You’ve probably heard that the ketogenic diet exerts anti-inflammatory effects, turns your body into a fat-burning machine, and allows you to lose weight without counting calories.
And the internet is filled with personal success stories about low-carb, high-fat diets.
But what do the hard scientific data say about keto?
In this article, you’ll learn what peer-reviewed studies and clinical trials have concluded about the ketogenic diet’s potential to prevent disease, enhance health, sustain weight loss, and more.
And equally importantly, you’ll find a discussion of all the areas where the keto diet science is weak or inconclusive: what we don’t know yet.
Keep reading to discover the most important keto statistics and takeaways from the scientific literature.
In a moment, we’ll discuss the best keto stats from cutting-edge research.
But first, to better understand the study findings, let’s take a moment to review the unique mechanisms of the keto diet.
During clinical research, scientists measure the results of an intervention (like the ketogenic diet), but they also investigate any underlying mechanisms or causes.
- Carbohydrate restriction: Because you eat 30 grams or less of carbs per day on keto, the diet can reverse insulin resistance and improve insulin sensitivity, which may help reduce the risk or severity of cardiovascular disease, type 2 diabetes, some cancers, and other chronic diseases[*][*][*][*]. Eliminating toxic sugar is another way that carb restriction augments your health[*][*].
- Increased fat oxidation (fat-burning): As a consequence of cutting back on carbs, your body turns to an alternative fuel source: fat (also called lipids). The reliance on healthy dietary fat intake and stored body fat translates into fewer cravings, higher alertness, and an easier time losing weight[*][*].
- Ketone production: When you restrict carbohydrate intake and switch into fat-burning mode, your liver creates ketones during the breakdown of fat in a process called ketosis[*]. Ketones like beta-hydroxybutyrate are a high-energy, clean-burning brain fuel shown to increase mental clarity and decrease inflammation, especially in the central nervous system[*][*][*][*].
As you learn about the research-backed health benefits of keto, keep in mind that virtually all of them come from eating fewer carbs, increasing fat-burning, and the natural production of ketones in your body.
Alzheimer’s disease is a form of progressive dementia. Individuals with Alzheimer’s disease experience greater confusion and disorientation over time, eventually becoming completely dependent on caretakers.
Scientists and doctors have observed that Alzheimer’s patients have reduced brain blood flow, difficulty using sugar as brain fuel, insufficient energy for brain function, and damaged brain cells from free radicals[*][*][*][*].
Here’s what we know (and don’t know) about Alzheimer’s disease and the keto diet:
- Insulin resistance is a risk factor for Alzheimer’s dementia, and the keto diet helps reverse insulin resistance[*][*][*][*]. Therefore, keto may reduce the risk of Alzheimer’s by decreasing insulin resistance.
- The anti-inflammatory mechanisms of the ketogenic diet may directly reduce Alzheimer’s risk[*].
- Ketones from going keto or taking keto supplements can act as an alternative fuel for the brains of people with Alzheimer’s[*][*].
Here’s what the data says about Alzheimer’s and keto:
- A 2004 study found that ketogenic MCT oil supplements helped improve cognition and memory for some patients with impaired mental function caused by Alzheimer’s[*].
- A 2019 case study of a 71-year-old woman with mild Alzheimer’s and insulin resistance found that after 10 weeks of the keto diet, her insulin resistance decreased by 75%, triglycerides decreased 50%, VLDL cholesterol dropped 50%, and cognitive measures improved by 33%[*].
- A 2017 trial found that in 10 patients with mild-to-moderate Alzheimer’s, the keto diet supplemented with MCT oil resulted in nutritional ketosis and improved cognitive scores[*]. However, 5 other patients with moderate or severe Alzheimer’s were unable to complete the trial due to difficulty following the diet.
- A separate 2019 trial in Alzheimer’s patients found that keto was feasible and sustainable for two-thirds of participants[*]. The participants could eat enough calories and essential nutrients while maintaining a state of ketosis.
And here are the key takeaways from the research:
- Some researchers, including the authors of a 2019 paper, believe that if begun early enough, the keto diet may be effective for preventing Alzheimer’s disease[*].
- A 2020 review of 22 studies (11 human and 11 animal studies) found that the keto diet or keto supplements are effective for enhancing cognition in Alzheimer’s patients, especially when taken earlier in the course of the disease[*].
