The Hidden Danger: How Obesity Increases Cancer Risk

Obesity is a major cause of illness and death worldwide. Being overweight or obese elevates the risk of numerous health issues, including stroke, Obstructive Sleep Apnea (OSA), joint problems, and a weakened immune system. It also significantly heightens the likelihood of developing type 2 diabetes, cardiovascular diseases, and high blood pressure. Moreover, obesity is linked to an increased risk of 13 types of cancer. For instance, it raises the risk of uterine cancer by 7 times, esophageal cancer by 4.8 times, liver cancer by 2 times, and colon cancer by 1.3 times, among others, and also boosts the risk of cancer-related death.

According to 2020 data from the World Obesity Federation (WOF), around 1 billion people, or 1 in 7, are struggling with obesity. This aligns with the World Health Organization's World Health Statistics 2023 report, which states that 1.9 billion adults, or 39%, are overweight or obese. In Thailand, the Ministry of Public Health reported in 2023 that 48.35% of Thais are dealing with overweight and obesity issues, and these numbers are steadily rising.

Tanupol Virunhagarun, M.D., Chief Executive Officer of BDMS Wellness Clinic and BDMS Wellness Resort and President of Bangkok Association of Regenerative Health and The Study of Obesity (BARSO), along with Adjunct Professor, Teerawut Kuhaprema, M.D., Director of Bangkok Wattanosoth Cancer Hospital, are advocating to raise awareness about the dangers of obesity and to halt the growing obesity crisis as a means to reduce the number of cancer patients. While many factors increase the risk of cancer, such as smoking, alcohol consumption, and exposure to toxins or pollution, maintaining a healthy body weight is crucial in reducing cancer risk.

Understanding Overweight and Obesity

Dr.Tanupol explained that overweight and obesity are screened using the Body Mass Index (BMI). For Asians, a BMI of 23 kg/m² or more indicates overweight, and a BMI of 25 kg/m² or more indicates obesity. However, BMI is not always accurate in assessing obesity as it does not account for body composition. For instance, individuals with the same BMI might have different proportions of muscle and fat. Thus, BMI should not be the sole diagnostic tool.

Dr.Tanupol recommends using other measurements, such as waist circumference, which indicates accumulated visceral fat. For Asian adults, a healthy waist circumference should not exceed 90 cm (36 inches) for men and 80 cm (32 inches) for women. The most accurate method to assess body fat is through DEXA (Dual-Energy X-ray Absorptiometry) scan, which measures total body fat percentage. The American Council On Exercise (ACE) advises that middle-aged Asian women should have no more than 32% body fat and men no more than 25%.

To What Extent Does Obesity Cause Cancer?

Dr. Teerawut states that globally, obesity causes 3.9% of cancer cases, accounting for 544,300 cases. More cancer cases are found in women (368,500) than in men (175,800). In high-income countries, obesity accounts for approximately 8% of cancers, compared to only 1% in low-income countries.

Obesity also affects the treatment of existing cancer patients. Obese cancer patients are 17% more likely to die from cancer than non-obese patients and face more complications from treatment. The likelihood of cancer recurrence is 13% higher, particularly in breast and colon cancer patients.

How Does Obesity Cause Cancer?

Dr. Teerawut explains the mechanisms linking obesity to cancer risk:

• Hormonal Changes: Adipose tissue releases chemicals and enzymes into male and female hormones (estradiol and androgen). Excess estrogen production is linked to breast, endometrial, ovarian, and other cancers.
• Insulin and IGF-1 Levels: Obesity causes high insulin levels (Hyperinsulinemia) and elevated insulin-like growth factor 1 (IGF-1). Obese individuals often have insulin resistance, increasing the risk of diabetes and cancer. High levels of IGF-1 in the blood are associated with increased risks of colon, kidney, and endometrial cancers.
• Adipokines: Adipose tissue releases various adipokines, such as leptin, which promotes inflammation and accelerates cell growth, inhibiting natural cell death (apoptosis). Conversely, obesity reduces adiponectin, which inhibits cell expansion, leading to abnormal cell growth and cancer.
• Chronic Inflammation: Adipose tissue causes chronic inflammation, with substances like IL-6, TNF-Alpha, and CRP increasing cancer risk. Chronic inflammation weakens the immune system and alters the tissue environment, facilitating cancer development.

Dr. Tanupol adds that abnormal fat hormone secretion affects immune function by reducing the efficiency of NK-cells (Natural Killer Cells), which plays a crucial role in destroying cancer cells. The risk of cancer increases with body weight and the duration of obesity.

Unhealthy Eating Habits Increase Cancer Risk

Consuming more energy than needed over time leads to obesity and other chronic non-communicable diseases (NCDs). Specific foods are clearly linked to type 2 diabetes, cardiovascular disease, and cancer. The International Agency for Research on Cancer (IARC) classifies processed meat (e.g., sausages, salami, ham, bacon) as carcinogenic to humans (Group 1), with sufficient evidence linking it to colon and stomach cancers. Red meat (e.g., beef, lamb, pork) is classified as possibly carcinogenic (Group 2A).

The preservatives 'nitrate' or 'nitrite' used in meat processing can become carcinogenic (Nitrosamines) within the body. Cooking methods like baking and grilling also produce carcinogens such as heterocyclic aromatic amines (HAA) and polycyclic aromatic hydrocarbons (PAHs), which can damage intestinal wall cells.

Consuming 50 grams of processed meat daily increases the risk of colon cancer by 18% and type 2 diabetes by 51%. High consumption of red and processed meat is a risk factor for obesity due to their high energy content, cholesterol, and saturated fats.

Healthy Diet and Exercise

Dr.Tanupol recommends maintaining a healthy diet and regular exercise to manage body weight and reduce cancer risk. He suggests reducing red and processed meat intake, and opting for plant-based proteins such as soybeans, tofu, and chickpeas. Additionally he advises consuming a variety of vegetables, whole grains, and mushrooms.

A plant-based diet, emphasizing unprocessed plant foods, can reduce cancer incidence and other NCDs such as obesity, heart disease, and diabetes. Increased dietary fiber from plant-based foods helps maintain body weight and prolongs satiety.

Exercise and Cancer Prevention

Regular exercise, at least 30 minutes a day, 5 days a week, helps reduce cancer risk by controlling cancer-related hormones, promoting immune function, accelerating food movement through the intestines, and preventing obesity.

Research published in PLoS One in 2018 showed that at least 150 minutes of aerobic exercise per week reduces cancer cells in the bloodstream of stage 1-3 colon cancer patients. Consistent physical activity can also decrease the risk of cancer recurrence and death.

Maintaining a healthy lifestyle, which includes proper diet, regular exercise, good sleep quality, and a pollution-free environment, is crucial for cancer prevention. "Good health is the most important treasure."