Studies have found that many cancers are related to obesity. Nowadays, more and more people are becoming obese. However, doing two things can easily achieve the effect of cancer prevention and weight loss.
According to the Centers for Disease Control and Prevention (CDC), obesity will increase the risk of 13 types of cancer, and these cancers account for 40 percent of all cancers diagnosed in the United States each year, including breast cancer, colon cancer, stomach cancer, liver cancer, esophageal cancer (esophageal adenocarcinoma), pancreatic cancer, kidney cancer, ovarian cancer, uterine cancer, gallbladder cancer, thyroid cancer, meningioma (a type of brain cancer), and multiple myeloma (a type of blood cancer).
Compared to those with normal weight, the risk for several cancers increases substantially for those who are obese or overweight:
- Endometrial cancer: The risk is seven times higher for those with severe obesity, and two to four times higher for those who are obese or overweight.
- Esophageal cancer (esophageal adenocarcinoma): The risk is 4.8 times higher for severely obese people and 1.5 to three times higher for obese or overweight people.
- Stomach cancer (gastric cancer): The risk is twice as high for obese people.
- Liver cancer: The risk is twice as high for obese or overweight people.
- Kidney cancer: The risk is twice as high for obese or overweight people.
- Pancreatic cancer: the risk is 1.5 times greater for obese or overweight people.
- Colorectal cancer: The risk is 1.3 times greater for obese or overweight people.
- Gallbladder cancer: The risk is 1.6 times greater for obese people and 1.2 times greater for overweight people.
- Meningioma: The risk is 1.5 times greater for obese people and 1.2 times greater for overweight people.
- Breast cancer (after menopause): The risk is 1.2 to 1.4 times greater for obese or overweight people.
- Thyroid cancer: The risk is 1.2 to 1.3 times greater for obese or overweight people.
- Multiple myeloma: The risk is 1.1 to 1.2 times greater for obese or overweight people.
- Ovarian cancer: The risk increases 1.1 times for every five-point increase in body mass index (BMI).
From 2005 to 2014, among Americans with new cancers, the cancers unrelated to obesity decreased by 13 percent. However, the incidence of obesity-related cancers increased by 7 percent, with the exception of colorectal cancer, which can be detected and prevented in advance with screening.
The most common type of cancer in obese men is colorectal cancer. In women, it’s breast cancer after menopause.
Among the above 13 types of cancer, more than 90 percent of new cancer cases occur in people aged 50 years or older. The longer a person stays obese or overweight, the greater the risk of cancer.
Obesity and Cancer: Shared Causes
Dr. Chih Ying Liao, director of Radiation Therapy and Integrative Oncology Department at MOHW Taichung Hospital in Taiwan, pointed out that obesity is only one of the “manifestations” of these problems. Obesity is related to poor dietary habits, lifestyle, and metabolic factors, which themselves have the risk of promoting cancer.
For instance, frequently consuming fried foods, desserts, barbecued meats, and other unhealthy foods and not doing enough exercise are contributors to obesity, as well as cancer. After being fried, pan-fried, or grilled, meat will produce carcinogenic substances, such as heterocyclic amines and polycyclic aromatic hydrocarbons.
In particular, after being roasted or prepared through other high-temperature cooking methods, red meat tends to produce advanced glycation end products (AGEs), resulting in chronic inflammation and increasing the chance of cancer. If too many desserts are consumed, the sugar in them can bind to the protein molecules in the body and, after a series of reactions, can also form glycation end products.
Long-term chronic inflammation and metabolic syndrome related to obesity, as well as higher than normal levels of insulin and insulin-like growth factors, will cause cancer cells to grow.
There are usually cancer cells circulating in the body. When the body is in good shape, the immune cells can kill the cancer cells. However, when the metabolic system and the immune system become weakened, it will be very difficult to kill cancer cells. Obesity allows cancer cells to multiply more easily and continuously.
In addition, a study conducted in Taiwan in 2017 confirmed the relationship between obesity, adipocytes (fat cells), and cancer. Researchers found that an MCT2 protein on the membrane of breast cancer cells acts as a gateway, sending metabolites that are spit out by adipocytes to breast cancer cells as nutrients, thus helping breast cancer cells grow.
Losing Weight can Reduce the Risk of Cancer
The definition of obesity is different for everyone because of factors such as height, muscle mass, body shape, and so on. Body mass index (BMI) can be used as one basis for determining whether someone is obese, but it has limitations as well, since it doesn’t account for muscle mass or waist circumference.
For most people, however, BMI is a good indicator of healthy bodyweight, since it’s based on weight and height.
According to Liao, if someone has a BMI higher than 25, he or she is overweight; higher than 27 is mild obesity; and higher than 30 is moderate obesity. The higher the BMI, the stronger the cancer-causing factor of obesity, so attention should be paid to those with a BMI of higher than 27.
The CDC divides obesity into classes. People with a BMI from 30 to 35 are class 1, 35 to 40 are class 2, and 40 or higher are class 3, sometimes categorized as “severe” obesity.
Another simple way to determine obesity is to measure the waist circumference. This can also correlate with cancer risk. Women with a waist circumference of 32 inches or more and men with a waist circumference of 35 inches or more have a higher risk of developing cancer. Liao said the longer the waist circumference, the more serious the abdominal obesity and the higher the visceral fat content, meaning that the body is in a state of chronic inflammation with abnormal metabolic problems.
