Obesity Series: Part 2

You may have heard the expression “knowledge is power.” Well – today – we’re going to give you more power to control your diet and lifestyle – by giving you the facts. Welcome to the Nutrition Facts podcast. I’m your host – Dr. Michael Greger.

Today, it’s Part 2 in our series on obesity. And we start out by looking for an alternative to knee replacement surgery that treats the cause and offers beneficial side effects.

The largest study in history on the health effects of being overweight, analyzing data from more than 50 million people from nearly 200 countries, found that excess body weight accounts for the premature deaths of about 4 million people every year. Most of these deaths are from heart disease, but the researchers found “convincing” or “probable” evidence linking obesity to twenty different disorders—a veritable alphabet soup of potential health concerns.

In the ABCs of health consequences, A is for arthritis. Obesity can make rheumatoid arthritis worse, and increase the risk of another inflammatory joint disease, the so-called “disease of kings,” gout. The most common joint disease in the world, though, is osteoarthritis, and obesity may be the main modifiable risk factor.

Osteoarthritis develops when the cushioning-cartilage-lining of joints breaks down faster than your body can build it back up. The knees are the most commonly affected, leading to the assumption that the relation to obesity was simply the excess wear and tear from the added load on the joints. But non-weight-bearing joints like the hands and wrists can also be affected, suggesting the link isn’t purely mechanical. Obesity-related dyslipidemia may be playing a role, with elevations in the amounts of triglycerides, fat, and cholesterol in the blood aggravating inflammation in the joints, just like cholesterol can aggravate the inflammation in your artery walls.

Osteoarthritis sufferers not only have higher cholesterol levels in the blood; they have higher cholesterol levels within their joints, both in aspirated joint fluid and in the cartilage itself. Drip cholesterol on human cartilage in a petri dish, and you can worsen the inflammatory degeneration, helping to explain why the higher people’s cholesterol, the worse their disease. Cholesterol-lowering statin drugs may both help prevent and treat osteoarthritis, as can a cholesterol-lowering diet. A healthy enough plant-based diet may offer the best of both worlds, dropping cholesterol as much as a starting dose of a statin drug—within a single week—and only has good side effects, such as lowering blood pressure and facilitating weight loss.

Even just losing about a pound a year over the span of a decade may decrease the odds of developing osteoarthritis by more than 50 percent. Weight reduction may even obviate the need for knee-replacement surgery. Obese osteoarthritis sufferers randomized to lose weight improved their knee function as much as those going through surgery––within just eight weeks. The researchers concluded that losing 20 pounds of fat “might be regarded as an alternative to knee replacement.”

Isn’t it easier to just get your knees replaced than lose 20 pounds? Rarely discussed is the fact that nearly 1 in 200 knee replacement patients die within 90 days of surgery. Given the extreme popularity of this operation—about 700,000 a year in the U.S.—an orthopedics journal editor suggested that “people considering this operation are inadequately attuned to the possibility that it may kill them”––arguably, the “single most salient fact” to share with a patient considering the operation. An orthopedic surgeon responded to questioning whether patients should be told about the chance the operation may kill them: “To me, the real question is whether this knowledge will help the patient. Will it add to the anxiety of the already-anxious patient, perhaps to the point of denying that patient a helpful operation? Or will this knowledge motivate a less-handicapped patient to stick to a diet and physical activity regime? Ultimately, then, the question boils down to the surgeon’s judgment.”

Even among the vast majority who survive the surgery, approximately one in five knee replacement patients describe being unsatisfied with the outcome. Weight loss with a healthy diet, on the other hand, may offer a nonsurgical alternative that instead treats the cause, and offers only beneficial side effects.

In our next story we examine how losing weight can reduce sciatica, hypertension, and cancer risk, and reverse type 2 diabetes.

In the ABCs of the health consequences of obesity, if A is for Arthritis, as I laid out in my last video, then B is for Back Pain. Being overweight is not just a risk factor for low back pain, but also sciatica, a radiating nerve pain, and lumbar disc degeneration, and disc herniation. Like in the arthritis story, this may similarly be due to a combination of the hefty load, high cholesterol, and inflammation associated with being overweight. Why cholesterol? Autopsy studies and angiography studies show that the lumbar arteries that feed the spine can get clogged off with atherosclerosis and starve the discs in your lower back.

B is also for Blood Pressure. Excess visceral fat—excess internal abdominal fat—can physically compress your kidneys. The increased pressure can effectively squeeze sodium back into your bloodstream, increasing your blood pressure. Together, the combination of obesity and hypertension can have “disastrous health implications.” But the good news is that even just a few pounds of weight loss can help take the pressure off. Losing weight has been described as a “vital strategy for controlling hypertension.” Losing around nine pounds may lower blood pressure about as much as cutting salt intake approximately in half.

