The principle, on the other hand, makes sense. The bizarrely named "ketone bodies" are actually molecules that serve as the body's natural backup fuel supply when glucose is in short supply. Normally, we only enter ketosis (where ketone bodies accumulate in the blood) when we starve ourselves for several days at a time – not just overnight or by missing a meal. Because the glucose has been depleted, our metabolism shifts to fat-burning, converting stored fat molecules into ketone bodies that can power our muscles and brain. Being in ketosis, then, appears to be an excellent way to burn fat. On the other hand, going days without eating doesn't sound like much fun.
However, it turns out that you don't have to starve yourself to enter ketosis. All you have to do is eliminate carbohydrates from your diet (not just refined carbs, such as sucrose or high fructose corn syrup, but all carbs, including complex carbs and starches too). When the body runs out of glucose, it must enter ketosis because the brain requires either glucose or ketone bodies to survive. So, no matter how much protein or fat you consume, the body must still convert fat to ketone bodies to keep you going.
A ketogenic diet is therefore any diet that causes your metabolism to enter ketosis. And the diets that are currently trending aren't the first or only ones to do so. It's been several decades since the Atkins Diet became popular – and I've seen firsthand the weight loss that some of my friends achieved on Atkins. The Atkins diet is a ketogenic diet because it eliminates carbs and replaces them with protein. The surprising finding was that Atkins followers discovered they were much less hungry than expected, implying that protein calories made you feel fuller for longer. Feeling fuller leads to willingly eating less and, as a result, impressive weight loss.
However, there is no such thing as a free lunch when it comes to dieting (or so I thought). The Atkins diet has side effects, the most concerning of which is the impact on nitrogen balance caused by consuming so much protein. The need to excrete so much excess nitrogen as urea poses a real risk of dehydration and, in the long run, kidney stones.
So, how about the twenty-first-century version? Today, keto replaces carbs with fats rather than protein. A typical Atkins diet consisted of 75 percent protein, 25 percent fat, and 5 percent carbohydrates. In contrast, today's keto diets advocate consuming 75% of one's calories from fat, 25% from protein, and 5% from carbohydrates. Because protein intake is not altered from a typical "balanced" diet, any negative effects from nitrogen imbalance are avoided.
To be honest, I feel 25 years younger.
My concentration and focus also improved noticeably. I'd never had so much energy, and my productivity skyrocketed. Running on the backup batteries (the ketone bodies) is far superior to carbohydrate fueling. Why was that the case? Simply put, because the levels never fall (at least for a chubby person like me, with a boundless supply of internal fat stores to burn). When you eat carbs, the excess is immediately stored as fat, causing blood glucose levels to fall a few hours later, triggering the desire to eat again, but also a sense of declining energy and concentration (that "late afternoon dip" that we "carnivores" recognize only
There were even some unexpected benefits that I discovered. For example, the amount of plaque on my teeth has nearly disappeared (presumably because the plaque bacteria need the dietary carbs to feed off).
What about the disadvantages? Aside from annoying my friends with constant stories of the benefits of a ketogenic diet (the newly converted are always the noisiest street preachers), I could only think of two potential downsides.
The first is purely pragmatic. It's difficult to keep carbs under 5% of total calories. You must check the carbohydrate content of everything you eat, and you will find sneaky carbs in almost everything pre-prepared. Eating out at restaurants becomes difficult, and dining as a guest with friends and family becomes nearly impossible (unless they are also on a ketogenic diet or are incredibly accommodating). As a result, planning and preparing food requires significantly more of your time and resources than it did previously.
Similarly, you must exercise accurate portion control – because the meals are high in fat and have a high calorie density, you may unintentionally consume too many calories. Even the keto diet cannot violate physical laws of the universe, such as the conservation of energy – in order to lose weight, you must consume fewer calories than you require. It simply means that you are having a good time while doing it.
The negative aspect was easier to avoid – but I had been slow to heed the warnings. It is difficult to consume enough fiber while on a ketogenic diet, primarily because most natural fiber sources also contain an excessive amount of available carbohydrate (fiber is typically an insoluble or indigestible carbohydrate polymer, so its unsurprising it naturally co-exists with digestible carbs). The solution is simple: start taking a fiber supplement – 7 or 8 grams per day for me – on the first day you start a ketogenic diet.
At the end of my experiment, I decided to see how eating some carbs after almost a month of being carb-free affected me. Just 50g of carbs in one sitting (equivalent to a very small baked potato) was enough to knock you out of ketosis. Within 3 hours, urinary ketone body levels had dropped to virtually undetectable – hunger had returned, and the "mental fog" had begun to lift.
Of course, it took nearly 72 hours to re-establish "deep" ketosis after only one (in my case, intentional) moment of weakness. Three days of feeling crappy and drained of energy because I was depriving my body of its usual glucose fuel and the backup batteries, the ketone bodies, had yet to kick in. Success on a ketogenic diet, then, clearly necessitates the kind of discipline associated with a Zen master.
This experiment exemplifies the problem that a "balanced" diet causes for a modern human's metabolism. Ketosis takes time to develop but disappears quickly – a phenomenon known as hysteresis. And there are very good evolutionary reasons for this setup: while glucose is a good fuel, it can damage the proteins that make up your cells and tissues. If glucose levels are allowed to rise too high, the consequences may be irreversible (as can happen in diabetes). To avoid this, the body produces insulin as soon as blood glucose levels begin to rise – and insulin limits the amount of glucose in the blood by instructing the liver to convert the excess into fat. At the same time, however, insulin reverses ketosis (which is why ketosis ended so quickly after I ate a baked potato). This ensures that you are not storing fat and burning fat at the same time (which would be a highly inefficient use of food resources).
Evolution tuned our metabolism in prehistory so that we didn't immediately start tucking into our fat stores when food became scarce. Individuals who did this would discover that if a potentially catastrophic food shortage occurred, they would have less fat stored and would thus be the first to succumb. Of course, now that most people in developed countries have unlimited access to calories, this hysteresis that once made us efficient is now making us fat. Every ounce of extra carbohydrate is stored as fat, but those stores are not re-accessed as soon as your glucose runs out. Instead, you're left feeling hungry and tired for a while – and with fast-food fries nearby, it's all too easy to re-fuel with carbs.
Ketosis was once crucial in providing humans with a survival advantage. The science, as well as my personal experience, indicate that it can do the same for people today. If you haven't already, you should give it a try.
