It took until 2013 for the American Medical Association to finally recognize obesity as a complex chronic disease that requires medical attention.
This has led to greater efforts to improve the health of the nation by promoting healthier eating and encouraging physical exercise.
But even though most people (I hope) are now aware that excess weight can lead to diabetes and heart problems, few people know it’s linked to cancer.
To make sure everyone understands the deadly connection between excess poundage and cancer, just a couple of months ago the Centers for Disease Control and Prevention (CDC) produced a major report on the subject.
I think even well-informed readers will be surprised. . .
Continued below. . .
The Amish Cancer Secret
13 types of cancer associated with body fat
Among adults, overweight is defined as a body mass index (BMI) of 25.0 to 29.9 and obesity as a BMI of 30 or more. BMI is calculated by dividing weight in kilograms by height in meters squared. Or go here to learn how to do it in pounds and inches:
Key findings of the report were as follows:
- more than seven in ten American adults are either overweight or obese
- at least 13 types of cancer are related to excess weight: meningioma (tissue covering brain and spinal cord), multiple myeloma, adenocarcinoma of the esophagus, upper stomach, colorectal, gallbladder, liver, kidney, pancreas, uterus, ovary, breast (postmenopausal)
- over half of Americans are unaware that being overweight increases the risk of cancer
- 55% of cancers diagnosed in women and 24% in men are associated with overweight and obesity
- in 2014, 631,000 Americans received a diagnosis of cancer related to their weight. This represents four out of ten of all diagnosed cancers
- two cases out of three of these occurred in those aged 50 – 74
- between 2005 and 2014, cancers linked with excess weight and obesity rose by 7% (except colorectal which fell by 23%); meanwhile, cancer not associated with weight fell by 13%
So cancers associated with weight are going up while the types of cancer not associated with weight are going down.
The increased risk of cancer in those with a BMI of 30 or more varies according to the target organ. Some examples are: multiple myeloma (20% greater risk), colorectal (30%), gallbladder (60%), pancreatic (1½ fold), kidney, liver, upper stomach (nearly twofold), endometrial cancer (2½ times higher).
These risks continue to climb with increasing levels of obesity. For instance, the endometrial cancer risk with a BMI over 35 rises nearly five times over.
How obesity increases the risk of cancer
The mechanisms linking excess body weight to cancer are not yet well understood. Various sources have offered several theories:
Insulin and insulin-like growth factors (IGFs). These are thought to promote the development of kidney, colon, prostate, endometrial and breast cancer.
Chronic excess insulin decreases IGF binding proteins 1 and 2. This allows more free IGF 1 to circulate, altering the cellular environment. This encourages a number of factors that favor tumor formation.
Sex steroids. Fat tissue promotes increasing levels of aromatase, an enzyme that converts androgens and testosterone – male hormones — to estrogen, the female hormone. Higher amounts of estrogen increase the risk of breast, ovarian, endometrial and possibly other cancers.
Adipokines (e.g. adiponectin and leptin). Adiponectin is the most abundant of these cell-signaling proteins secreted mainly by the visceral fat tissue located around internal organs.
As body weight goes up, levels fall. Since adiponectin inhibits cell growth, falling amounts of it increase the risk of tumor development. Adiponectin has been shown to be anti-inflammatory and anti-angiogenic (prevents growth of unwanted new tumor blood vessels). It’s been found to inhibit tumor growth in animals.
Leptin, on the other hand, stimulates cell growth with increasing body fat.
Other cell growth regulators. Fat cells also have effects both directly and indirectly on other regulators of cell growth. These include rapamycin (a protein involved with cell division and survival that’s active in some types of cancer cells) and AMP-activated protein kinase, an enzyme that helps regulate energy metabolism.
Inflammation. People who are obese suffer chronic low-level inflammation. Over time this can damage DNA and lead to cancer.
Hypoxia, meaning a low level of oxygen, is a common feature of most tumors. A direct role linking hypoxia in fat tissues with cancer has been found in lab studies. In a hypoxic state, the altered cellular environment of fat tissue promotes tumor growth and progression.
