Let’s talk about a keto side effect that may not be so sexy: constipation. “Many of the richest sources of fiber, like beans, fruit, and whole grains are restricted on the ketogenic diet,” says Clark. “As a result, ketogenic eaters miss out on the benefits of fiber-rich diet such as regular laxation and microbiome support. The microbiome has been implicated in everything from immune function to mental health.” Indeed, in a long-term study in the Journal of Pediatrics in April 2015, constipation was noted as a very common side effect in children receiving ketogenic diets for epilepsy treatment.
3 years ago I was 500 pounds at my absolute worst. Went through a traumatic experience when I was 17 and afterwards the weight just seemed to add on over the years. I'd always been a big guy but it got really bad. Decided to start the keto diet after looking into healthier lifestyles and fast forward two years later (with intermittent fasting and gym training) I had lost 260 pounds. I kept under 1200 calories a day and the best feeling was not constantly being hungry. The last year has been more of a maintenance but with keto cycling.
The ketogenic diet is calculated by a dietitian for each child. Age, weight, activity levels, culture, and food preferences all affect the meal plan. First, the energy requirements are set at 80–90% of the recommended daily amounts (RDA) for the child's age (the high-fat diet requires less energy to process than a typical high-carbohydrate diet). Highly active children or those with muscle spasticity require more food energy than this; immobile children require less. The ketogenic ratio of the diet compares the weight of fat to the combined weight of carbohydrate and protein. This is typically 4:1, but children who are younger than 18 months, older than 12 years, or who are obese may be started on a 3:1 ratio. Fat is energy-rich, with 9 kcal/g (38 kJ/g) compared to 4 kcal/g (17 kJ/g) for carbohydrate or protein, so portions on the ketogenic diet are smaller than normal. The quantity of fat in the diet can be calculated from the overall energy requirements and the chosen ketogenic ratio. Next, the protein levels are set to allow for growth and body maintenance, and are around 1 g protein for each kg of body weight. Lastly, the amount of carbohydrate is set according to what allowance is left while maintaining the chosen ratio. Any carbohydrate in medications or supplements must be subtracted from this allowance. The total daily amount of fat, protein, and carbohydrate is then evenly divided across the meals.[37]
So how does this work? A quick run-through: The first tip was to eat low carb. This is because a low-carb diet lowers your levels of the fat-storing hormone insulin, allowing your fat deposits to shrink and release their stored energy. This tends to cause you to want to consume less calories than you expend – without hunger – and lose weight. Several of the tips mentioned above are about fine-tuning your diet to better this effect.
First, decide if you need to check ketones.  Amy Berger of Tuit Nutrition has a great post here to help you decide.  If, after reading that, you still want to check your ketone levels, there are several ways to check them. You can buy Bayer ketone stix, and check the levels of ketones in your urine. Or you can use a blood ketone meter.  The Precision Xtra has been the one to use until just recently. The problem is that this meter is hard to find, as the manufacturer Abbott keeps changing the name. The strips are even harder to find and buy.
The first modern study of fasting as a treatment for epilepsy was in France in 1911.[12] Twenty epilepsy patients of all ages were "detoxified" by consuming a low-calorie vegetarian diet, combined with periods of fasting and purging. Two benefited enormously, but most failed to maintain compliance with the imposed restrictions. The diet improved the patients' mental capabilities, in contrast to their medication, potassium bromide, which dulled the mind.[13]

