Wondering what fits into a keto diet — and what doesn’t? “It’s so important to know what foods you’ll be eating before you start, and how to incorporate more fats into your diet,” says Kristen Mancinelli, RD, author of The Ketogenic Diet: A Scientifically Proven Approach to Fast, Healthy Weight Loss, who is based in New York City. We asked her for some guidelines.
Alison Moodie is a health reporter based in Los Angeles. She has written for numerous outlets including Newsweek, Agence France-Presse, The Daily Mail and HuffPost. For years she covered sustainable business for The Guardian. She holds a master’s degree from Columbia University’s Graduate School of Journalism, where she majored in TV news. When she's not working she's doting on her two kids and whipping up Bulletproof-inspired dishes in her kitchen.
There are so many tricks, shortcuts, and gimmicks out there on achieving optimal ketosis – I’d suggest you don’t bother with any of that. Optimal ketosis can be accomplished through dietary nutrition alone (aka just eating food). You shouldn’t need a magic pill to do it. Just stay strict, remain vigilant, and be focused on recording what you eat (to make sure your carb and protein intake are correct).
The ketogenic diet is a mainstream dietary therapy that was developed to reproduce the success and remove the limitations of the non-mainstream use of fasting to treat epilepsy.[Note 2] Although popular in the 1920s and '30s, it was largely abandoned in favour of new anticonvulsant drugs.[1] Most individuals with epilepsy can successfully control their seizures with medication. However, 20–30% fail to achieve such control despite trying a number of different drugs.[9] For this group, and for children in particular, the diet has once again found a role in epilepsy management.[1][10]
A ketogenic diet is high in fat and low in carbohydrates. It’s called “ketogenic” because people on this diet shift from using glucose (a type of sugar) as their main fuel source to ketone bodies, which are derived from fat. In other words, people on the ketogenic diet can use their bodies’ fat stores as fuel—and this is why many studies show that this diet is superior for sustainable weight loss.
Cyclical keto diet: The Bulletproof Diet falls into this category. You eat high fat, low carb (less than 50 grams of net carbs a day) five to six days of the week. On day seven, you up your carb intake to roughly 150 grams, during what’s called a carb refeed day. Carb cycling this way helps you avoid the negative effects some people experience when they restrict carbs long term, like thyroid issues, fatigue and dry eyes.[9][10]  Learn more here about how carb cycling works.
As discussed in the first article of this series, ketosis is a metabolic state in which the brain switches to using ketone bodies – derived from the breakdown of fat – as its primary energy source, instead of glucose. This way body protein, which would otherwise be broken down and converted into glucose through the process of gluconeogenesis, are spared.
In terms of weight loss, you may be interested in trying the ketogenic diet because you’ve heard that it can make a big impact right away. And that’s true. “Ketogenic diets will cause you to lose weight within the first week,” says Mattinson. She explains that your body will first use up all of its glycogen stores (the storage form of carbohydrate). With depleted glycogen, you’ll drop water weight. While it can be motivating to see the number on the scale go down (often dramatically), do keep in mind that most of this is water loss initially.
Lurie Children's provides healthcare regardless race, color, religion (creed), sex, gender identity or expression, sexual orientation, national origin (ancestry), or disability. Financial assistance for medically necessary services is based on family income and hospital resources, and is provided to children under age 21 whose primary residence is in Illinois, Indiana, and Wisconsin.
Nina, this is a brilliant article, thank you. I have shared it with my Low Carb & Keto Facebook US & UK groups, many of whom are new to this way of eating for weight loss, reversing Diabetes, preventing Diabetes and improving their health. My members receive regular low carb recipes and support but articles like this, really do reinforce their reasons for staying low carb and helps them justify their lifestyle to family, friends and some Medics!
While many health care providers aren’t comfortable recommending the keto diet for people with diabetes, there’s a substantial body of research indicating that it can help with weight loss, reduce the need for medication, and even lower A1C into the non-diabetes range. It’s so effective that when researchers assigned 349 volunteers with type 2 diabetes to follow either a keto diet or a traditional diabetes eating plan (the makeup of that plan wasn’t defined in the study) for one year, they observed some powerful results. While the people on the “diabetes diet” didn’t experience any positive movement in their A1C, body weight, or medication requirements, those on the keto plan reduced their A1C from 7.6 to 6.3 percent, shed 12 percent of their body weight, eliminated their need for sulfonylurea medication, and lowered or reduced their need for insulin by 94 percent. The results were published in 2018 in the journal Diabetes Therapy.

Lurie Children's provides healthcare regardless race, color, religion (creed), sex, gender identity or expression, sexual orientation, national origin (ancestry), or disability. Financial assistance for medically necessary services is based on family income and hospital resources, and is provided to children under age 21 whose primary residence is in Illinois, Indiana, and Wisconsin.

