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Ketogenic diet

Keto was the most-Googled diet of 2018. It limits carb intake to under ~50 grams a day, and typically reduces appetite and intake of easy-to-overeat, hyperpalatable foods. However, most trials don't show a large weight loss advantage over higher carb diets, although individual results vary widely. Keto has therapeutic potential for a variety of health conditions. Stay tuned to this page, as 140+ trials are ongoing!

Our evidence-based analysis on ketogenic diet features 105 unique references to scientific papers.

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Summary of Ketogenic diet

Primary information, health benefits, side effects, usage, and other important details

What is keto, and how is it different from "low carb"?

Keto is a fairly simple concept to understand:

Research studies generally peg under 50 grams as ketogenic, and 50-150 as "low-carbohydrate".[1][2] When most people eat less than around 50 grams a day of carbohydrate, they soon start producing high levels of something called "ketone bodies". These are simply breakdown products of fat, and are used to fuel cells that normally depend on glucose.

Why might keto help improve your health?

Keto's impact on health isn't so simple.

Your brain and nervous system usually run on glucose. Fueling it mostly with ketones is a whole new world to these cells, and may provide benefit. The main condition this has been studied for is epilepsy, but more research on other conditions is underway.

Keto's impact OUTSIDE of that, though, is more complicated. Keto is purported to aid with weight loss more so than other weight loss diets. The evidence for this is mixed, but tends to show fairly similar weight loss as other diets, according a meta-analysis of 32 trials comparing carb levels.[3] Keto benefits for a variety of conditions may stem from restriction of carbohydrate,[4] avoidance of typical carb-containing processed junk foods (so not the carb itself, but the food that contains it),[5][6] and/or benefits from the ketone bodies themselves.[7][8][9]

Is keto safe? Are there any detriments?

There are three different purported reasons that keto might not be totally safe:

First is the claim that high levels of ketones can be dangerous. This is generally not true with ketogenic diets, as ketoacidosis (dangerously high ketone levels typically caused by diabetes) doesn't seem to occur absent an uncontrolled medical condition, with no cases being reported in a two-year ketogenic diet study.[10] However, possibly the first case of ketoacidosis in a nondiabetic patient was reported in 2015, in a lactating woman on a ketogenic diet.[11]. A later case study purported to be the first of a healthy, nondiabetic, and non-lactating woman experiencing ketoacidosis.[12] 

Ketone bodies are acidic by their very nature, although blood pH is typically well-regulated by our kidneys and lungs. While there may be a theoretical detriment to mild acidosis,[13] trials haven't shown adverse effects of sustained production of ketone bodies over time.

Second is the idea that going too long without getting "enough" carbohydrate is inherently dangerous. This is also generally not true, as carbohydrate isn't an essential nutrient (you can make all you need to survive, by a process called gluconeogenesis, without ingesting any through food or drink).[14] There isn't any trial evidence though on what the long term effects (e.g. 5-10 or more years) of carbohydrate deprivation are, and whether ketogenic diets have any negative impact on unstudied health conditions, certain genotypes, etc.

Finally, there are claims of harm from diets high in animal products, and most keto diets happen to be high in animal products. This claim is nearly impossible to evaluate with a simple yay or nay, given the huge number of studies involved with varying conclusions. What we know is that evidence is mixed, and slightly differs depending on the animal product in question (for example, fish consumption often shows a slight benefit for longevity in observational studies)[15][16]. Multi-decade randomized trials aren't feasible for foods, so we have to rely on imperfect evidence. In prospective (non-trial) studies, processed red meat often has a strong correlation with increased all-cause mortality and diseases, whereas unprocessed red meat often has a much smaller or no correlation.[17][18][19] Egg consumption typically shows negligible or no detriment to all-cause mortality and disease, [20][21] although again, evidence is mixed, with some other reviews finding a correlation of high egg intakes to disease.[22] 

Meta-analytic results can differ depending on timeframe (intermediate versus longer term outcomes), which studies are excluded and included, and a variety of other factors. Some studies are funded by financially-interested parties (for example, the beef and egg industries), raising the possibility of publication bias or other biases. But other non-industry funded studies also tend to back up a detriment primarily from processed meats, and less or negligible detriment from unprocessed meats, depending on the amount eaten. This will remain an open question, given the difficulty in conducting long term randomized diet trials.

