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.
^ Freeman JM, Vining EP, Pillas DJ, Pyzik PL, Casey JC, Kelly LM. The efficacy of the ketogenic diet—1998: a prospective evaluation of intervention in 150 children. Pediatrics. 1998 Dec;102(6):1358–63. doi:10.1542/peds.102.6.1358. PMID 9832569. https://web.archive.org/web/20040629224858/http://www.hopkinsmedicine.org/press/1998/DECEMBER/981207.HTM Lay summary]—JHMI Office of Communications and Public Affairs. Updated 7 December 1998. Cited 6 March 2008.
For many people, one of the more surprising side effects of starting a ketogenic diet is a bout with the “keto flu.” How so? “When you go on this diet, your kidneys don’t retain as much salt or water, which can lead to flu-like symptoms, such as fatigue and headache, or constipation,” says Laura Saslow, PhD, an assistant professor at the University of Michigan School of Nursing. “But these are typically short-lived symptoms that can be prevented or treated by increasing your salt and water intake.” However, if you have high blood pressure, speak with your doctor before adding more sodium to your diet. And know that the keto flu only lasts a week or two; symptoms typically subside once the body adjusts to the diet.

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]


I tried the keto diet a couple years ago and about 6 weeks in of following it closely I started having significant episodes of lightheadedness and anxiety like symptoms. The coach I was working with said it was keto flu so I continued on the diet for a couple more weeks but it was making life difficult so I stopped. Now every time I try to go low carb the symptoms come back. Sometimes I wonder if it’s just anxiety response or all in my head. I would love to eat low carb but haven’t ever been able to figure out why this happens. I read somewhere that keto can be harder for women’s bodies and affect their adrenal glands. Would this increase anxiety symptoms.
“However, saturated fat has long been lauded as a heart-harming macronutrient; the American Heart Association recommends no more than 13 grams of saturated fat per day. In fact, Nieca Goldberg, M.D., medical director of the Joan H. Tisch Center For Women’s Health at NYU Langone Medical Center, said saturated fats can increase bad cholesterol.” -Christina Stiehl, PopSugar reporter17
The keto diet changes the way your body converts food into energy. Eating a lot of fat and very few carbs puts you in ketosis, a metabolic state where your body burns fat instead of carbs for fuel. When your body is unable to get glucose from carbs, your liver converts fatty acids from your diet into ketones, an alternative source of energy. Burning ketones in place of glucose reduces inflammation and spurs weight loss.[1]

Thanks for this article. I just started a Keto diet so found it appropriate to my current lifestyle. Though I don’t believe your bottom line is strong enough since you simply stating that the diet is “hard to follow” and food is “notoriously unhealthy” without evidence going deeper into why those “notoriously unhealthy” foods are worse than keeping carbohydrate-heavy food that are addictive and give the body a quick sugar high for energy. I believe “hard to follow” is your opinion only, since acceptable Keto foods are found at all restaurants easily and also all grocery stores. All the foods you mention: “rich in very colorful fruits and vegetables, lean meats, fish, whole grains, nuts, seeds, olive oil, and lots of water” are all Keto-friendly. Many people have been on a Keto-diet for years. A healthy lifestyle is a healthy mindset change and making right choices – it’s not going to be easy.
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.
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.
I have been on a low carb keto diet for more than a year. As T2DM my A1C dropped from 9% to 5.4% & I discontinued meds. All my lipids improved even with ample healthy saturated fat. More than a year now so I wonder why this would be a short term improvement when its obvious that I will not go back to a high A1C and taking 3 diabetes medications including sulphonylureas. It is clear from this article that you lack the necessary experience that would be gained from wholeheartedly trying the diet or monitoring patients doing it properly like me. I would be probably be facing my first amputation if I believed the negativity in your article. So for people with diabetes who may be dissuaded by your article. Ignore it and take back your health by restricting carbs (<25 g a day) or as low as you reasonably can below 130g while being satisfied that you are getting adequate nutrition.
I was a Corpsman (not a corpse-man as some recent somewhat fanatical president would say), and I can tell you many stories of Marines and Sailors who maintained restrictive diets (aka picky eaters). Most obvious was lack of sustaining energy (hypoglycemia) at mile 15 (with 80lbs of gear including a 6.5lb rifle and 200 rnds of ammo, etc.) and depletion of essential vitamins, electrolyte imbalance. They were always the first to collapse and have to hear me scold “see I told you so.” An IV of D5W usually does the trick (D is for dextrose, OMG!)
A short-lived increase in seizure frequency may occur during illness or if ketone levels fluctuate. The diet may be modified if seizure frequency remains high, or the child is losing weight.[19] Loss of seizure-control may come from unexpected sources. Even "sugar-free" food can contain carbohydrates such as maltodextrin, sorbitol, starch, and fructose. The sorbitol content of suntan lotion and other skincare products may be high enough for some to be absorbed through the skin and thus negate ketosis.[31]
So rather than giving one-size-fits-all dietary advice or weaponizing the word “balanced” it might be better if the medical community suggested that there are Individual differences that need to be considered. This might also help those lay folk who have had success with one dietary lifestyle or another also realize that what’s valid for them may not be good advice for others.
I tried the keto diet a couple years ago and about 6 weeks in of following it closely I started having significant episodes of lightheadedness and anxiety like symptoms. The coach I was working with said it was keto flu so I continued on the diet for a couple more weeks but it was making life difficult so I stopped. Now every time I try to go low carb the symptoms come back. Sometimes I wonder if it’s just anxiety response or all in my head. I would love to eat low carb but haven’t ever been able to figure out why this happens. I read somewhere that keto can be harder for women’s bodies and affect their adrenal glands. Would this increase anxiety symptoms.

