TL;DR: A ketogenic diet is a low-sugar (and sometimes low-total carb) diet where your body gets energy from burning fat and ketone bodies, instead of burning glucose for energy. Higher ketone levels promote metabolic balance by reducing inflammation and stabilizing blood glucose levels. (about 7 min read)

Metabolic tips for getting the most out of a ketogenic diet:

• Really think about your movement goals and adjust protein & total carb intake appropriately.

• Still aim for 25g of fiber/day while reducing total carbs to keep BGLs steady and get enough essential vitamins/minerals.

• Stay hydrated! Breaking down protein to maintain BGLs will produce a lot of uric acid and will stress your body out (canceling out the benefits of reduced inflammation) if you don’t stay hydrated.

What is the “keto” diet? Keto is short for “ketogenesis”. This is a biochemical pathway that produces ketone bodies from the breakdown of fat for energy. Your cells can use ketone bodies instead of glucose for energy when blood glucose is low.*

Higher blood ketone levels help reduce inflammation and promote metabolic balance by stabilizing blood glucose levels. Ketone bodies, specifically the molecule beta-hydroxybutyrate, will inhibit a protein complex in cells and reduce inflammation by stopping immune cells from overreacting. This has been shown to be really beneficial to everyone in general, but especially useful for people with immune conditions, treatment-resistant epilepsy, systemic inflammation from metabolic disorders (eg. Type 2 Diabetes or gout, amongst others), some types of migraines, and other neurological disorders.

You can maintain steady blood glucose levels without eating simple carbohydrates. Your liver will produce glucose from other molecules (protein and fiber) if your BGLs get too low. You need to eat enough protein and fiber for your liver to do this. Someone could maintain steady BGLs by eating just enough protein alone to allow their liver to do gluconeogenesis, and skipping all carbs completely, if they wanted to. This is called the “ketogenic diet” and it’s often followed by people with immune disorders, who are dealing with treatment-resistant epilepsy or migraines, or who are trying to reverse Type 2 diabetes/pre-diabetes.

How much do you have to reduce total carb intake to maintain ketogenesis? If someone is really following a keto diet with the intention of raising their blood ketone levels as much as possible, they usually do this by limiting all carbohydrates (fiber and sugar) and also keeping their dietary protein levels down, since dietary proteins can also raise BGLs (your liver will use protein to make glucose via gluconeogenesis; you don’t store protein on your body). It’s a real balancing act between getting enough nutrition (essential fats, essential amino acids from protein, essential vitamins/minerals from fruits & vegetables) and what type of movement someone is routinely doing that will determine how much sugar, fiber, or protein someone can eat and maintain ketogenesis.

Anytime your body burns through your glycogen stores and your BGLs start to drop, your liver burns fat and put ketone bodies into the blood. So how many total carbs someone eats will depend on the type of movement they do. The most common advice I’ve seen thrown around is that you need to eat less than 50g, or even as low as 25g, of total carbs in order to maintain ketogenesis. A diet this low in total carbohydrates is probably leaving out fiber (we’d like to be getting 25g of fiber a day) and comes at the cost of moving fast. (I’ll discuss “slow” vs “fast” energy and how they relate to how fast we run/cycle in other posts).

If you’re new to a “keto” diet, it may take a few weeks for your liver to switch biochemical programs and start producing a measurable amount of ketone bodies. However, once you’re there, whether or not you maintain ketogenesis depends on what else you’re doing. I ate 100-150g of carbs/day while training for a half-marathon and maintained ketogenesis (2-5x more than “internet experts” said was possible! I measured them to answer this question for a friend). So really, the total carbs someone can eat depends on what type of movement they’re doing.

You need to drink more water when maintaining ketogenesis. Because your liver is now breaking down proteins to maintain stable BGLs, you will make more uric acid. Uric acid will cause inflammation if it builds up in a tissue (gout) and can damage your kidneys. You need to drink more water so you pee the uric acid out, or you’ll undo the positive effects of the ketone bodies with the negative effects of the uric acid.