- Patients with more advanced Alzheimer’s disease may benefit more from taking ketogenic supplements like BHB and MCT oil, which might be easier than adopting an entirely new diet.
Extensive research that’s underway now will shed more light on keto and Alzheimer’s in the near future.
But the existing evidence is extremely positive. It looks as though keto can dramatically reduce the risk of Alzheimer’s, or for Alzheimer’s patients, safely decrease symptom severity.
Parkinson’s disease is a long-term degenerative disorder of the nervous system that primarily affects motor function. Symptoms include slowing of movements, tremors, and rigidity[*].
Researchers aren’t entirely sure of the causes of Parkinson’s, but they know it involves the loss of neurons that produce dopamine, which leads to problems with movement[*].
Compared to Alzheimer’s, there’s less research into the effects of keto on Parkinson’s at this point.
Here’s what we know so far:
- A 2009 animal study found that when given a keto diet, ketone production helped to protect rats against the loss of dopaminergic neurons by increasing natural antioxidant levels[*].
- A 2005 study of 7 volunteers with Parkinson’s found that 5 of the participants were able to complete a 28-day ketogenic diet, all of whom experienced improvements in Parkinson’s disease symptoms[*]. However, due to a lack of a control group, the researchers could not rule out a placebo effect.
- A 2018 trial comparing the effects of a low-fat diet versus the keto diet in Parkinson’s patients found that while both diet groups experienced improvements in motor symptoms, the keto diet group also had noteworthy improvements in pain, fatigue, daytime sleepiness, and cognition[*].
So far, the early evidence is hopeful, but no large controlled trials have investigated the use of keto for Parkinson’s.
Additionally, some scientists think that appetite reduction often associated with going keto, which is beneficial for weight loss, could be a problem for frail or elderly Parkinson’s patients[*].
Anyone with Parkinson’s who is considering going keto should consult with a doctor, dietitian, or nutritionist to be sure they get enough calories.
Unlike Alzheimer’s and Parkinson’s, MS typically initially affects people between the ages of 20-40[*].
Here are the stats from studies on keto and MS:
- A preliminary study of 20 individuals with multiple sclerosis published in 2019 found that a keto diet was safe and decreased body mass, body fat, fatigue, and depression in MS patients[*].
- A 2012 study found that in mice, the keto diet helped improve motor function, learning, and memory as well as reverse brain damage and autoimmune effects associated with an experimental version of multiple sclerosis. Additionally, the keto diet decreased free radicals and lowered inflammation levels, resulting in a neuroprotective effect[*].
- A 2019 pilot study of 27 MS patients found that going keto increased lean muscle mass and reduced inflammation and cellular stress[*].
- A randomized controlled trial of 60 adults with multiple sclerosis published in 2018 concluded that the keto diet decreased levels of inflammatory signaling chemicals, which may improve the effectiveness of MS therapies[*].
- A 2017 trial found that while many MS patients have gut bacteria problems, the ketogenic diet may help restore healthy microbiome diversity[*].
The evidence that keto can help MS patients is growing all the time. Currently, the prospect that the ketogenic diet could slow the course of multiple sclerosis appears favorable.
For much of the 20th century, the mainstream medical paradigm held that saturated fat clogged arteries, resulting in heart disease and poor cardiovascular health[*].
Keeping in mind that fat is no longer the “bad guy” of the nutritional world, here’s what the peer-reviewed literature tells us about low-carb, high-fat diets and cardiovascular health and safety:
- A 2020 meta-analysis of 12 separate studies found low-carb diets significantly lowered triglycerides, reduced body weight, decreased blood pressure, lessened total cholesterol, and raised HDL cholesterol[*].
- According to the authors of a 20-year study of over 80,000 women published in the New England Journal of Medicine in 2006, “findings suggest that diets lower in carbohydrate and higher in protein and fat are not associated with increased risk of coronary heart disease in women”[*].
- A study of 83 obese patients published in 2004 examined the cardiovascular effects of a 6-month keto diet with 30 grams of carbs per day. It found that along with significant reductions in body weight and body mass, going keto reduced the subjects’ triglycerides, LDL (“bad”) cholesterol, and blood glucose, as well as increased HDL (“good”) cholesterol–all without any unwanted side effects[*].
- In 2002, a 6-week study of 20 men with healthy body weight and normal cholesterol levels found that going keto significantly decreased triglycerides, improved fat metabolism, lowered fasting insulin levels, increased HDL cholesterol, and shifted the LDL cholesterol particle pattern to a healthier (larger) type of cholesterol particle[*].