C is for Cancer. As many as three-quarters of people surveyed were evidently unaware of the link between obesity and cancer, when, in fact, based on a comprehensive review of a thousand studies, excess body fat raises the risk of most cancers, including esophageal cancer, stomach cancer, colorectal cancer, liver cancer, gallbladder cancer, pancreatic cancer, breast cancer, uterine cancer, ovarian cancer, kidney cancer, brain cancer, thyroid cancer, and bone marrow cancer (multiple myeloma). It could be the chronic inflammation of obesity. It could be the high insulin levels due to insulin resistance. (Besides controlling blood sugars, insulin is a potent growth factor that can promote tumor growth.) In women, it could also be the excess estrogen.

After the ovaries shut down at menopause, fat takes over as the principal site of estrogen production. That’s why obese women have up to nearly twice the estrogen levels circulating in their bloodstream, which is associated with increased risk of developing—and dying from—breast cancer. The data on prostate cancer isn’t as strong, though obesity is associated with increased risk of invasive penis cancer.

One of the reasons we’re confident the link between obesity and cancer is cause-and-effect, and not just an indirect consequence of eating poorly, is that when people lose weight—even just through bariatric surgery—their overall risk of cancer goes down. Those experiencing a sustained weight loss of about 40 pounds after surgery went on to develop around a third fewer cancers over about the subsequent decade than the nonsurgical control group of matched individuals that continued to slowly gain weight over time. The exception, though, is colorectal cancer.

Colon and rectal cancer appears to be the only malignancy for which the risk goes up after obesity surgery. After bariatric surgery, the rate of rectal cancer death may triple. The rearrangement of anatomy involved in one of the most common surgeries—Roux-en-Y gastric bypass—is thought to increase bile acid exposure along the intestinal lining. This causes sustained pro-inflammatory changes even years after the procedure, which is thought responsible for the increased cancer risk. In contrast, losing weight by dietary means has the potential to decrease obesity-related cancer risk across the board.

D is for Diabetes. As laid out in a consensus statement from the International Diabetes Federation, obesity is considered the single most important risk factor for the development of type 2 diabetes, the leading cause of kidney failure, the leading cause of lower-limb amputations, and the leading cause of adult-onset blindness. Ironically, many of the leading drugs used to treat diabetes (including insulin itself) actually cause further weight gain, creating a vicious cycle. So again, using lifestyle medicine to instead treat the underlying cause is not only safer, simpler, and cheaper, but also can be most effective.

Finally today, –we look at how weight loss can decrease dementia risk and improve mental performance and infertility.

In the ABCs of health consequences of obesity, if A is for Arthritis, and B is for Back Pain and Blood Pressure, C is for Cancer, and D is Diabetes, then E is for Encephalopathy.

Encephalopathy means brain disease. There’s consistent data linking obesity in middle age to higher risk of dementia later in life. Overweight individuals have about a third higher risk, and those who are obese in mid-life seem to have about 90 percent greater risk of becoming demented. The risk isn’t just limited to future dysfunction, though. People with excess body weight don’t appear to think as clearly at any age.

Obese individuals show broad impairments in what are called executive functions of the brain, such as working memory, decision-making, planning, cognitive flexibility, and verbal fluency. These “play a critical role in everyday life.”

People may think about their obesity and the resulting stigma they experience as much as five times an hour, but the cognitive deficits do not appear to arise just from distraction; there are structural brain differences between normal weight and overweight individuals.

A review entitled “Does the brain shrink as the waist expands?” noted gray matter atrophy across all ages among those carrying excess body fat. This reduced brain volume has then been correlated with the lower executive function. Compromised integrity of the rest of the brain—the white matter—suggests accelerated brain aging, even in young adults and children with obesity. Cognitive deficits in young populations suggest it’s something about the obesity itself that’s affecting brain function, rather than a later clinical consequence, such as high blood pressure. Purported mechanisms for this executive dysfunction include obesity-related inflammation and oxidative stress.

So, does weight loss improve cognitive function? Based on a meta-analysis of 20 studies, mental performance across a variety of domains can be significantly improved with even modest weight loss, though no studies have yet to be done to determine if this then translates into a normalization of Alzheimer’s disease risk.

F is for Fertility, or rather failed fertility. Overweight couples struggling to have children “should be educated on the detrimental effects of fatness,” one meta-analysis concluded, as weight loss is associated with an improvement in pregnancy rates among infertile women. Men also may suffer impaired fertility. The heavier a man is, the greater their risk of having a low sperm count or being completely sterile. This may in part be due to the effects of excess body fat on testosterone levels.

Fat isn’t just the primary site of estrogen production in postmenopausal women, but in men as well. There’s an enzyme in body fat that actually converts testosterone into estrogen. Men even going from obese to just overweight could potentially raise testosterone levels in their blood 13 percent.

A more dramatic cause of infertility in obese men is called “hidden penis.” Also referred to in the medical literature as buried penis, concealed penis, or inconspicuous penis, it occurs when excess fat in the pubic area subsumes the male member (since the base is attached internally to the pubic bone). It’s also called trapped penis, because the moist enfolding skin surfaces can result in a chronic inflammatory dermatitis leading to scarring, requiring a surgical intervention. So, “F” may also stand for Free Willy.

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