I actually clicked on the story just to see if they included anything about it’s use in managing chronic migraine. I have chronic migraine, basically intractable. Nothing has helped. I’ve tried medications, meditations, and everything in between including a bunch of dietary changes. Keto is my next consideration. I’m happy to hear it helped you! Thanks for sharing


In many developing countries, the ketogenic diet is expensive because dairy fats and meat are more expensive than grain, fruit and vegetables. The modified Atkins diet has been proposed as a lower-cost alternative for those countries; the slightly more expensive food bill can be offset by a reduction in pharmaceutical costs if the diet is successful. The modified Atkins diet is less complex to explain and prepare and requires less support from a dietitian.[55]
Recently, many of my patients have been asking about a ketogenic diet. Is a ketogenic diet safe? Would you recommend it? Despite the recent hype, a ketogenic diet is not something new. In medicine, we have been using it for almost 100 years to treat drug-resistant epilepsy, especially in children. In the 1970s, Dr. Atkins popularized his very-low-carbohydrate diet for weight loss that began with a very strict two-week ketogenic phase. Over the years, other fad diets incorporated a similar approach for weight loss.

It’s a habit to enjoy a brie cheese for desert instead of a piece of chocolate cake but each are favored deserts in France. I’m personally more satisfied after a 350 calorie sized wedge of brie than the same number of calories of cake.. which will give me sugar crash and .. really I’d like two slices of cake(I’ve got a sweet tooth that once I get going it wants to keep being fed)
I actually clicked on the story just to see if they included anything about it’s use in managing chronic migraine. I have chronic migraine, basically intractable. Nothing has helped. I’ve tried medications, meditations, and everything in between including a bunch of dietary changes. Keto is my next consideration. I’m happy to hear it helped you! Thanks for sharing
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.
In many developing countries, the ketogenic diet is expensive because dairy fats and meat are more expensive than grain, fruit and vegetables. The modified Atkins diet has been proposed as a lower-cost alternative for those countries; the slightly more expensive food bill can be offset by a reduction in pharmaceutical costs if the diet is successful. The modified Atkins diet is less complex to explain and prepare and requires less support from a dietitian.[55]
Upon starting the diet, some patients report symptoms like fatigue, headaches, and muscle aches. However, these short-lived symptoms are, in fact, a sign that the diet is working, and the body is switching over from burning glucose as fuel to burning fat. This transition involves upregulating certain enzymes and down-regulating others; it is a profound shift for the human body that can have uncomfortable symptoms. However, these side effect usually last only 3-4 weeks. They can be ameliorated in most cases, by drinking several cups of bouillion broth during the day until the transition is completed.15

The ketogenic diet is an advanced nutritional approach that improves fat burning, preserves lean body tissue and improves brain function. The Ketogenic diet also starves cancer cells of their preferred fuel source (sugar) and allows our immune system to function at it peak. This book goes over all the details and challenges involved with the Ketogenic diet in order to turn your body into a lean, mean fat burning machine. You will find invaluable information in this 10 chapter E-guide that will help you break through challenges you have experienced in the past with the ketogenic diet.