- A 2015 year-long study of 377 obese patients found that the keto diet safely led to weight loss, lower blood pressure and other improvements in cardiovascular risk factors[*].
At this point, the evidence clearly shows that going keto is not only safe for your heart but is also an excellent decision for cardiovascular health.
Type 2 diabetes occurs when severe insulin resistance leads to high blood sugar levels, which are potentially damaging to your body[*]. Some people with type 2 diabetes are also insulin-dependent, meaning they must inject insulin to control blood glucose.
In contrast, type 1 diabetes, also called autoimmune diabetes, usually occurs in childhood and does not appear to be a result of diet or other lifestyle factors. Type 1 diabetes typically involves reduced insulin production by the pancreas, but may not include insulin resistance[*].
As discussed earlier in this article, one of the primary mechanisms behind the benefits of keto is lowering insulin resistance. Here’s how that translates in terms of keto and diabetes research statistics:
- A 2019 paper published in Current Nutrition Reports concluded that the keto diet can reduce the risk or severity of type 2 diabetes by improving factors like obesity, fasting blood sugar, high triglycerides, low HDL cholesterol, and hypertension[*].
- In a 2016 review, the Obesity Medicine Association stated that “research demonstrates that the lowering of insulin levels [on the ketogenic diet] dramatically improves diabetes and the factors associated with metabolic syndrome including central obesity, high blood pressure, and elevated blood lipids, which, of course, are risk factors associated with [other severe medical conditions]”[*].
- A 2012 study of 363 overweight and obese people, some of whom had type 2 diabetes, compared the keto diet to a conventional low-calorie diet. It found that keto led to more significant improvements in body mass index, waist circumference, blood glucose, hbA1c, cholesterol, triglycerides, uric acid, and other health markers[*]. Additionally, many participants in the keto group were able to decrease their diabetes medication by half or more or discontinue medication usage altogether.
- A 2019 review in the journal Nutrients found that for people with type 1 diabetes, keto seems to provide mixed results: it appears to make blood glucose management easier and improve insulin sensitivity, but may also increase the risk of low blood sugar[*].
According to the best available evidence, the keto diet appears to be highly effective for managing type 2 diabetes and its symptoms.
There’s less evidence to support the use of keto for type 1 diabetes, but the existing evidence is still promising. Although keto is unlikely to eliminate the dependence on insulin injections, it may help simplify blood glucose management.
However, because it could dramatically decrease your medication requirements, make sure to speak to your doctor if you’re considering keto for diabetes[*].
As we’ve established in previous sections, evidence shows that the keto diet can decrease many risk factors for cancer, including excess body fat, insulin resistance, high blood sugar, and cellular stress[*].
Here’s what the best studies tell us about keto and preventing or treating cancer:
- Much of the current human evidence for the keto diet in cancer treatment is in brain tumors, where researchers have noted increased survival times as well as the safety of the diet[*].
- The authors of a 2020 paper noted that early evidence supports the use of keto as a complementary or alternative therapy for some types of breast cancer[*].
- According to the authors of a 2018 peer-reviewed paper, “the rationale in providing a fat-rich, low-carbohydrate diet in cancer therapy is to reduce circulating glucose levels and induce ketosis such that cancer cells are starved of energy while normal cells adapt their metabolism to use ketone bodies and survive. Furthermore, by reducing blood glucose also levels of insulin and insulin-like growth factor, which are important drivers of cancer cell proliferation, drop”[*].
- A 2017 review of the ketogenic diet as a cancer treatment in animal models found that of 13 total studies, 9 indicated a beneficial effect of the keto diet on tumor growth and survival time. Tumor types included pancreatic, prostate, gastric, colon, brain, neuroblastoma, and lung cancers[*]
- Thanks to a process called autophagy (“self-eating”) that occurs during ketosis, the keto diet is effective at clearing out old defective cells, which may reduce tumor risk in people who don’t have cancer[*].
Currently, the strongest evidence exists in support of keto for cancer prevention. Improving cancer risk factors by going keto is a wise strategy for people who seek to stay cancer-free.
And while some scientific evidence supports the use of the ketogenic diet as a complementary cancer therapy, there’s no one-size-fits-all approach to treating cancer.
If you’re considering incorporating the ketogenic diet as a complementary or alternative cancer therapy, make sure to consult an oncologist first to determine whether it’s a good fit.
