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Avoiding obesity prevents cancer

Published on April 11, 2024

Being overweight promotes cancer and makes both the early detection of tumors and their treatment more difficult, as Ralph Fritsch, Head Physician at the Clinic for Medical Oncology and Haematology, explains. This makes prevention all the more important.

Alongside tobacco and alcohol consumption, obesity is one of the most important preventable risk factors for cancer. There is a proven link to obesity for at least 13 types of cancer. These include carcinomas of the intestines, kidneys, oesophagus, pancreas and gallbladder and, in women, of the breast after the menopause, the uterus and ovaries.

Visceral fat in particular, which envelops the internal organs, is considered a cancer driver. The more overweight someone is and the longer the excess weight persists, the higher the risk. However, cancer cannot be traced back to a single factor – and cancer often develops without a recognizable risk factor.

Why being overweight leads to cancer

Adipose tissue is an active endocrine organ that produces estrogens and inflammatory messengers. Oestrogens can drive the growth of some types of cancer. Chronic low-threshold inflammation is also considered to be cancer-promoting. In addition, obesity causes the body to release more insulin, which is suspected of promoting the growth of cancer cells. The interrelationships are complex and not yet fully understood. The immune system also appears to be impaired by severe obesity.

The early detection, diagnosis and treatment of cancer can also be more difficult if you are overweight. In addition, overweight patients show an altered drug metabolism. Effective prevention therefore aims to avoid obesity from the outset or to systematically reduce it.

Endometrial cancer, cancer of the uterus, is a particularly impressive example. For this highly hormone-dependent type of cancer, the risk increases in parallel with the BMI, up to a seven-fold risk in patients with grade 3 obesity (BMI > 40). However, it is particularly important to note that being overweight increases the risk of developing many of the most common types of cancer, such as bowel, breast and pancreatic cancer. Excess weight also plays a role in the early detection, diagnosis and treatment of cancer.

Important preventive examinations such as colonoscopy can be more difficult to perform. Studies also show that severely overweight patients are less likely to take part in preventive programs such as mammography screening. Early detection is key here. In turn, therapy can be complicated if the patient is very overweight. For example, complications occur more frequently during surgical procedures, and the optimal dosage of cancer drugs is more difficult.

This is also higher for at least some types of cancer. This has been proven for bowel and breast cancer, for example. It is therefore important to tackle obesity after successful treatment in order to reduce the risk of a relapse. It makes particular sense for those affected to seek medical help from specialists.

That is a false conclusion. On the one hand because of the risks mentioned above, on the other hand, severe weight loss due to cancer is an unfavorable prognostic sign regardless of the initial weight.

Obesity is often a question of lifestyle: too much red meat, too much processed food, too much alcohol. Added to this is a lack of exercise. A holistic approach is therefore needed: nutrition, muscle building, psychological support. Accordingly, we work closely together at the Comprehensive Cancer Center of the USZ. All expertise is combined in one place. That is a great advantage.

This is based on the very good intention of contributing to the success of cancer therapy by changing the diet. It is important to approach nutrition during cancer therapy together with our nutrition specialists. There are no patent solutions that are right for all cancer patients, only principles on which a nutrition plan should be based. However, deficiency symptoms must be avoided at all costs in cancer therapy. We also advise against more radical, scientifically insufficiently proven dietary measures. We are fully committed to science.

Avoiding obesity from the outset is the best prevention. To achieve this, we need to start with children and young people. But it is never too late in life. Cancer is just one of the many health risks associated with being overweight. The quality of life suffers in many different ways.

Responsible specialist

Ralph Fritsch, PD Dr. med.

Senior Attending Physician, Department of Medical Oncology and Hematology

Tel. +41 44 255 22 14
Specialties: Gastrointestinal tumors, Hepatobiliary tumors, Molecular oncology and precision oncology