The ketogenic diet is not a benign, holistic, or natural treatment for epilepsy; as with any serious medical therapy, complications may result.[28] These are generally less severe and less frequent than with anticonvulsant medication or surgery.[28] Common but easily treatable short-term side effects include constipation, low-grade acidosis, and hypoglycaemia if an initial fast is undertaken. Raised levels of lipids in the blood affect up to 60% of children[38] and cholesterol levels may increase by around 30%.[28] This can be treated by changes to the fat content of the diet, such as from saturated fats towards polyunsaturated fats, and if persistent, by lowering the ketogenic ratio.[38] Supplements are necessary to counter the dietary deficiency of many micronutrients.[18]
Be aware of the effects of nightshades on your body; while they are permitted in ketosis, they cause inflammatory diseases like rheumatoid arthritis in sensitive people. Nightshades include tomatoes, tomatillos, peppers, okra, and eggplant. For a Bulletproof ketosis, also limit onions and garlic, which tend to be moldy and can disrupt your alpha brain waves. Plus, lightly cook any oxalate-heavy cruciferous and leafy greens.[1]
First appointment: Your first meeting with our team will be a one-hour new patient appointment. You’ll meet our nurse practitioners, social worker and dietitians to discuss the diet’s daily requirements, the initiation process, the length of time your child will be on the diet, how the diet may affect your family and any other questions your family may have. If the ketogenic diet team and your family both agree the diet will be manageable for your family, an initiation is scheduled.

Dr. Campos, it is unfortunate that you retain the medical community’s negative stance on the ketogenic diet, probably picked up in medical school when you studied ketoacidosis, in the midst of an obesity and type II diabetes epidemic that is growing every year, especially among populations who will never see the Harvard Health Letter. The medical community has failed in reversing this trend, especially among children, and the public is picking up the tab, in the form of higher health insurance premiums to treat chronic metabolic diseases which doctors cannot cure. The ketogenic diet does not bid its adherents to eat unhealthy processed meats, and the green leafy vegetables that it emphasizes are important in a number of nutritional deficiencies. People lose weight on the ketogenic diet, they lose their craving for sugar, they feel more satiety, they may become less depressed, their insulin receptors sensitivity is improved, and these are all the good outcomes you fail to mention. There is a growing body of research which demonstrates the neuroprotective effects of the ketogenic diet to slow cancer progression, as well as diseases like Parkinson’s and Alzheimer’s, for which there are no effective medical treatments. Please respect your patients by providing them with evidence-based medical outcomes, not opinions.
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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.

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.
A short-lived increase in seizure frequency may occur during illness or if ketone levels fluctuate. The diet may be modified if seizure frequency remains high, or the child is losing weight.[19] Loss of seizure-control may come from unexpected sources. Even "sugar-free" food can contain carbohydrates such as maltodextrin, sorbitol, starch, and fructose. The sorbitol content of suntan lotion and other skincare products may be high enough for some to be absorbed through the skin and thus negate ketosis.[31]
The other nutritional remedy for T2 diabetes is carbohydrate restriction. In a large, ongoing university-based study, 60% of patients with Type 2 diabetes reversed their diagnosis of diabetes after just one year on a ketogenic diet, supplemented by support via a mobile phone app.11 On this protocol, 94% of participants reduced or eliminated their need for insulin medications while improving the vast majority of cardiovascular risk factors.12

Because it lacks carbohydrates, a ketogenic diet is rich in proteins and fats. It typically includes plenty of meats, eggs, processed meats, sausages, cheeses, fish, nuts, butter, oils, seeds, and fibrous vegetables. Because it is so restrictive, it is really hard to follow over the long run. Carbohydrates normally account for at least 50% of the typical American diet. One of the main criticisms of this diet is that many people tend to eat too much protein and poor-quality fats from processed foods, with very few fruits and vegetables. Patients with kidney disease need to be cautious because this diet could worsen their condition. Additionally, some patients may feel a little tired in the beginning, while some may have bad breath, nausea, vomiting, constipation, and sleep problems.
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