You’re transitioning. Your body is equipped to process a high intake of carbs and a lower intake of fat. Your body needs to create enzymes to be able to do this. In the transitional period, the brain may run low on energy which can lead to grogginess, nausea, and headaches. If you’re having a large problem with this, you can choose to reduce carb intake gradually.

A ketogenic diet is comprised of approximately 10% of daily calories coming from healthy carbohydrates such as leafy greens, nonstarchy vegetables, and limited amounts of legumes and berries; 20% of daily calories coming from proteins such as omega-3-rich fish and grass-fed animal protein; and ~70% of daily calories coming from high-quality fats such as avocado, unsaturated and medium-chain triglyceride oils, nuts and seeds, and coconut.

Meanwhile, more than 70 trials have examined the health effects of a low-carb diet. They attest to the benefits64 associated with ketosis and low-carb diets, including a reduction in body weight and body mass index, improved cardiovascular risk factors including blood pressure, and the reversal of Type 2 diabetes. It is virtually impossible to imagine that a diet with so many health improvements in the ‘near term’ (2 years) could ultimately shorten life—and the study authors offer no possible mechanism to explain how this might happen.
A ketogenic diet could be an interesting alternative to treat certain conditions, and may accelerate weight loss. But it is hard to follow and it can be heavy on red meat and other fatty, processed, and salty foods that are notoriously unhealthy. We also do not know much about its long-term effects, probably because it’s so hard to stick with that people can’t eat this way for a long time. It is also important to remember that “yo-yo diets” that lead to rapid weight loss fluctuation are associated with increased mortality. Instead of engaging in the next popular diet that would last only a few weeks to months (for most people that includes a ketogenic diet), try to embrace change that is sustainable over the long term. A balanced, unprocessed diet, rich in very colorful fruits and vegetables, lean meats, fish, whole grains, nuts, seeds, olive oil, and lots of water seems to have the best evidence for a long, healthier, vibrant life.
Physicians of ancient Greece treated diseases, including epilepsy, by altering their patients' diet. An early treatise in the Hippocratic Corpus, On the Sacred Disease, covers the disease; it dates from c. 400 BC. Its author argued against the prevailing view that epilepsy was supernatural in origin and cure, and proposed that dietary therapy had a rational and physical basis.[Note 3] In the same collection, the author of Epidemics describes the case of a man whose epilepsy is cured as quickly as it had appeared, through complete abstinence of food and drink.[Note 4] The royal physician Erasistratus declared, "One inclining to epilepsy should be made to fast without mercy and be put on short rations."[Note 5] Galen believed an "attenuating diet"[Note 6] might afford a cure in mild cases and be helpful in others.[11]
The “Dirty Keto” version of high-fat, low-carb dieting promises the same fat-burning results as mainstream keto. The only difference? You can get fat, protein and other macronutrients from any source — including foods like fast-food burgers and sugar-free candy. Dirty keto recipes have gained popularity because they taste great while promoting weight loss. But does dirty keto really work?
Forget the heavy casserole recipes and try this low-carb pot pie tonight! Nothing says comfort food like a chicken pot pie. This low-carb pot pie recipe skips the traditional gluten-filled dough of chicken pot pies and replaces it with cauliflower for a more low-carb option. I simply suggest switching out the cornstarch with arrowroot or tapioca starch.
Even after irradiation (the industry standard sterilization process that also destroys any antioxidants and health benefits), spices and herbs can spoil in your home, and often harbor aggressive mold toxins. To spice up your dishes the Bulletproof way, use high-quality, fresh or recently opened herbs and spices. Spices with especially high mold toxin risk include black pepper, powdered garlic, nutmeg, and paprika. Apple cider vinegar is the only vinegar permitted in the Bulletproof diet, as other vinegars and yeasts introduce toxins, and promote yeast growth in your gut.