The effects of keto on muscle mass can vary greatly depending on the individual.
A 2017 study of 20 obese individuals found that despite inducing weight loss and fat loss, the keto diet preserved lean muscle mass and strength levels[*].
And other studies have found that compared to low-fat diets, very-low-carb diets like keto likely spare muscle mass during weight loss[*].
On the other hand, a 2018 randomized controlled trial found that compared to a non-keto diet, the keto diet resulted in fat loss but did not increase muscle mass despite the inclusion of a calorie surplus and weight training program[*].
A similar 2020 study of 21 women found that when paired with resistance exercise, the keto diet resulted in fat loss without lean muscle gain[*].
In contrast to the other findings, an 11-week study published in 2017 noted that resistance-trained men who went keto gained lean mass, while men who followed a “Western diet” did not[*].
The main difference between the standard keto diet and other diets people use to gain muscle mass is the lack of carbohydrates.
If you’re struggling to add muscle on keto, a keto-based approach that allows more carbs, such as targeted keto or cyclical keto, may work better.
Here are the stats on pure strength and the keto diet:
- A 2018 study of recreational CrossFit athletes found that going keto for 3 months reduced body fat, but did not negatively impact 1-rep-max back squat[*].
- In a separate 2018 crossover study of intermediate to elite powerlifting and Olympic weightlifting athletes, researchers found that the keto diet led to weight loss[*]. However, strength performance did not differ on keto compared to the athletes’ usual diet.
- According to results published in 2017, an 11-week study found no difference in strength or power in resistance-trained men who worked out following the keto diet versus a conventional diet that included carbs[*]. Both groups got stronger and increased their power.
There should be no problem whatsoever with going keto if your main concern is gaining or preserving strength.
Some scientists consider the keto diet promising for physical performance, especially for endurance athletes[*].
Because going keto increases your ability to burn fat for fuel, the logic is that it could also enhance endurance performance[*].
But if you’re going to try cutting carbs to enhance performance, it may take some time. If you rush in without a plan, going keto could temporarily reduce performance[*].
Here’s what we know from studies on keto and athletic performance:
- A 2020 study of elite racewalkers found that going keto slowed the athletes down by around 2.3% during competition despite increasing fat-burning[*].
- A 2017 study of 5 endurance athletes noted improvements in body composition, fat burning, skin appearance, and exercise recovery, but also found performance suffered, especially at high exercise intensities[*].
- A 2018 study of 20 endurance athletes found that compared to maintaining a high-carb diet, switching to keto for 12 weeks increased 6-second sprint peak power and improved performance in the critical power test (CPT) by 1.4 watts per kilogram[*]. In contrast, both fitness measures decreased in the high-carb group.
- A 2019 study of soldiers in the US military comparing keto versus a conventional diet found that the keto group had similar performance results to non-keto (and also lost fat without counting calories)[*].
Lastly, some scientists and coaches suggest that training in a state of ketosis, then refueling with carbs prior to competition, could offer the best of both worlds[*].
Weight loss and fat-burning benefits may be why keto is one of the most popular diets today, and for good reason.
There’s no shortage of research backing up the keto diet’s ability to produce weight loss with minimal effort. Here are some of the most impressive statistics on keto and weight loss:
- A 2013 meta-analysis including 13 studies and 1415 participants concluded that compared to a low-fat diet, the keto diet resulted in more long-term weight loss as well as greater improvements in health measures[*].
- Numerous studies prove that the ketogenic diet leads to reductions in appetite, allowing people to lose weight without counting calories or feeling hungry[*][*][*][*].
- During low-intensity exercise in the “fat-burning zone,” keto-adapted individuals can burn over 1.5 grams of fat per minute[*]. There’s literally no other way to safely burn that much fat.
A 2020 paper published in the Journal of Nutrition sums it up best: “Based on available evidence, a well-formulated ketogenic diet does not appear to have major safety concerns for the general public and can be considered a first-line approach for obesity”[*].
More studies than ever before point to the safety and efficacy of the ketogenic diet.
Whether you want to lose weight, prevent disease, or reduce the severity of symptoms, going keto can move you closer to your goals.
But remember the bottom line: reading all the studies in the world and increasing your knowledge doesn’t make you healthier unless you take action.
And if you’re considering keto for Parkinson’s, diabetes, or cancer, please consult your doctor to ensure you’re taking the safest possible approach.