Looking for a no-hype guide to the ketogenic diet?

Wether you're already on keto or thinking about it, our Evidence-based Keto guide will help answer all your questions.

From keto's effects on exercise, fat, muscle, disease, and more to potential long-term health issues that are overlooked, we take a science-based approach to help you get the most out of keto.

It's simply light-years ahead of any other keto guide.

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How to Take

Medical Disclaimer

Recommended dosage, active amounts, other details

Consume under 50 grams of carbs a day, generally. Some people may need to lower this to under 20 grams, and some can produce more ketones even above 50 grams.

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Human Effect Matrix

Unlocked for Examine members

The Human Effect Matrix summarizes human studies to tell you what effects Ketogenic diet has on your body, how much evidence there is, and how strong these effects are.

Full details are available to Examine members.
Grade Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Level of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
Outcome Magnitude of effect
? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
Notes
grade-b Strong High See all 19 studies
A pronounced and persistent decrease in circulating triglycerides is seen the majority of keto diet trials. Importantly, this drop is seen in what long-term trials are available.
grade-b Notable Moderate See all 22 studies
In both short and long-term trials, a keto diet has been shown to notably reduce fasting blood glucose independently of weight loss when compared with various other control diets (usually low-fat diets). Particularly in those with elevated levels to begin with. Glycemic variability may be reduced,, and average glucose levels throughout the day will tend to be lower. Ketogenic diets tend to worsen carbohydrate tolerance during postprandial testing.
grade-b Notable High See all 21 studies
While not necessarily more potent than all control diets, studies have generally found a notably larger reduction in fasting insulin, independently of weight loss. The average insulin levels throughout the day tend to be lower on a ketogenic diet as well.
grade-b Notable Very High See all 17 studies
There appears to be a reliable and significant increase in circulating LDL cholesterol when people undertake a keto diet. In what long-term trials we have, this effect appears to persist on average.
grade-b Notable Very High See all 16 studies
Due to the increase in LDL, total cholesterol tends to be notably higher on a ketogenic diet than diets lower in fat, Even when ketogenic diets lead to more weight loss, total cholesterol and LDL still tend to be higher on ketogenic diets. Some of this effect is likely to be due to lower fiber intake, but some is inherent to diets high in palmitic acid.
grade-b Minor High See all 17 studies
Most trials, across various health condition, have seen a keto diet modestly increase HDL-C levels. This can be due, in part, to an increase in overall fat intake.
grade-b Minor Moderate See all 15 studies
In studies where calories are matched, there isn't generally a difference between ketogenic diets and control diets, and what differences there are can generally be attributed to a loss in water. Ketogenic diets often lead to spontaneous weight reduction even when the aim isn't to reduce calories.
grade-c Strong Very High See all 5 studies
The greater reliance on fatty acids for energy leads to an increase in circulating free fatty acids.
grade-c Strong Very High See all 8 studies
When a ketogenic diet is followed, ketone bodies will increase considerably. Ketosis is compatible with a wide range of protein intakes as long as carbohydrate intake is low, but the most ketogenic diets will be the ones low in both carbohydrates and protein.
grade-c Notable Moderate See all 9 studies
Studies have generally found notably higher c-reactive protein on a ketogenic diet than control diet. Some studies have found no difference and some have found a greater reduction, one with considerably greater weight loss in the ketogenic group, and the other with unbalanced baseline levels.
grade-c Notable High See all 10 studies
Calculations based on glucose and insulin such as HOMA and QUICKI suggest an improvement in insulin sensitivity on ketogenic diets, even independently of weight loss. One study used a euglycemia hyperinsulinemia clamp and found an improvement in insulin sensitivity, but it was confounded by weight loss.
grade-c Minor Moderate See all 4 studies
Flow-mediated dilation is sometimes worsened on a ketogenic diet and improved on a low-fat diet, although this isn't always the case in studies.
grade-c Minor Moderate See all 11 studies
