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An official International Society of Sports Nutrition position paper covering keto diets notes the “ergolytic” effects of keto diets on both high- and low-intensity workouts. Ergolytic is the opposite of ergogenic. Ergogenic means performance-boosting, whereas ergolytic means athletic performance-impairing.

For non-athletes, ketosis may also undermine exercise efforts. Ketosis was correlated with increased feelings of perceived effort and fatigue and mood disturbances during physical activity, suggesting that the ability and desire to maintain sustained exercise might be adversely impacted in individuals adhering to ketogenic diets for weight loss.

I already mentioned the shrinkage of measured muscle size among CrossFit trainees. So, a ketogenic diet may not just blunt the performance of endurance athletics, but strength training as well. Have people do eight weeks of all the standard upper and lower body training protocols—bench press, pull-ups, squats, deadlifts, and, no surprise, you boost muscle mass—unless you’re on a keto diet, in which case there was no significant change in muscle mass after all that effort. Those randomized to the non-ketogenic diet added about three pounds of muscle, whereas the same amount of weightlifting on the keto diet tended to subtract muscle—an average loss of about 3.5 ounces of muscle. How else could you do eight weeks of weights and not gain a single ounce of muscle, but on a ketogenic diet? Even keto diet advocates call bodybuilding on a ketogenic diet an “oxymoron.”

What about bone loss? Sadly, bone fractures are one of the side effects that disproportionately plagues children placed on ketogenic diets, along with growth stunting and kidney stones. Ketogenic diets may cause a steady rate of bone loss, as measured in the spine, presumed to be because ketones are acidic; and so, keto diets can put people in what’s called a “chronic acidotic state.”

Some of the case reports of children on keto diets are truly heart-wrenching. One nine-year-old girl seemed to get it all—osteoporosis, bone fractures, kidney stones—and then she got pancreatitis and died. Pancreatitis can be triggered by having too much fat in your blood. A single high-fat meal can cause a quintupling of the spike in triglycerides in your bloodstream within hours of consumption, which can put you at risk for inflammation of the pancreas. She had a rare genetic disorder called “glucose transporter deficiency syndrome,” where you’re born with a defect in ferrying blood sugar into your brain. This can result in daily seizures starting in infancy, but a ketogenic diet can be used as a way to sneak fuel into their brains. So, a ketogenic diet can be a godsend for the one in 90,000 families stricken with this disorder.

As with anything in medicine, it’s all about risks versus benefits. As many as 30 percent of patients with epilepsy don’t respond to anti-seizure drugs, and the alternatives aren’t pretty, including things like brain surgery. This can mean implanting deep electrodes through the skull, or even removing a lobe of your brain. This can obviously lead to serious side effects. But, so can having seizures every day. So, if a ketogenic diet helps with seizures, the pros can far outweigh the cons.

For those just choosing a diet to lose weight, though, the cost/benefit analysis would really seem to go the other way. Thankfully, you don’t need to mortgage your long-term health for short-term weight loss. We can get the best of both worlds by choosing a healthy diet.

Remember that study that showed that the weight loss after being told to eat the low-carb Atkins diet for a year was almost identical to those told to eat the low-fat Ornish diet? The authors concluded: “This supports the practice of recommending any diet that a patient will adhere to in order to lose weight.” That seems like terrible advice. There are regimens out there, like “The Last Chance Diet which [evidently] consisted of a liquid formula made from leftover byproducts from a slaughterhouse [that] was linked to approximately 60 deaths.” Well, it did promise to change people’s lives. An ensuing failed lawsuit from one widower laid the precedent for the First Amendment protection for deadly diet books.

It’s possible to construct a healthy low-carb diet—or an unhealthy low-fat diet (a diet of cotton candy would be zero fat), but the health effects of a typical low-carb ketogenic diet, like Atkins, are vastly different from a low-fat plant-based diet, like Ornish’s. Not only would they have diametrically opposed effects on cardiovascular risk factors in theory, based on the fiber, saturated fat, and cholesterol contents of their representative meal plans, when actually put to the test, low-carb diets were found to impair artery function. Over time, blood flow to the heart muscle itself is improved on an Ornish-style diet, and diminished on a low-carb diet. Heart disease tends to progress on typical weight-loss diets, actively worsen on low-carb diets, but may be reversed by an Ornish-style diet.

Given that heart disease is the #1 killer of men and women, “recommending any diet that a patient will adhere to in order to lose weight” seems irresponsible. Why not tell people to smoke? Cigarettes can cause weight loss too, as can tuberculosis and a good meth habit, but the goal of weight loss is not to lighten the load for your pallbearers.

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