Therefore, obese people need to lose weight to reduce the risk of cancer. However, how much weight should they lose to be safe?
“Obese people who lose 5 percent of their current body weight will have reduced the risk of cancer,” Liao said.
In other words, a 150-pound person who loses 7.5 pounds will have a statistically relevant drop in their risk of cancer. He pointed out that although the ideal state is to reduce the weight to a BMI value of 25 or less, for many obese people, that would be difficult, and they might give up halfway.
Another method is to keep the waist circumference less than 31.5 inches in women and 35.5 inches in men, in order to reduce visceral fat.
Anti-Cancer Weight Loss Methods
There are various ways to lose weight. However, using the wrong way or unsuitable ways to lose weight will make the body even more unhealthy.
According to Liao, exercise, a balanced diet, and consuming a lot of fruits and vegetables are ways that everyone can use to lose weight. In terms of diet, he recommended the Mediterranean diet, as well as eating fewer carbohydrates. People tend to eat too many carbohydrates, especially the over-processed carbs found in processed foods.
The Mediterranean diet is composed of vegetable-based meals, with high-quality proteins, whole grains, and healthy oils.
The word “fats” may make dieters feel uneasy, but the Mediterranean diet doesn’t avoid fats while having the same weight-loss effect. A study published in the American Journal of Medicine found that the Mediterranean diet is more effective than a low-fat diet. People who adopt the Mediterranean diet can lose up to 22 pounds of body weight in one year.
Another study of more than 32,000 participants, which was conducted in Italy, shows that long-term adherence to the Mediterranean diet was associated with a reduced risk of abdominal obesity over a five-year period.
The Mediterranean Diet
The Mediterranean Diet is already linked to healthy longevity, meaning researchers have found that people who follow this diet live longer and with fewer illnesses. The following are the key components of the Mediterranean diet.
Vegetables and Fruits
This diet is based on eating lots of vegetables with an appropriate quantity of fruits.
Vegetables and fruits are rich in dietary fiber, which can absorb toxins in the intestines and slow down the rise of blood sugar and the rate of blood glucose absorption. When the absorption of blood sugar becomes slower, the secretion of insulin and insulin-like growth factors will be reduced.
Fiber-rich foods can also balance and reduce the intake and absorption of fats and cholesterol, so that the body is less likely to accumulate visceral fat or produce excessive cholesterol. The more dietary fiber you consume, the easier it is to feel satiated. Fiber also promotes intestinal motility and helps with bowel movements.
A 2018 review study in Nutrients shows that eating more vegetables was associated with lower body weight and reduced waist circumference.
Eating multicolored fruits and vegetables also provides access to a wide range of nutrients, including phytochemicals, which help the body resist oxidation and improve chronic inflammation.
We should consume more vegetables than fruits because of the higher sugar content in fruit, which can interfere with blood sugar control and cause weight gain.
This diet includes eating plenty of legumes, seafood, eggs, white meat, and dairy products, such as Greek yogurt.
Eating soybeans, black beans, chickpeas, and other legumes, as well as bean products, can help you lose weight. An analysis published in the American Journal of Clinical Nutrition compiled data from 21 clinical trials and concluded that adding legumes to the diet may be a beneficial weight loss strategy—even if there’s no intention to restrict calories—and can result in a moderate weight loss.
Adopting the Mediterranean diet can also reduce the intake of red meat. However, when cooking seafood and white meat, we should also avoid pan-frying, grilling, frying, and other high-temperature cooking methods.
Brown rice, black rice, quinoa, and oats are examples of healthy whole grains people eat on this diet.
According to Liao, people who want to lose weight should reduce their intake of foods high in refined starches, such as pastries, white bread, and over-processed pasta. Replace these kinds of staple food with whole grains.
Fish and Plant-Based Fats
Fish, olive oil, avocados, nuts, and seeds are the main sources of fats on the Mediterranean diet.
Fatty fish, such as salmon, are high in omega 3 fatty acids, which are linked to several health benefits. And all of these plant-based fats have been shown to have cancer-preventive effects. When cooking with good oils, such as olive oil, you can also add some herbs or spices to enhance flavor and reduce the amount of salt used.
Train Muscles to Secrete Cancer-Fighting Hormones
In addition to adjusting our diet, exercise is also important. Liao said both aerobic exercise and muscle training should be taken into account.
In particular, weight training to strengthen muscles can reduce insulin resistance, increase basal metabolic rate, and improve fat metabolism. This is because muscles can secrete more than 3,000 types of muscle hormones. Muscle hormones can promote lipolysis, which is the process by which fats are broken down so that their stored energy can be used by the body. In particular, exercise can promote lipolysis of visceral fat, and several muscle hormones have potential anti-cancer effects.
In 2021, a study found that muscle hormones can inhibit tumor growth and even help actively fight cancer cells. Long-term exercise can produce a cancer-inhibiting environment in the body.
Finally, during aerobic exercise, the heart rate should reach at least 130 beats per minute, which means that the person will be panting. You’ll know you’ve reached the appropriate level of exertion if you can still talk, but singing is impossible.
This is the only way to effectively burn calories and improve metabolic problems.