"The keto diet is primarily used to help reduce the frequency of epileptic seizures in children. While it also has been tried for weight loss, only short-term results have been studied, and the results have been mixed. We don't know if it works in the long term, nor whether it's safe," warns registered dietitian Kathy McManus, director of the Department of Nutrition at Harvard-affiliated Brigham and Women's Hospital.
In the first week, many people report headaches, mental fogginess, dizziness, and aggravation. Most of the time, this is the result of your electrolytes being flushed out, as ketosis has a diuretic effect. Make sure you drink plenty of water and keep your sodium intake up.6One of the fathers of keto, Dr. Phinney, shows that electrolyte levels (especially sodium) can become unbalanced with low carb intake.
"Depending on your approach, [keto diets] can contribute to significant lean body mass loss along with fat loss," said Melinda Manore, a professor of nutrition at Oregon State University. (Typically, dieters want to shed only fat, not lean body mass, which includes muscle.) And as with other fad diets, people typically regain the weight once they go off the diet.
I am trying to get back into keto. I did it before and I was so happy when I lost 10lbs (I did the keto for a month). I am ready to go back to this lifestyle. All this information is very helpful, I have written it all down so it can be easier for me to remember what is allowed and what is not. Looking forward to get back on this keto journey. Thank you for all the great info.
Over 8–10 mmol/l: It’s normally impossible to get to this level just by eating a keto diet. It means that something is wrong. The most common cause by far is type 1 diabetes, with severe lack of insulin. Symptoms include feeling very sick with nausea, vomiting, abdominal pain and confusion. The possible end result, ketoacidosis, may be fatal and requires immediate medical care. Learn more
On the ketogenic diet, carbohydrates are restricted and so cannot provide for all the metabolic needs of the body. Instead, fatty acids are used as the major source of fuel. These are used through fatty-acid oxidation in the cell's mitochondria (the energy-producing parts of the cell). Humans can convert some amino acids into glucose by a process called gluconeogenesis, but cannot do this by using fatty acids.[57] Since amino acids are needed to make proteins, which are essential for growth and repair of body tissues, these cannot be used only to produce glucose. This could pose a problem for the brain, since it is normally fuelled solely by glucose, and most fatty acids do not cross the blood–brain barrier. However, the liver can use long-chain fatty acids to synthesise the three ketone bodies β-hydroxybutyrate, acetoacetate and acetone. These ketone bodies enter the brain and partially substitute for blood glucose as a source of energy.[56]
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]
It is possible to combine the results of several small studies to produce evidence that is stronger than that available from each study alone—a statistical method known as meta-analysis. One of four such analyses, conducted in 2006, looked at 19 studies on a total of 1,084 patients.[23] It concluded that a third achieved an excellent reduction in seizure frequency and half the patients achieved a good reduction.[18]
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]
Lots of apps and websites offer keto diet challenges—basically, a blueprint for the keto diet with a fixed starting and ending point (they typically last for a week to a month, though some may be longer). Speaking of apps, plenty of keto-centric ones are right at your fingertips (a.k.a., your smartphone), like the KetoDiet app, which can help you calculate your macros and track your keto diet effectively.
You’re very welcome, Judy! I’m glad it’s helpful. If you are keto (as opposed to low carb), unfortunately peaches would not allow you to stay in ketosis. You can check my keto food list to help determine what is keto friendly. Of course, there are worse things than fresh fruit 🙂 but in the end our bodies still see the sugar. That being said, it doesn’t mean you sabotaged the whole day. Just pick up again – you got this!! (And for next time, try some fresh berries in moderation when you’re craving fruit.)
Achieving ketosis is a pretty straightforward, but it can seem complicated and confusing with all of the information out there.4If you want to learn more about ketosis and the scientific process around it, you can visit a very in-depth discussion about on Dr. Peter Attia’s website. Here’s the bottom line on what you need to do, ordered in levels of importance:
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.
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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.
Although many hypotheses have been put forward to explain how the ketogenic diet works, it remains a mystery. Disproven hypotheses include systemic acidosis (high levels of acid in the blood), electrolyte changes and hypoglycaemia (low blood glucose).[19] Although many biochemical changes are known to occur in the brain of a patient on the ketogenic diet, it is not known which of these has an anticonvulsant effect. The lack of understanding in this area is similar to the situation with many anticonvulsant drugs.[56]
Radical diets like keto bring radical change, and I’m not referring to pounds you might shed from depriving your body of an essential macronutrient; I’m talking about changes in your social world, your relationship with food, and your mental health. I’m talking about the diet industry convincing us that if we pass on eating out with friends to do our at-home cardio fat-busting workout before roasting another variation on a chicken dinner, we’re going to feel joyous and at peace with ourselves once we reach our fitness “goals.” And we’re actually going to keep the weight off.

