietary pattern also associated with obesity.

According to the World Health Organisation, there are currently 650 million adults worldwide who are overweight, defined as having a body mass index (BMI) greater than 25 kg/m². In Portugal, 67.6% of the population is overweight and 28.7% of adults aged between 25 and 74 are obese (BMI ≥ 30 kg/m²).

Obesity is a well-established risk factor for colorectal cancer (CRC). Compared to individuals with a normal body mass index (BMI), obese individuals face a 7% to 60% higher risk of developing CRC. This association is stronger for colon cancer than for rectal cancer, and the relationship is both direct and independent: for every 2 kg/m² increase in BMI, the risk of CRC increases by approximately 7%. The risk is more pronounced in men. For every 5 kg/m² increase in BMI, the risk of CRC rises by 24% in men and 9% in women. It’s important to emphasise, this elevated risk begins early in life — it has been observed in obese children as young as 7 years old, as well as in young adults, highlighting the importance of early prevention and intervention.

The risk of CRC is particularly associated with visceral fat, assessed above all by intra-abdominal fat: every 2 cm increase in waist circumference translates into a 4 per cent increase in the risk of CRC.

The pathophysiological link between obesity and cancer is complex and multifactorial. It involves a combination of metabolic dysregulation (such as insulin resistance), chronic low-grade systemic inflammation, and hormonal imbalances. Emerging evidence also suggests that the gut microbiota plays a significant role in this association.

The treatment of colorectal cancer (CRC) in obese individuals presents additional technical challenges, particularly in surgical approaches. In addition to increasing the incidence of the disease, obesity is also associated with higher rates of recurrence and mortality. Individuals with a higher BMI and greater amounts of visceral fat tend to have lower overall survival. Furthermore, CRC-related mortality increases progressively with the number of metabolic syndrome factors present – such as diabetes mellitus, hypertension, and dyslipidemia – which are frequently associated with obesity.

Also important is sarcopenic obesity, characterized by a reduction in skeletal muscle mass in individuals with obesity, a particularly serious condition in the oncological context, associated with a worse clinical prognosis and requiring early diagnosis.

Fortunately, recent studies have shown that bariatric surgery with sustained weight loss reduces the risk of CRC, demonstrating that this risk relationship can be modified.

It is therefore imperative to act early, promoting healthy lifestyles and eating habits from childhood as a fundamental strategy for reducing the incidence and mortality not only from CRC, but also from all obesity-related diseases.