The popular low-carb diets (such as Atkins or Paleo) modify a true keto diet. But they come with the same risks if you overdo it on fats and proteins and lay off the carbs. So why do people follow the diets? "They're everywhere, and people hear anecdotally that they work," McManus says. Theories about short-term low-carb diet success include lower appetite because fat burns slower than carbs. "But again, we don't know about the long term," she says. "And eating a restrictive diet, no matter what the plan, is difficult to sustain. Once you resume a normal diet, the weight will likely return."
The modified Atkins diet reduces seizure frequency by more than 50% in 43% of patients who try it and by more than 90% in 27% of patients.[18] Few adverse effects have been reported, though cholesterol is increased and the diet has not been studied long term.[48] Although based on a smaller data set (126 adults and children from 11 studies over five centres), these results from 2009 compare favourably with the traditional ketogenic diet.[18]
Cyclical keto diet: The Bulletproof Diet falls into this category. You eat high fat, low carb (less than 50 grams of net carbs a day) five to six days of the week. On day seven, you up your carb intake to roughly 150 grams, during what’s called a carb refeed day. Carb cycling this way helps you avoid the negative effects some people experience when they restrict carbs long term, like thyroid issues, fatigue and dry eyes.[9][10]  Learn more here about how carb cycling works.
Full disclosure: I have followed a low-carb diet for nearly a decade and find no problem adhering to it. I’ve lost weight and all my cardiovascular biomarkers have improved. Moreover, I’ve studied the science and history behind low-carbohydrate diets, so beyond my personal experience, I bring an evidence-based perspective. (Previously, for 25+ years, I adhered faithfully to a “mostly plants” regimen of fruits, veggies, and whole grains, including my own homemade 7-grain bread, while exercising religiously. Yet during that time my blood lipids were unhealthy, and I never could shake an extra 10-20 pounds.)
The past 4 years I was suffering from mild to severe pain all over my body and unrelenting fatigue, sleep disturbances, brain fog, etc. Diagnosed with Sjogren’s Syndrome and Fibromyalgia. Medication included Vicodin, Morphine and a muscle relaxer. I would not take Plaquenall (spelling?), Lyrica or other “biologics”. I was taking a bunch of supplements but nothing was improving.  
One of the most-cited worries about the keto diet is the long-term impact it may have on heart health—especially because people with diabetes are at greater risk for heart disease. In the small Diabetic Medicine study that found people with type 1 improved their A1Cs on a keto diet, participants had higher triglycerides and LDL (“bad”) cholesterol. This raises concerns about the diet’s longer-term heart health implications, as do the results of research published last year in The Lancet. That study followed more than 15,000 adults for 25 years and found that people who consumed less than 40 percent of their calories from carbohydrates were significantly more likely to die from heart disease than those whose diets contained 50 to 55 percent of calories from carbs—especially if the foods that replaced those carbs were rich in animal fats and proteins.
There are theoretically no restrictions on where the ketogenic diet might be used, and it can cost less than modern anticonvulsants. However, fasting and dietary changes are affected by religious and cultural issues. A culture where food is often prepared by grandparents or hired help means more people must be educated about the diet. When families dine together, sharing the same meal, it can be difficult to separate the child's meal. In many countries, food labelling is not mandatory so calculating the proportions of fat, protein and carbohydrate is difficult. In some countries, it may be hard to find sugar-free forms of medicines and supplements, to purchase an accurate electronic scale, or to afford MCT oils.[54]
Dr. Campos, it is so discouraging to see that you disparage the ketogenic diet based on your assumption that it is very heavy in poor quality processed meats. No diet that relies on processed foods can be viewed as “healthy”. Become better informed by getting up to speed with what Jeff Volek, RD, PhD, calls a “well-formulated ketogenic diet.” Also, learn more about the potential of the diet to slow cancer progression (my specialty). You owe it to your patients who are depending on you for advice. Present them with facts, not opinions.
A slew of articles in recent months have referred to the ketogenic diet as a “fad” or “trend.” It’s “dangerous,” claimed one article, and an anonymous post by the Harvard Public School of Public Health said the diet “comes with serious risks.”1 Yet strangely, these critics seldom cite scientists or doctors who work with the diet, and many—including the Harvard article—cite no medical literature to substantiate their allegations. Without substantiation, many simply rehash long-contradicted, outdated claims.
My point here is that the warnings about the ketogenic principles are well taken and well documented. My concern is implications that this is a fad. I don’t use the word diet with my patients and I’m concerned that the principles behind the label and the real results that these readers have commented on might get minimized. I have found it best to encourage patients to read authors like: Stephen Phinney, Jeff Volek, Patricia Daly, and Charles Gant and the be partners with their doctors and check blood work as they move along. I am not for or against the article. If ketogenic principles offer people enduring, satisfying, and cohesive change then why not read about its potential and flexilbity?

Full disclosure: I have followed a low-carb diet for nearly a decade and find no problem adhering to it. I’ve lost weight and all my cardiovascular biomarkers have improved. Moreover, I’ve studied the science and history behind low-carbohydrate diets, so beyond my personal experience, I bring an evidence-based perspective. (Previously, for 25+ years, I adhered faithfully to a “mostly plants” regimen of fruits, veggies, and whole grains, including my own homemade 7-grain bread, while exercising religiously. Yet during that time my blood lipids were unhealthy, and I never could shake an extra 10-20 pounds.)
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