Question: I have recently done my 23&me DNA test and have also put my info into AthletiGen. I’m curious about your thoughts about high fat/low carb diet in context of this info. My test says I am ‘2x more likely to loose weight on a low fat diet’, and that I have ‘normal sensitivity to weight gain due to saturated fat intake/and unsaturated fat intake’, & ‘likely to eat normal amounts of carbs’! All interesting but in the ketosis context, I took this to mean that eating high fat/low carb would not be of greatest benefit to me?! (I have tried getting into ketosis prior to all the new supps, for about 3 months, and I couldn’t get in to it (tested w/ blood finger prick) and didn’t feel great). Which leads me to wonder what Macro ratio would be best, as I’m also a endo-meso)!
You state that many athletes and very active people could benefit from 100-200g of carbs a day, and be back in ketosis in a few hours. Any particulars on which kind of activities or say how long/many training sessions would benefit from this to balance hormones. I train mma 3-4 days a week and also do lots of hiit and strength training as well. Just trying to see if this is a situation where i would benefit from your suggestions. Thanks!
Bulk buy and cook. If you’re someone who doesn’t like to spend a lot of time in the kitchen, this is the best of both worlds. Buying your food at bulk (specifically from wholesalers) can reduce the cost per pound tremendously. Plus, you can make ahead food (bulk cook chicken thighs for pre-made meat, or cook entire meals) that are used as leftovers, so you spend less time cooking.
Can’t get enough of avocados? You now have a great excuse to eat more of them. A ½-cup serving of the creamy fruit has almost 12 g of fat and only 2.6 g of net carbs. Avocados are also low in calories (about 138 for the same serving), making them an ideal snack in between meals. One serving also has about 6.4 g of dietary fiber (25.6 percent daily value, or DV), 404 milligrams (mg) of potassium (8.6 percent DV), and only 2.8 g of sugar. Try topping your salad with cubed avocado for a keto-friendly lunch.
Another possible nutrient deficiency: potassium, a mineral important for both electrolyte balance and blood pressure control, notes MedlinePlus. “Inadequate intake of potassium is likely when consumption of fruits and starchy vegetables are decreased,” says Asche. She recommends adding lower-carb sources of potassium to the diet, including avocado and spinach — as well as lower-carb sources of fiber, such as chia seeds and flaxseed (be sure to enjoy ground for the best health benefits).
A systematic review in 2018 looked at 16 studies on the ketogenic diet in adults. It concluded that the treatment was becoming more popular for that group of patients, that the efficacy in adults was similar to children, the side effects relatively mild. However, many patients gave up with the diet, for various reasons, and the quality of evidence inferior to studies on children. Health issues include high levels of low-density lipoprotein, high total cholesterol, and weight loss.[24] 

Great article! As someone who just started a “ketogenic diet” two weeks ago, I am opting to hold off on using ketone supplements for the following reason. You state how “Keto-adaptation occurs when you have shifted your metabolism to relying on fat-based sources, instead of glucose (sugar) sources, as your primary source of fuel.” If the goal is to “switch” our body’s energy supply to ketones and one uses supplemental ketones, how do they really ever know if their body has successfully accomplished this goal if they are using supplemental ketones? Aren’t they getting a false sense of ketosis if their blood or breath tests show them above 0.5 millimolar through the use of the supplements? I understand that it may take me longer to reach ketosis naturally but I guess I see it was worth it to truly reap all of the benefits that you outline in your article.
I just discovered your site and have been thoroughly enjoying many of the articles and appreciate that you get so in depth in your explanations. I’m in my late 40’s and, while not an extreme endurance athlete, I am moderately active with 18-20 mile rides 3x a week as well as some boxing and body weight resistance (push up, pull up, etc) mixed in. I’ve generally been paleo and stick to quality macros for the most part (grass fed meats/dairy, organic veg and oils) and zero supplements. I recently started following keto (after reading this article) about 10 days ago and things seem good thus far. I do, however, want to avoid any of the negative side effects you mention and also not lose any lean muscle. I’m currently about 174 lbs, 5’8″ and about 19% bodyfat – I’m taking in about 95g protein, 130g fat and <20g net carbs. I'm eating all quality – wild salmon, grass fed beef, pastured eggs, coconut oil, Brain Octane and Grass fed butter in coffee, sardines, etc. With a smattering of organic veg, but it seems real easy to bust through the carb barrier. *I'M ALSO TAKING KETOCANA PRE-WORKOUT* and I notice this is keeping me going throughout a ride or the gym.

There’s not enough of it to matter in coconut oil, it tastes bad, and it often results in stomach/gastric upset, but it does get converted quickly into ketones. If your MCT oil brand of choice makes your throat burn or has a weird flavor, one reason may be that the distillation did not remove enough of the C6. There are other reasons this can happen too, discussed below.