Is the ketogenic (keto) diet right for you? That depends on other factors, like some hormone stuff, if you do endurance athletic stuff, and if you have a condition where you really want to limit inflammation. The trade-off with a keto diet (that lacks fiber) is that you do maintain steady BGLs and reduce inflammation, but you also make it easier to miss out on some essential vitamins/minerals that are found in fruits and vegetables.

A no-fiber keto diet will also lower the diversity of your gut microbiome (this is still being studied, so we know the gut microbiome changes but we don’t understand too many details right now). This can have long-term health implications, or not. More research on the gut microbes and the keto diet is needed. The changes in the gut microbes may make things wacky if/when you do introduce carbs back into your diet, especially if you make a drastic dietary change and you add a lot of simple carbs back at once.

Can you have the best of both worlds by eating fiber AND maintaining ketogenesis? Yes. Yes, you can. (Some people using keto diets to deal with medical conditions may still want to keep total carbs as low as possible if it’s more helpful for their condition than getting the full 25g of fiber would be.)

Fiber (a complex, “slow” carb) is treated differently by your body than simple carbs. A fast influx of simple carbs (sugar) will cause your liver to stop doing ketogenesis and start dealing with the sugar. However, a slow or minimal rise in BGLs won’t cause your liver to switch. Adding foods to your diet that are high in fiber but low in “other carbs” can allow your body to maintain high ketone levels while also getting extra vitamins/minerals from those high-fiber, low-sugar foods and help your gut maintain a healthy & diverse microbiome. Again, what a “minimal” rise in BGLs is for you is going to be determined by the type of movement you routinely do.

Foods* like avocadoes (15g fiber + 5g simple carbs for medium avocado), raspberries (8g fiber + 7g simple carbs in 1 cup raspberries), flax seeds (3g fiber +0g simple carbs in 1 tbsp flax seeds, cauliflower (2.5g fiber + 3g simple carbs in 1 cup cauliflower), or cabbage (2g fiber + 3g simple carbs in 1 cup of cabbage) are great options for people looking to keep their simple carb intake low without missing on vitamins/minerals or gut health.

Metabolic tips for getting the most out of a ketogenic diet:

• Really think about your movement goals and adjust protein & total carb intake appropriately.

• Still aim for 25g of fiber/day while reducing total carbs to keep BGLs steady and get enough essential vitamins/minerals.

• Stay hydrated! Breaking down protein to maintain BGLs will produce a lot of uric acid and will stress your body out (canceling out the benefits of reduced inflammation) if you don’t stay hydrated.

Youm, Y.H., et al. (2015) The ketone metabolite beta-hydroxybutyrate blocks NLRP3 inflammasome-mediated inflammatory disease.

Richards, J.L., et al. (2016) Dietary metabolites and the gut microbiota: an alternative approach to control inflammatory and autoimmune diseases. Clinical and Translational Immunology.

*Type 1 Diabetics also have to make sure that their liver isn’t tricked into producing too many ketone bodies because will lower their blood pH and lead to ketoacidosis, a very serious condition. This occurs when there is too little insulin in the body, and doesn’t usually happen to non-Type 1 Diabetics even if they eat a low-sugar or ketogenic diet. This is because other foods, including protein and alcohol, will cause the pancreas to release some insulin. As long as some insulin is released, non-Type 1 Diabetics will avoid ketoacidosis.

**I put together a reference guide of foods that are good sources. It lists the serving size, the grams of fiber, and the grams of “other carbs” so you can make choices that fit your lifestyle and taste preferences. The guide also includes a comparison of some common snacks vs healthier alternatives. Like, Honey Nut Cheerios is the most common breakfast cereal and has 3g of fiber + 12g of added sugar. This can be switched out for cinnamon-vanilla Kashi Go which has 7g of fiber and 0g of added sugar. Boom. You’re already over a quarter of the way to your 25g of fiber/day. Sign up for the newsletter to get the “fiber guide”.