Here in Part IV of the Sock Doc Essential Guide to Carbohydrates, I’m going to discuss the hot topic of a ketogenic diet for athletes. Ketosis is a metabolic state where the liver takes fat and proteins and produces molecules called ketone bodies to use for energy. Ketosis allows a starving person to survive for days (or even months). Some athletes see great improvements in their health and fitness when they’re in a ketogenic state, while others just feel miserable. So is a ketogenic diet right for you?
Ketogenic Diet and Your Brain
Your brain is approximately 2% of your body mass, though it requires approximately 20% of your basal metabolic rate—or more if you’re a thinker. That’s not necessarily a joke, believe it or not. Different parts of your brain use different amounts of glucose, and nearly twice as much later in the day than in the morning. If you’re using your brain to solve problems and work hard mentally throughout the day, you’ll need to fuel your head more. If you’re working more on motor control (say, a skill involving precision or balance), then you’ll use less glucose. Personally, I can attest to how much more energy my brain uses when mentally challenged. When I’m treating patients in my office, often dealing with complex problems and biochemical pathways, I can’t go as long without eating some carbs than if I were outside training most of the day. Even though I’m using more energy exercising for perhaps six to eight hours, I feel more fatigued when using more of my brainpower for less time.
Though our brains run off glucose and not fat, they can also run off of ketones as an alternative fuel source. Those who promote ketogenic diets tend to note the fact that an increase in ketones improves the recovery and repair of neurons and increases the inhibitory neurotransmitter GABA. (GABA chills you out and helps you sleep. It’s also the main neurotransmitter that sleep medications and anti-anxiety drugs affect.) Due to the effect of ketones on the brain, a ketogenic diet can really help those with epileptic seizures. Of course, ketosis means you’re burning way more fat (in the form of ketones) for energy than sugar, and for the most part, that’s usually a good thing.
You won’t venture into a dangerous diabetic ketosis level as long as you’re producing even just a little amount of insulin. So as long as you’re not a type 1 or pancreas-about-to-fail type 2 diabetic, there is nothing to worry about. But to stay in a keto-adaption state, you typically need to eat less than 50 grams of carbs per day, if not much less than that; it’s not an easy feat. In this state, the body relies on fat rather than glycogen, and the brain relies on ketones rather than glucose.
People wishing to achieve ketosis also can’t consume too much protein. This usually means no more than 150g a day. Protein can be converted to glycogen, and as you learned earlier in Part I, this protein can also be used to make glucose, which would throw you out of ketosis.
Ketones vs. Glucose: Know When to Say When
So should you try to achieve this ketogenic state? I think it’s unnecessary for most, but some people need to do it at least temporarily to get their body out of insulin resistance. Again, like most things, it’s very individualized. If you’re severely insulin resistant, then this might be your way out of it and on the road to health again. Overall, most people could do better (meaning become more fit and healthy) by eating fewer carbs. But some people tend to go to the extreme and fear carbs when they don’t need to. Most people also fear insulin since everything we read today about obesity, cancer, and pretty much any disease talks about inflammation and insulin. But don’t forget it’s all about making just the right amount. Insulin isn’t a bad guy, just too much of it is. If you don’t make insulin when you should, you’re actually in a more dire situation than making too much and becoming insulin resistant.
It typically takes two to three weeks to really shift your body over to fat from using sugar as a primary fuel source, and this is with a very low-carb, high-fat diet. Often, just tweaking your diet a little won’t do the job to make the shift. You have to go to the more extreme for a few weeks, and then you can add in some carbs after that and see how you react to them, mentally and physically. The nice thing about shifting your body from sugar to fat burning is that you also won’t convert back to being a sugar-burner if you eat too many carbs for a short period of time. I put many of my patients on a carbohydrate elimination diet to get them headed in the right direction.
Whether you want to be in ketosis or not is up to you, but you should be able to go days without any carbs (other than veggies) in your diet. Complex carbs should typically only be consumed when you’re training hard or long, or when you just want to eat them because you want something like pizza, a dessert, or whatever you’re into.
Remember, even if you’re only eating around 2,000 calories a day, then 100g of carbs is only 20% of your diet. Hopefully, you’re getting the same amount of protein, and that leaves the fat around 60%, which is around 130–135 grams of fat. (Fat is 9 calories per gram; protein and carbs are each 4 calories per gram.) If you’re training hard, you’ll want some more carbs. No, actually, you’ll need some carbs. If you’re trying to go on a ketogenic diet, then good luck training hard or at any moderate-to-high intensity for a prolonged period. You will feel like hell, and you won’t last very long. So if you’re going to try such a diet, do it in the offseason when you’re building a solid aerobic base or when you’re in a recovery period from training hard or racing.
On a clinical note, I’ve never seen a patient do well staying in ketosis for more than a month or six weeks, max. I recently saw a young 30-year-old athlete who has been in ketosis (verifying via blood testing daily) for three months. His pain and health ailments were a result of being in a ketogenic state for so long. The diet initially helped him progress physically and mentally, but it eventually turned on him without him realizing. He needed some sugars/carbohydrates and some insulin in his body—less is not always better. I see this same situation every time someone tries to stay on a strict ketogenic diet with no reprieve for weeks and then months. So if you’re going to go keto, take a break every couple of weeks or so and see how you feel and function in and out of ketosis.
