If you have diabetes, it’s important to understand the difference between nutritional ketosis and ketoacidosis. Both involve ketones. But ketoacidosis is a dangerous condition that happens when your body doesn’t have enough insulin and ketones build up too much. Symptoms include excessive thirst, urinating often, confusion, and weakness or fatigue. It’s more common for people with type 1 than type 2.

The ketogenic diet is a high-fat, adequate-protein, low-carbohydrate diet that in medicine is used primarily to treat difficult-to-control (refractory) epilepsy in children. The diet forces the body to burn fats rather than carbohydrates. Normally, the carbohydrates contained in food are converted into glucose, which is then transported around the body and is particularly important in fueling brain function. However, if little carbohydrate remains in the diet, the liver converts fat into fatty acids and ketone bodies. The ketone bodies pass into the brain and replace glucose as an energy source. An elevated level of ketone bodies in the blood, a state known as ketosis, leads to a reduction in the frequency of epileptic seizures.[1] Around half of children and young people with epilepsy who have tried some form of this diet saw the number of seizures drop by at least half, and the effect persists even after discontinuing the diet.[2] Some evidence indicates that adults with epilepsy may benefit from the diet, and that a less strict regimen, such as a modified Atkins diet, is similarly effective.[1] Potential side effects may include constipation, high cholesterol, growth slowing, acidosis, and kidney stones.[3]
You've likely heard horror stories of what competitors feel like when they cut carbs low, or when the average bro talks about going keto. However, the odds are that those people were not actually in nutritional ketosis, or more importantly, following a well-formulated ketogenic diet. Yes, you may experience some fogginess and discomfort, but it doesn't have to be intense if you handle it right.
Heart disease: The diet emphasizes eating a lot of fat. If you eat too much saturated fat (the kind in foods like bacon and butter), that could raise your cholesterol, especially LDL, which is linked to heart disease. This is a special concern for people with diabetes, since the condition itself makes you more likely to get heart disease. Make sure that healthier sources are providing your fats -- the mono- and polyunsaturated kinds, such as those in foods like avocados, nuts, and olive and canola oils. If you do it right, your LDL cholesterol and triglyceride levels could go down. If you take medicine for heart problems, such as high blood pressure, check with your doctor to see if you need to make changes to your medications.
Although you'll be cutting way back on carbohydrates and sugar, some fruits are still okay to eat on the keto diet (though you'll still want to be mindful about quantity in order to remain in ketosis). The fruits that make the cut contain far fewer carbs than their off-limits cousins such as apples, pears, bananas, pineapples, papayas, grapes, and fruit juices in general.
As for if you’re dealing with health issues, you really have to defer to your doctor. For instance, if you have kidney disease, you also want to talk to your doctor about appropriate protein intake. If you have heart disease, you can still go low carb, but you may be better off opting for monounsaturated fats (avocados, nuts, and olive oil) over saturated fats (butter and red meat). Everyone’s cholesterol levels respond differently on a low-carb diet, so if yours are going up, switch to unsaturated sources of fats, Spritzler recommends. “In general, this is a diet most people can do. If you have a chronic condition, work with a doctor who understands low-carbohydrate diets to monitor you,” she adds.
Implementing the diet can present difficulties for caregivers and the patient due to the time commitment involved in measuring and planning meals. Since any unplanned eating can potentially break the nutritional balance required, some people find the discipline needed to maintain the diet challenging and unpleasant. Some people terminate the diet or switch to a less demanding diet, like the modified Atkins diet or the low-glycaemic index treatment diet, because they find the difficulties too great.[42]
Many people take MCT oil and exogenous ketones when they start a Keto diet in order to boost their ketone levels. However, if you’re unused to taking these Keto supplements, then they can cause you to have the runs pretty badly. So make sure to start with a small amount at first (a few grams of ketone salts per day OR 1/2 teaspoon of MCT oil). And then gradually increase your intake as your stomach adjusts to it.
A sudden drop in carbs can lead to a drop in energy levels, with some dieters reporting unusual fatigue, confusion, or brain fog. “The symptoms are from your brain needing to adjust to the new source of energy, while also trying to deal with a drop in electrolyte levels as you lose weight,” says Sharp. It can also cause nausea, stomach pain, cramping, and constipation, as well, due to the diet’s high-fat and low-fiber makeup.

For instance, working with an expert can reduce the risk for dehydration—which can make keto flu symptoms like headache, cramping, nausea, and fatigue worse. Drastically slashing carbs causes the body to excrete a higher volume of water and electrolytes, so you may need to drink more liquids and eat more salt to stay adequately hydrated, Mancinelli explains. How much more is different depending on things like your activity level and age, but a pro can help determine the right amount for you.


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]
Fairly recently, the diet was introduced as a weight-loss diet by an Italian professor of surgery, Dr. Gianfranco Cappello of Sapienza University in Rome. In his 2012 study, about 19,000 dieters received a high-fat liquid diet via a feeding tube inserted down the nose. The study showed an average weight loss of more than 20 pounds in participants, most of whom kept it off for at least a year. The researchers reported a few minor side effects, like fatigue.

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.
Those issues can be part of what's known as the “keto flu,” Warren says. Other side effects of the keto diet, all of which are tied to carb withdrawal, can include lightheadedness, nausea, mental fog, cramps, and headaches, in addition to tiredness. Luckily, the keto flu doesn't usually last more than a week—which is coincidentally about when people start to see the number on the scale go down, says Warren.
Taking an exogenous ketone supplement, such as Perfect Keto can also help reduce keto flu symptoms. Exogenous ketones help fight fatigue and boost energy levels by raising the ketone levels in your blood. To be clear, ketone supplements aren’t a replacement for the keto diet, but they can help you stay in ketosis when you’re meeting your macros, and provide all day energy.
A Cochrane systematic review in 2018 found and analysed eleven randomized controlled trials of ketogenic diet in people with epilepsy for whom drugs failed to control their seizures.[2] Six of the trials compared a group assigned to a ketogenic diet with a group not assigned to one. The other trials compared types of diets or ways of introducing them to make them more tolerable.[2] In the largest trial of the ketogenic diet with a non-diet control[16], nearly 38% of the children and young people had half or fewer seizures with the diet compared 6% with the group not assigned to the diet. Two large trials of the Modified Atkins Diet compared to a non-diet control had similar results, with over 50% of children having half or fewer seizures with the diet compared to around 10% in the control group.[2]
If you’ve recently switched to the keto diet and you’re feeling drowsy, achy, nauseous, dizzy, and irritable, don’t worry. These symptoms are your body’s natural reaction to removing carbs from your diet, and while it may have you second guessing your keto diet decision, we promise you these keto flu symptoms will pass. Stick with it, and soon you’ll be reaping the energizing, fat-burning rewards that come with ketosis.
The most science-backed performance-boosting supplements, such as creatine monohydrate, beta-alanine, and caffeine, are all A-OK on the ketogenic diet. So, if you take a pre-workout, you should be able to continue without issue. I would also recommend gulping down some bouillon before your session to ensure your sodium and magnesium levels are on point.
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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