A study with an intent-to-treat prospective design was published in 1998 by a team from the Johns Hopkins Hospital[20] and followed-up by a report published in 2001.[21] As with most studies of the ketogenic diet, no control group (patients who did not receive the treatment) was used. The study enrolled 150 children. After three months, 83% of them were still on the diet, 26% had experienced a good reduction in seizures, 31% had had an excellent reduction, and 3% were seizure-free.[Note 7] At 12 months, 55% were still on the diet, 23% had a good response, 20% had an excellent response, and 7% were seizure-free. Those who had discontinued the diet by this stage did so because it was ineffective, too restrictive, or due to illness, and most of those who remained were benefiting from it. The percentage of those still on the diet at two, three, and four years was 39%, 20%, and 12%, respectively. During this period, the most common reason for discontinuing the diet was because the children had become seizure-free or significantly better. At four years, 16% of the original 150 children had a good reduction in seizure frequency, 14% had an excellent reduction, and 13% were seizure-free, though these figures include many who were no longer on the diet. Those remaining on the diet after this duration were typically not seizure-free, but had had an excellent response.[21][22]
^ Lockyer, Christina (1991). "Body composition of the sperm whale, Physeter cation, with special reference to the possible functions of fat depots" (PDF). Journal of the Marine Research Institute. 12 (2). ISSN 0484-9019. Retrieved 2014-04-25. The significant levels of carbohydrate, probably mostly in the form of glycogen, in both blubber and muscle, may represent an instant form of energy for diving via anaerobic glycolysis.
The reason purity matters is that C17 is a byproduct of most MCT oil production processes, and it, along with C6, is a major cause of throat burning and gut irritation. Most MCT’s on the market are manufactured via chemical and solvent based refining, which involves using chemicals like hexane and different enzymes and combustion chemicals, such as sodium methoxide. But ideally, you should get an MCT oil that is made using triple steam distillation in a non-oxygen atmosphere to avoid lipid oxidation and create a purer end-product.
I’ve been experimenting with MCT Oil Brain Octane. I have one questions. I’ve been eating about 20 – 25 gr. of carbs per day on a high fat, medium protein diet. I’m measuring ketones in the morning before taking the MCT and after. I’ve been taking btw. 1-2 tbsp of MCT Brain Octane with butter (Bulletproof coffee) – I measure again after 30 min., 1hr, 2 hrs. and don’t see a raise in my blood ketones. Anything I’m missing, would love to hear your thoughts, Ben. – Thx I’m measuring with Precision Xtra and Ketonix Red.
Variations on the Johns Hopkins protocol are common. The initiation can be performed using outpatient clinics rather than requiring a stay in hospital. Often, no initial fast is used (fasting increases the risk of acidosis, hypoglycaemia, and weight loss). Rather than increasing meal sizes over the three-day initiation, some institutions maintain meal size, but alter the ketogenic ratio from 2:1 to 4:1.[9]
Weight loss is my favorite side effect of keto. Coming in a close 2nd, 3rd, and 4th, and 5th is higher energy levels, no bingeing, clear skin, and lowered blood glucose! I don’t mind telling people that I’m Keto...or shutting down a conversation where they try and spew their online doctor degree about how I’m killing myself. This WOE work is for me, my bloodwork is the best it has ever been, and I feel great. Keto on, friends.
Insulin is a hormone that lets your body use or store sugar as fuel. Ketogenic diets make you burn through this fuel quickly, so you don’t need to store it. This means your body needs -- and makes -- less insulin. Those lower levels may help protect you against some kinds of cancer or even slow the growth of cancer cells. More research is needed on this, though.
A small Feb. 20, 2017, study looked at the impact of a six-week ketogenic diet on physical fitness and body composition in 42 healthy adults. The study, published in the journal Nutrition & Metabolism, found a mildly negative impact on physical performance in terms of endurance capacity, peak power and faster exhaustion. Overall, researchers concluded, “Our findings lead us to assume that a [ketogenic diet] does not impact physical fitness in a clinically relevant manner that would impair activities of daily living and aerobic training.” The “significant” weight loss of about 4.4 pounds, on average, did not affect muscle mass or function.
On a low carb or ketogenic diet my fasting blood sugar is 90-120. I think it may get higher the lower carb I go. Most internet sources say don’t worry about it, worry about your Ha1c. Is this insulin resistance? Anyone have better information? If I do a water fast my morning blood sugar will go down and down each day, til it reaches about 50 in 4 days. But as soon as I start eating it pops right back up.
Easy: use about half of the recommended serving of Glycofuse, and instead add one scoop of Catalyte electrolytes, one scoop of Kion Aminos, and one serving of ketones and/or MCT’s in the form of Brain Octane, KetoCaNa or KETO//OS (pick your poison, it’s up to you). While any of these forms of ketones and/or MCT’s works for daily focus and short workouts, I found that for long workouts they aren’t very gut friendly unless you really spread out the dosage (e.g. one serving every three hours), so you’d only really use that stuff in something like, say, an Ironman triathlon or multi-day adventure race.