Although many hypotheses have been put forward to explain how the ketogenic diet works, it remains a mystery. Disproven hypotheses include systemic acidosis (high levels of acid in the blood), electrolyte changes and hypoglycaemia (low blood glucose).[19] Although many biochemical changes are known to occur in the brain of a patient on the ketogenic diet, it is not known which of these has an anticonvulsant effect. The lack of understanding in this area is similar to the situation with many anticonvulsant drugs.[56]
It’s tough to find keto criticism in a world of trend-driven search engine optimization, so I was positively delighted to find James Fell’s article “Keto Is the Dumbfuck Diet Du Jour, But That Won’t Last.” Turns out he’s been featured in The Washington Post, The Guardian, Chicago Tribune, and Men’s Health, and has committed a decade to diet myth-busting after watching his mother struggle with her weight all his life. I gave him a call after reading his poem “Much Ado About Stuffing.”
While it’s true that low-carb diets do raise the so-called bad LDL-cholesterol in some people, it’s important to note that LDL-C, when influenced by diet, has never been shown to have any effect on cardiovascular risk. Large clinical trials and observational studies show that one’s level of LDL-C and the lowering of LDL-C through diet is not reliably linked to cardiovascular outcomes.21, 22, 23

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.
Selecting the right food will be easier as you become accustomed to the Keto approach. Instead of lean meats, you’ll focus on skin-on poultry, fattier parts like chicken thighs, rib-eye steaks, grass-fed ground beef, fattier fish like salmon, beef brisket or pork shoulder, and bacon. Leafy greens such as spinach, kale and lettuce, along with broccoli, cauliflower and cucumbers, make healthy vegetable choices (but you’ll avoid starchy root foods like carrots, potatoes, turnips and parsnips). You can work in less-familiar veggies such as kohlrabi or daikon.
"Depending on your approach, [keto diets] can contribute to significant lean body mass loss along with fat loss," said Melinda Manore, a professor of nutrition at Oregon State University. (Typically, dieters want to shed only fat, not lean body mass, which includes muscle.) And as with other fad diets, people typically regain the weight once they go off the diet.
During my private and group therapy sessions I learned a lot of information that would be beneficial to the average dieter. My first therapy assignment was to go out and buy a food I used to enjoy, so I purchased M&Ms and relearned how to allow myself a little bit each day. I learned that binges are triggered not by enjoyment of a food but by the feeling that you should stop eating and can’t. I was taught about intuitive eating, which helped me break down my regimented eating schedule and lean into my natural inclination to seek variety of foods in order to reduce cravings. You can find all of these materials online.
People seem to expect, based on fitness guru promises, that being in a state of ketosis feels like a cognition-enhancing, energy-stimulating power hour whereby your waist measurement is negatively correlated with your IQ. I usually just felt fatigued as hell if I tried to exercise, beating my body to death on an aged and grating stair climber at 6am. Then I went about the day eating random assortments of protein and fat, felt totally out of control at the sight of brownies in the office, overdid coffee to suppress my cravings and increase my metabolism, and went to bed feeling the dull ache of deprivation underneath my dieting high. And that was only the beginning.
Here’s what we do know: The keto diet may be useful in treating symptoms of epilepsy, a seizure disorder. “The use of keto in treating epilepsy has the most evidence,” Angelone says. One study conducted by Johns Hopkins Medicine, for example, followed epileptic patients on the keto diet and found that 36 percent of them had a 50 percent reduction in seizures after three months on the diet, and 16 percent were seizure-free. However, experts aren't entirely sure why the keto diet has this affect, she adds.
During my private and group therapy sessions I learned a lot of information that would be beneficial to the average dieter. My first therapy assignment was to go out and buy a food I used to enjoy, so I purchased M&Ms and relearned how to allow myself a little bit each day. I learned that binges are triggered not by enjoyment of a food but by the feeling that you should stop eating and can’t. I was taught about intuitive eating, which helped me break down my regimented eating schedule and lean into my natural inclination to seek variety of foods in order to reduce cravings. You can find all of these materials online.
Hi Mel, Assuming that your ranch dressing doesn’t have sugar added, you don’t need to worry too much about limiting it, but within reason. This is my homemade ranch dressing recipe, which has 0.9g net carbs per 2-tbsp serving. It would be hard to find a store bought one with much less than that, even though some round anything less than 1g down to 0g, which isn’t truly accurate. Also, keep in mind that if weight loss is your goal, some people find that too much dairy can cause a stall. Finally, make sure you aren’t using all your “available” carbs on ranch dressing – have it with some low carb veggies!
In its 2016 report “Healthy Eating Guidelines & Weight Loss Advice,” the Public Health Collaboration, a U.K. nonprofit, evaluated evidence on low-carbohydrate, high-fat diets. (The Keto diet falls under the LCHF umbrella.) Among 53 randomized clinical trials comparing LCHF diets to calorie-counting, low-fat diets, a majority of studies showed greater weight loss for the Keto-type diets, along with more beneficial health outcomes. The collaboration recommends weight-loss guidelines that include a low-carbohydrate, high-fat diet of real (rather than processed) foods as an acceptable, effective and safe approach.
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