Obesity and Cancer: Excess Body Weight Is Linked to at Least 13 Cancer Types
Obesity is a significant modifiable risk factor for several cancers. The scientific literature estimates that obesity may cause between 4% and 8% of all cancer cases. The International Agency for Research on Cancer (IARC), an agency of the World Health Organization (WHO), officially recognises 13 cancers for which there is clear causal evidence of a link with obesity.
Moreover, recent studies suggest that this list may continue to expand.
Cancers Linked to Obesity
Based on current scientific studies and data, obesity is a risk factor — including in younger populations — for the following tumours:
- Endometrial cancer (cancer of the uterine lining)
- Oesophageal cancer
- Colorectal cancer
- Breast cancer (postmenopausal)
- Kidney cancer
- Pancreatic cancer
- Liver cancer (hepatocellular carcinoma)
- Gallbladder cancer
- Gastric cancer (cardia)
- Ovarian cancer
- Thyroid cancer
- Multiple myeloma
- Meningioma
Why Does Obesity Increase Cancer Risk?
Obesity is widely misunderstood. Adipose tissue behaves like an additional organ, with its own homeostasis and immune and endocrine functions.
The main contributing factors include:
- Inflammation
- Insulin resistance
- High IGF-1 levels
- Increased oestrogen production
- Leptin and adiponectin levels
- Tumour escape from the immune system
Together, these mechanisms create an environment that accelerates tumour growth and spread and helps tumours evade the immune system.
Not All Types of Obesity Carry the Same Risk
Research also shows that metabolic health must be taken into account.
People with metabolically unhealthy obesity have an elevated risk of several cancers compared with people of similar weight who have no significant metabolic problems. In this group, the risks are especially pronounced for cancers of the:
- Endometrium
- Liver
- Kidney
Here, the number on the scale alone does not capture the full risk picture.
New Links Are Emerging
A large population-based study from Sweden (>4 million participants) indicated links between obesity and several cancers, including some that have not previously been recognised in the medical literature as obesity-related.
Newly suggested associations include:
- Head and neck cancers
- Malignant melanoma
- Small intestine tumours
- Cervical cancer
- Lymphatic system tumours
In prostate cancer studies, obesity was found to increase the risk of advanced disease, while the relationship with locoregional cancer is weak.
The impact of obesity is also evident during treatment.
One meta-analysis showed that obesity is associated with:
- 14% higher mortality
- 13% higher mortality following medical care
The combination of biological mechanisms, hormonal changes, and a more complex bodily response to treatment increases the challenges of treating obesity-related cancers.
Can the Risk Be Reduced?
Yes, significantly.
One study showed that losing 10% or more of body weight is significantly associated with a reduced risk of developing certain cancers. Other important factors include:
- Regular physical activity
- A balanced diet
- Control of diabetes and other metabolic conditions
Long-term health benefits accompany every step towards a healthier lifestyle.
The Takeaway
Obesity is now one of the most important preventable risk factors for cancer. Current scientific evidence supports obesity as a causal factor for 13 different cancer types, and further studies will likely extend that list.
This is why the way cancer prevention is taught and communicated needs to be reconsidered.
Disclaimer: This article is for informational purposes only and does not replace professional medical consultation. If you have questions about your individual cancer risk or are planning weight reduction, please consult your treating physician or another qualified healthcare professional.