"Many of the richest sources of fiber, like beans, fruit, and whole grains are restricted on the ketogenic diet," registered dietician Edwina Clark told Everyday Health. "As a result, ketogenic eaters miss out on the benefits of fiber-rich diet such as regular laxation and microbiome support. The microbiome has been implicated in everything from immune function to mental health."
Ketosis is a metabolic state where most of the body's energy supply comes from ketone bodies in the blood, in contrast to a state of glycolysis where blood glucose provides most of the energy. Ketosis is characterized by serum blood concentrations of ketone bodies over 0.5 millimolar with low and stable levels of insulin and blood glucose. However, with ketone supplementation (as you’ll learn about later in this article) ketosis can actually be induced even when there are high levels of blood glucose.
The reason purity matters is that C17 is a byproduct of most MCT oil production processes, and it, along with C6, is a major cause of throat burning and gut irritation. Most MCT’s on the market are manufactured via chemical and solvent based refining, which involves using chemicals like hexane and different enzymes and combustion chemicals, such as sodium methoxide. But ideally, you should get an MCT oil that is made using triple steam distillation in a non-oxygen atmosphere to avoid lipid oxidation and create a purer end-product.
The ketogenic diet is a high-fat, adequate-protein, low-carbohydrate diet that in medicine is used primarily to treat difficult-to-control (refractory) epilepsy in children. The diet forces the body to burn fats rather than carbohydrates. Normally, the carbohydrates contained in food are converted into glucose, which is then transported around the body and is particularly important in fueling brain function. However, if little carbohydrate remains in the diet, the liver converts fat into fatty acids and ketone bodies. The ketone bodies pass into the brain and replace glucose as an energy source. An elevated level of ketone bodies in the blood, a state known as ketosis, leads to a reduction in the frequency of epileptic seizures.[1] Around half of children and young people with epilepsy who have tried some form of this diet saw the number of seizures drop by at least half, and the effect persists even after discontinuing the diet.[2] Some evidence indicates that adults with epilepsy may benefit from the diet, and that a less strict regimen, such as a modified Atkins diet, is similarly effective.[1] Potential side effects may include constipation, high cholesterol, growth slowing, acidosis, and kidney stones.[3]
Stock up: Jet.com's new City Grocery service (available in select markets) makes it easy to ensure you always have keto-friendly veggies in the fridge. We love their delivery scheduling tool; simply fill your cart, then decide which day and timeframe you'd like your groceries delivered. One of our faves: Urban Roots Green Squash Veggie Noodles are great for whipping up low-carb "pasta" dishes.
Ketosis is a metabolic state where most of the body's energy supply comes from ketone bodies in the blood, in contrast to a state of glycolysis where blood glucose provides most of the energy. Ketosis is characterized by serum blood concentrations of ketone bodies over 0.5 millimolar with low and stable levels of insulin and blood glucose. However, with ketone supplementation (as you’ll learn about later in this article) ketosis can actually be induced even when there are high levels of blood glucose.
Your glycogen stores can still be refilled while on a ketogenic diet. A keto diet is an excellent way to build muscle, but protein intake is crucial here. It’s suggested that if you are looking to gain mass, you should be taking in about 1.0 – 1.2g protein per lean pound of body mass. Putting muscle on may be slower on a ketogenic diet, but that’s because your total body fat is not increasing as much.5Note that in the beginning of a ketogenic diet, both endurance athletes and obese individuals see a physical performance for the first week of transition.