The effects of a ketogenic diet are likely reducible to its effects on calorie intake. Strictly controlled calorie intake means no difference, and ad libitum diets often mean greater fat loss, but sometimes don't.
grade-c Minor Moderate See all 10 studies
Studies generally find no difference or a decrease in the ketogenic group. The decrease may have to do with either greater calorie restriction, more water loss, or increase utilization of amino acids for glucose.
grade-c - Moderate See all 9 studies
Studies that find a greater reduction in blood pressure compared with the control group are studies where the ketogenic diet group experience greater weight loss. When calories are matched, there is generally no difference.
grade-d Notable Very High See all 5 studies
Notable, consistent reduction in the studies.
grade-d Notable - See study
One study found a notable increase. The reason is unknown though increased absorption from increased protein intake can be ruled out.
grade-d Notable Very High See 2 studies
Two studies have found an increase, which makes sense given the greater liberation of fatty acids from triglycerides for energy.
grade-d Notable - See study
One study found a greater reduction in fibrosis after 1 and 2 years of a ketogenic diet that led to substantial weight loss than a control diet that didn't.
grade-d Notable - See study
The ketogenic diet group didn't see much of a difference but the low-fat control group saw a notable reduction.
grade-d Minor Moderate See all 4 studies
Studies have found notable increases in studies where calories are matched and when they're's more weight loss in the ketogenic group. On the other hand, another calorically matched study found a reduction. One found no real effect despite weight loss.
grade-d Minor - See study
One study found somewhat lower levels than on a medium or high carbohydrate diet.
grade-d Minor Very High See all 3 studies
Studies so far have found small to notable increases in cortisol.
grade-d Minor Moderate See all 6 studies
While inconsistent, some studies have found an increase in the ketogenic group. It's possible that some of the effect may be due to increased meat consumption, in a similar way that supplementation creatine increases levels, though more research is needed.
grade-d Minor - See study
Reduction in one study. Needs replication.
grade-d Minor - See study
Somewhat of an increase in one study with ad libitum energy intake.
grade-d Minor Very High See all 5 studies
Small increases in most studies, independently of caloric intake. The one study that found a reduce compared with the control group was a very low calorie diet for both groups.
grade-d Minor - See study
Somewhat of an increase in one study compared with a calorically matched control.
grade-d Minor High See all 4 studies
Most studies have found a reduction, and the one that didn't was far too short to evaluate the effect of a ketogenic diet. More research is needed in type 2 diabetics.
grade-d Minor - See study
One study found a greater increase than the control group, likely due to reduced folate intake.
grade-d Minor - See study
One study found a small reduction. The implication isn't dehydration, but less water needed for glycogen storage.
grade-d Minor - See study
One study found a small increase compared with the control group.
grade-d Minor Very High See 2 studies
Somewhat of a reduction in two trials where the ketogenic group reduced calories and lost weight.
grade-d Minor - See study
One study found an increase and one found a decrease, but neither were too dissimilar to that of the control group.
grade-d Minor - See study
One study found a great reduction in ALT, AST, and ALP after 1 and 2 years on a ketogenic diet that led to substantial weight loss than on a control group that didn't.
grade-d Minor High See all 3 studies
Mixed results, and the study that found the large reduction observed considerably more weight loss in the ketogenic group. More research is needed.
grade-d Minor - See study
A small reduction in one uncontrolled study where caloric intake was reduced on the ketogenic diet.
grade-d Minor - See study
Somewhat lower than while on a medium or high carbohydrate diet.
grade-d Minor Moderate See 2 studies
There was a similar reduction to a control group in one study without much of a difference in weight change, and a more notable reduction in an uncontrolled study where the participants lost a modest amount of weight.
grade-d Minor High See all 3 studies
In one study, T4 declined less in the ketogenic group than a control group, there was no difference after 2 years in another study where the ketogenic group lost considerably more weight, and there was a small increase in one uncontrolled 6-week study.
grade-d
Minor
- See study
