Activity, Diet, Obesity, and Knee Osteoarthritis: Interesting Relationships

Are we out of shape, addicted to sugar, and possessed of broken-down knees? Recent research implies these associations, and it stimulates within me great interest as well as concern.


A study, published in The Proceedings of the National Academy of Sciences in August 2017 by researchers from Harvard, reported that Americans today are twice as likely to have knee osteoarthritis as those before World War II. Examining over 2,000 skeletons spanning a 6,000 year period, the researchers were able to identify the joint damage, known as eburnation, across both genders and all age groups. This paper’s conclusion was that OA of the knee is not necessarily a condition of the aging process, as we have previously assumed.


Investigators at the Center for Osteoarthritis Research at Tufts University School of Medicine in Boston have recently identified 4 factors that accelerate the progression of Knee OA in Americans. These are age, body mass index (BMI), blood glucose levels, and tibiofemoral (knee) joint alignment. Additionally, they suggested that sports participation, which is a fairly recent phenomenon in human existence, also plays a role in OA progression when injuries are involved. The researchers hypothesized that the injuries can degrade the joint surfaces and biomechanics, depending on the specific damage, thus propagating enhanced OA. There is also some consensus that youth sports participation, at least that resulting in knee injury, may be contributing to earlier onset of knee OA than in centuries past.


A study published in the November issue of Frontiers of Public Health identified 91% of American adults and 69% of children as being overfat, which the authors define as having enough excess bodyfat to impair one’s cardiovascular, metabolic, or physical health. Using new data from the Centers for Disease Control and Prevention (CDC), authors Phil Maffetone and Paul Larsen suggest that this weight gain epidemic is largely related to the excess refined carbohydrates and sugars in our current food supply. And they also state that this is occurring despite data that shows we Americans are exercising at higher levels than ever before.


So what gives? Are we all a bunch of overweight, over-exercising, glucose-burning sugar addicts with worn-out knees? I’m not sure we can definitively say that but I’ll pontificate briefly on some of these relationships. Our increasing national weight problem is multifactorial, but it is powerfully linked to two things: less total activity and increased processed carbohydrate consumption.


By less total activity I’m referring to our general increase in sedentarism. Desk jobs, vehicular travel, and many other facets of modern life take from us our natural, ancestral pattern of nearly constant movement throughout the day. This is different from an exercise workout, and according to this author as well as much current research, a critical necessity for optimal biologic function. While outliers exist, we just are not as generally active, as a population on the whole, as we historically had been prior to WWII. Newer science supports the concept that our weight maintenance is a product of optimal metabolic and hormonal function, and this is highly dependent upon high levels of general activity. It is not quite as simple as “how many calories can you burn”, as a properly functioning metabolism can regulate fat storage regardless of whether one does a large exercise workout or not. The newer literature identifies a phenomenon known as“active couch potato syndrome”, an example of which would be how a lunchtime workout won’t offset the deleterious effects of a day’s worth of sitting.


Increased processed carbohydrate consumption is self-explanatory. Based on decades of research examining glycemic index and glycemic load, we now have a fairly clear picture that most processed carbs (sugar, flour, corn starch, etc. – and these ingredients are the major constituents of most packaged food “products”) rapidly elevate blood glucose levels, lead to insulin resistance, weight gain, hormonal dysregulation, and disease. And numerous studies support the addictive nature of processed carbs (all of which becomes “sugar” in the body, whether it’s a gummy bear or a slice of whole wheat bread) that has been proven to be as powerful as nicotine and more so than cocaine!


So we sit around more and eat too much sugar, whether it’s intentional or inadvertent. We get fatter and thus heavier and the simple physics of this results in more wear and tear on our knees.


Then we add the proverbial insult to injury by losing the ideal alignment in our lower extremities (yes, the posture of the legs can and should be trained – see your friendly neighborhood physical therapist!). This causes increased interfacial wear on our articular cartilage, of which we essentially get one dose per lifespan and have limited, if any, capacity to regenerate.


And while I’m on the bad news (there will be some good news coming up), this demon known as sugar gets and deserves yet another bad rap. Sugar causes inflammation! Sure, a little fruit and veggie for the moderately active person is good, providing water, fiber, micronutrients, and a limited amount of slower-digesting carbs for energy, but higher levels are bad. Very bad. The literal wheelbarrow load, or the equivalent of several of them, of sugar consumed via processed carbs in the typical American diet each year, leads to rampant glycation and oxidative stress in our bodies. This has been proven to increase inflammation system-wide, especially in our joints.


We need some additional research done in this area for sure. The data is intriguing but regression analysis and multiple analysis of variance are indicated to ferret out more definitive information about the association between blood glucose levels and knee OA. Is a high blood glucose level almost a guarantee, if prolonged, that your knees are eroding? Or is it primarily that eating too much sugar makes us fat and just overloads the knees? I’m going to suggest that that both premises are probably valid, with those effects being both variable among individuals and dynamic within an individual’s lifespan.


And where does this statistic about more exercise not helping the problems of obesity or knee OA fit in? A fitting answer to this question is quite long, and in fact will be featured in an upcoming book I’m publishing in December. But since there is no need to keep you in suspense, I’ll mention that weight loss is WAY more effective when lifting a fork (or not lifting!) than lifting a dumbbell. Nutritional intake is simply a more powerful stimulator of health and weight loss than is a simple workout. Not that exercise isn’t valuable…it is, but we (not every reader here but most Americans on average) tend to approach it incorrectly. We are often not consistent enough, and/or we tend to use too much moderately high intensity training in chronic patterns. I imagine that these statements will either interest, or enrage you, or both. Feel free to comment, email me, or read “The Lifetime Body: How to Make Your Body Last a Lifetime” when it comes out at Christmastime.


OK…now for the good news. Eat less sugar. Sit less. Move (easily) a little more. Work on strength and alignment of your knees with a few simple exercises for just minutes per week. Enjoy your exercise, but be careful not to get injured or exhausted. These habits can help you to lose weight, improve your health, and reduce your risk of knee OA. As one of my mentor’s once taught me, “You want your joints to outlive you, not the other way around.”

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