In ketogenesis, two acetyl-CoA molecules instead condense to form acetoacetyl-CoA via thiolase. Acetoacetyl-CoA momentarily combines with another acetyl-CoA via HMG-CoA synthase to form hydroxy-β-methylglutaryl-CoA. Hydroxy-β-methylglutaryl-CoA form the ketone body acetoacetate via HMG-CoA lyase. Acetoacetate can then reversibly convert to another ketone body—D-β-hydroxybutyrate—via D-β-hydroxybutyrate dehydrogenase. Alternatively, acetoacetate can spontaneously degrade to a third ketone body (acetone) and carbon dioxide, although the process generates much greater concentrations of acetoacetate and D-β-hydroxybutyrate. When blood glucose levels are low, ketone bodies can be exported from the liver to supply crucial energy to the brain.[28]


Another possible nutrient deficiency: potassium, a mineral important for both electrolyte balance and blood pressure control, notes MedlinePlus. “Inadequate intake of potassium is likely when consumption of fruits and starchy vegetables are decreased,” says Asche. She recommends adding lower-carb sources of potassium to the diet, including avocado and spinach — as well as lower-carb sources of fiber, such as chia seeds and flaxseed (be sure to enjoy ground for the best health benefits).
I am not a doctor and this is not to be taken, interpreted or construed as medical advice. If you have poor liver or gallbladder function, it can be a good idea to take care of that prior to a high fat diet, yes. But a healthy high fat diet would not cause liver issues per se. These are just my own personal thoughts and not a prescription or a diagnosis or any form of health care whatsoever.
And here’s the reality of the situation. Not all carbs are created equal. There’s a lot of cleverly labeled and modified maltodextrin on the market claiming to be some technical polysaccharide. Or, there’s plain old cornstarch relabeled as super-duper muscle engorging waxy maize. Most of these aren’t proven to do anything except deliver false hopes, high blood sugar, and gut issues – as opposed to having multiple clinical studies in real athletes to support what it is they’re claiming.
Around this time, Bernarr Macfadden, an American exponent of physical culture, popularised the use of fasting to restore health. His disciple, the osteopathic physician Dr. Hugh William Conklin of Battle Creek, Michigan, began to treat his epilepsy patients by recommending fasting. Conklin conjectured that epileptic seizures were caused when a toxin, secreted from the Peyer's patches in the intestines, was discharged into the bloodstream. He recommended a fast lasting 18 to 25 days to allow this toxin to dissipate. Conklin probably treated hundreds of epilepsy patients with his "water diet" and boasted of a 90% cure rate in children, falling to 50% in adults. Later analysis of Conklin's case records showed 20% of his patients achieved freedom from seizures and 50% had some improvement.[10]

“For events longer than 60 minutes, consuming 0.7 g carbohydrates·kg-1 body weight·h-1 (approximately 30-60 g·h-1) has been shown unequivocally to extend endurance performance. Consuming carbohydrates during exercise is even more important in situations when athletes have not carbohydrate-loaded, not consumed pre-exercise meals, or restricted energy intake for weight loss. Carbohydrate intake should begin shortly after the onset of activity; [and continue] at 15- to 20-min intervals throughout the activity.”
A: The amount of weight you lose is entirely dependent on you. Obviously adding exercise to your regimen will speed up your weight loss. Cutting out things that are common “stall” causes is also a good thing. Artificial sweeteners, dairy, wheat products and by-products (wheat gluten, wheat flours, and anything with an identifiable wheat product in it).

Hi Ben – Great article. I had trouble at the end figuring out if you were now eating high fat (60-80% of calories), or if you went back to something closer to 50% fat calories and higher carbs and are using exogenous ketones to get int ketosis when needed. Are you doing any carbs at night or a refeed, or just having higher carbs on most days? Thanks


Have you heard all the buzz about the keto diet and want to know more? Did a friend tell you they’re “in ketosis” and you got interested? Here’s everything you need to know about ketogenic diets and being in ketosis for fat loss, brain function, satiety, and performance. Editor’s Note: This article is being updated … Continue reading The Keto Diet: Next Big Thing or Dangerous Fad?
The ketogenic diet is a medical nutrition therapy that involves participants from various disciplines. Team members include a registered paediatric dietitian who coordinates the diet programme; a paediatric neurologist who is experienced in offering the ketogenic diet; and a registered nurse who is familiar with childhood epilepsy. Additional help may come from a medical social worker who works with the family and a pharmacist who can advise on the carbohydrate content of medicines. Lastly, the parents and other caregivers must be educated in many aspects of the diet for it to be safely implemented.[5]
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