In one study, nonmotor and motor daily living experienced improved more in a ketogenic group, while the other group improved more in the motor examination and motor complications. More research is needed.
grade-d Minor Very High See all 4 studies
The increase is consistent across all studies
grade-d Minor Very High See 2 studies
Either a decrease in an uncontrolled trial or less of an increase compared with a control group in another.
grade-d Minor - See study
Somewhat of a decrease after 1 and 2 years, with a greater decrease after to. The control group so no real change.
grade-d Minor High See all 3 studies
Decreased more than in the control group in 2 studies, and in one study there was no difference. It's unclear why studies differed.
grade-d - Very High See 2 studies
No apparent effect in 2 studies where the ketogenic group lost more weight.
grade-d - - See study
No apparent difference in augmentation index in one study that lasted 8 weeks.
grade-d - - See study
No apparent difference between diets in one study.
grade-d - - See study
Unclear effevts from one study. More research is needed.
grade-d - Moderate See 2 studies
Unclear effects from 2 studies. One found a reduction but wasn't controlled.
grade-d - - See study
No change in spine BMD after 2 years and considerable weight loss.
grade-d - Moderate See 2 studies
Inconsistent effects from 2 studies.
grade-d - - See study
No apparent effect in one study.
grade-d - Moderate See 2 studies
Inconsistent effects in 2 studies.
grade-d - - See study
No apparent effect in one study.
grade-d - - See study
No apparent effect in a short-term, uncontrolled study.
grade-d - See study
No apparent effect in one 6-week study.
grade-d - Moderate See 2 studies
The results of two don't suggest a noticeable influence.
grade-d - - See study
No apparent effect in one study.
grade-d - - See study
No apparent effect in one study.
grade-d - Very High See 2 studies
One study found an initial increase followed by a return to roughly baseline, while the other found no notable difference in the increase compared with the control diet.
grade-d - - See all 3 studies
Inconsistent results but compatible with the effect being secondary to body fat reduction.
grade-d - - See study
No apparent effect in one study.
grade-d - Moderate See all 5 studies
No notable difference between groups when calories are matched, and a reduction in two uncontrolled trials with weight loss, as could be expected.
grade-d - - See study
No apparent effect in one short study.
grade-d - - See study
No apparent effect in one short study.
grade-d - Moderate See 2 studies
No apparent effect in one study and a greater reduction than the control group in another study. More research is needed.
grade-d - - See study
No apparent effect.
grade-d - - See study
No apparent effect.
grade-d - - See study
No apparent effect.
grade-d - - See study
No apparent effect in one study.
grade-d - - See study
No apparent effect in one study.
grade-d - - See 2 studies
There was a small decrease in one study with substantial weight loss and a slight increase in one study with slight weight loss.
grade-d - Moderate See all 5 studies
There's unlikely to be a notable change on a ketogenic diet, though uric acid declined considerably more on a control diet in one study.
grade-d - - See study
Absolute VO2 peak declined slightly and relative VO2 peak was unchanged in one uncontrolled study of 6 weeks on a ketogenic diet.
grade-d - - See study
No apparent effect in one study.
grade-d - Moderate See 2 studies
There was a decrease compared to a control group in one 6-week study, and no difference in activity in another study that lasted for 1 week.

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Frequently Asked Questions and Articles on Ketogenic diet

Low-carbing for endurance: the oxygen problem
You might have seen more low-carb endurance athletes popping up in the past few years. This trial tested a ketogenic diet in world-class athletes, compared to two different carb regimens.
Five reasons why you need Evidence-based Keto
If you want to derive maximum benefit from your keto diet, you need to know about the latest evidence. Evidence-based Keto analyzes those studies as objectively as possible, in a way that’s neither pro-keto or anti-keto, covering benefits, long-term safety, and all the dozens of questions we get asked about.

Things to Note

Also Known As

TKD, CKD, VLCKD, LCKD, keto

Do Not Confuse With

Atkins, Low-carb

If you're trying keto for the first time, and haven't previously done a low-carb diet, you'll be more likely to experience the "low-carb flu" (which isn't actually a communicable disease!). It may be wise in these cases to ratchet down your carb intake over time. Make sure you ingest enough electrolytes and calories in the first few days.

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Click here to see all 105 references.