BMI – not the best indicator
Another obesity risk factor for cancer was recently discovered by scientists at Michigan State University and published in the journal Oncogene in November, 2017.
The researchers induced cancer in mice and then removed a layer of fat from around the waist. They also took samples of human fat and transplanted them into mice.
They found that a protein called fibroblast growth factor 2 (FGF2) released from fat was responsible for turning normal cells cancerous.
The type of fat that caused the most harm was not the subcutaneous fat that lies just beneath the skin, but visceral “deep” fat stored within the abdominal cavity and around body organs such as the intestines, pancreas and liver. This type of stored fat gives the typical pear body shape seen in so many people these days.
Much larger amounts of FGF2 were produced in the visceral fat, which is more metabolically active and secretes greater amounts of inflammatory chemicals that can trigger the cancer process. In fat secretions that had more of the protein, a greater number of cells already vulnerable to it formed tumors.
Lead author James Bernard said, “Our study suggests that BMI may not be the best indicator. It’s abdominal obesity and even more specifically, levels of a protein called FGF2 that may be a better indicator of the risk of cells becoming cancerous.”
Normal weight yet overfat
As if it isn’t bad enough that 40% of cancers are now linked to being overweight or obese, it gets even worse.
Since BMI is limited as a diagnostic tool because it can’t accurately identify people with excess body fat, and doesn’t specifically measure harmful visceral fat, some scientists believe it is better to consider any excess fat as harmful if it impairs health. This is called overfat.
Under this measure, 91% of American men and 82% of women would be classified as overfat. This means many people whose weight is considered normal by the BMI measure are overfat and therefore at increased risk of disease.
If true, the overfat concept means that NO amount of excess weight is safe. I find it easy to believe. A mere fifty or sixty years ago, most Americans were razor thin compared to the way we look now. That was normal.
The authors of a study published in Frontiers in Public Health in July, 2017 write that “being overfat shares direct links to insulin resistance and chronic inflammation, and to hypertension, dyslipidemia, coronary heart disease, stroke, cancer, Type 2 diabetes, gallbladder disease, osteoarthritis and gout, pulmonary diseases, sleep apnea, and others.”
They suggest the simplest method of considering if someone is overfat is to measure the waist-to-height ratio. Waist measurement should be no more than half your height. So if a person is 5 feet 8 inches tall, measurement around the abdomen (covering the belly button) should be no greater than 34 inches.
A study from the UK and published in Annals of Internal Medicine in June, 2017 measured 42,702 participants. The authors agreed that abdominal obesity is the real health issue.
According to Professor Mark Hamer, who led the study, “Our research does back up the findings of previous smaller scale studies which show normal weight people with central obesity are at increased risk for all-cause mortality.
“It is yet further evidence that even if you are within a ‘healthy’ BMI range but you carry weight around your stomach, your health is still at risk. The message here is that if you do have central obesity, no matter what your BMI, you should take steps to reduce this fat.”
How to lose visceral fat
Not all the news is bad. Experts at Harvard Medical School write that “visceral fat yields fairly easily to exercise and diet.”
To get your weight down, engage in moderately intensive aerobic exercise such as brisk walking, running, swimming or cycling for 30 minutes to an hour a day. Strength training using weights may also help to fight abdominal fat.
As for diet, Americans simply eat far too much. Mindful eating is a novel new approach that’s proven to lose weight. It doesn’t involve calorie or carb counting and you can still eat the foods you love. It’s called Eat Smart, Move More, Weigh Less.
As Dr. Carolyn Dunn from North Carolina State University explains, “Mindfulness is paying attention to your surroundings, being in the present moment.
“Mindful eating is eating with purpose, eating on purpose, eating with awareness, eating without distraction, when eating only eating, not watching television or playing computer games or having any other distractions, and not eating at our desks.”
A recent study of the 15-week program found that, on average, the 42 who took part lost four pounds compared to a control group of 38 who lost only half a pound. After six months, three out of four succeeded in keeping the weight off, while some continued to lose weight. Once the control group joined the program they achieved similar results to the original 42.
Full details of this web-based weight loss program can be found at the Eat Smart, Move More, Weigh Less website (see references).