This means that if you have risk factors for heart disease — such as elevated cholesterol levels, high blood pressure (hypertension), or a strong family history of the disease — you should use caution when following this diet. The diet's heavy reliance on fat, especially saturated fat, can elevate cholesterol levels, further increasing your chances of developing heart disease in the future. (7)
Another difference between older and newer studies is that the type of patients treated with the ketogenic diet has changed over time. When first developed and used, the ketogenic diet was not a treatment of last resort; in contrast, the children in modern studies have already tried and failed a number of anticonvulsant drugs, so may be assumed to have more difficult-to-treat epilepsy. Early and modern studies also differ because the treatment protocol has changed. In older protocols, the diet was initiated with a prolonged fast, designed to lose 5–10% body weight, and heavily restricted the calorie intake. Concerns over child health and growth led to a relaxation of the diet's restrictions.[18] Fluid restriction was once a feature of the diet, but this led to increased risk of constipation and kidney stones, and is no longer considered beneficial.[3]

In 1921, Rollin Turner Woodyatt reviewed the research on diet and diabetes. He reported that three water-soluble compounds, β-hydroxybutyrate, acetoacetate and acetone (known collectively as ketone bodies), were produced by the liver in otherwise healthy people when they were starved or if they consumed a very low-carbohydrate, high-fat diet.[10] Dr. Russell Morse Wilder, at the Mayo Clinic, built on this research and coined the term ketogenic diet to describe a diet that produced a high level of ketone bodies in the blood (ketonemia) through an excess of fat and lack of carbohydrate. Wilder hoped to obtain the benefits of fasting in a dietary therapy that could be maintained indefinitely. His trial on a few epilepsy patients in 1921 was the first use of the ketogenic diet as a treatment for epilepsy.[10]
Normal dietary fat contains mostly long-chain triglycerides (LCT). Medium-chain triglycerides are more ketogenic than LCTs because they generate more ketones per unit of energy when metabolised. Their use allows for a diet with a lower proportion of fat and a greater proportion of protein and carbohydrate,[3] leading to more food choices and larger portion sizes.[4] The original MCT diet developed by Peter Huttenlocher in the 1970s derived 60% of its calories from MCT oil.[15] Consuming that quantity of MCT oil caused abdominal cramps, diarrhoea and vomiting in some children. A figure of 45% is regarded as a balance between achieving good ketosis and minimising gastrointestinal complaints. The classical and modified MCT ketogenic diets are equally effective and differences in tolerability are not statistically significant.[9] The MCT diet is less popular in the United States; MCT oil is more expensive than other dietary fats and is not covered by insurance companies.[3]
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.[3] Few adverse effects have been reported, though cholesterol is increased and the diet has not been studied long term.[47] 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.[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.

Weight loss is the primary reason my patients use the ketogenic diet. Previous research shows good evidence of a faster weight loss when patients go on a ketogenic or very low carbohydrate diet compared to participants on a more traditional low-fat diet, or even a Mediterranean diet. However, that difference in weight loss seems to disappear over time.


Long-term use of the ketogenic diet in children increases the risk of slowed or stunted growth, bone fractures and kidney stones.[3] The diet reduces levels of insulin-like growth factor 1, which is important for childhood growth. Like many anticonvulsant drugs, the ketogenic diet has an adverse effect on bone health. Many factors may be involved such as acidosis and suppressed growth hormone.[37] About 1 in 20 children on the ketogenic diet will develop kidney stones (compared with one in several thousand for the general population). A class of anticonvulsants known as carbonic anhydrase inhibitors (topiramate, zonisamide) are known to increase the risk of kidney stones, but the combination of these anticonvulsants and the ketogenic diet does not appear to elevate the risk above that of the diet alone.[38] The stones are treatable and do not justify discontinuation of the diet.[38] Johns Hopkins Hospital now gives oral potassium citrate supplements to all ketogenic diet patients, resulting in a sevenfold decrease in the incidence of kidney stones.[39] However, this empiric usage has not been tested in a prospective controlled trial.[9] Kidney stone formation (nephrolithiasis) is associated with the diet for four reasons:[38]
“This diet has changed my life. I always find it too easy to cheat because healthy foods are just awful, or so I thought. Once I read the Keto Fit Diet recipes my mouth was watering and I couldn’t wait to get started making these meals. They are delicious, my friends and family would never know I’m on a diet if it weren’t for the 35 lbs I’ve lost in the last 3 months.”
Because some cancer cells are inefficient in processing ketone bodies for energy, the ketogenic diet has also been suggested as a treatment for cancer.[58][59] A 2018 review looked at the evidence from preclinical and clinical studies of ketogenic diets in cancer therapy. The clinical studies in humans are typically very small, with some providing weak evidence for anti-tumour effect, particularly for glioblastoma, but in other cancers and studies, no anti-tumour effect was seen. Taken together, results from preclinical studies, albeit sometimes contradictory, tend to support an anti-tumor effect rather than a pro-tumor effect of the KD for most solid cancers.[60]
According to Macri, “If somebody is looking for physical and psychological health, the best way to get there is to focus on health. That entails eating in balance, not restrictively; moving regularly; and looking at the role of stress in one’s life. Those three areas will get someone to health as well as happiness.” Check out the 13 things doctors want you to know about the keto diet.
A ketogenic diet also has been shown to improve blood sugar control for patients with type 2 diabetes, at least in the short term. There is even more controversy when we consider the effect on cholesterol levels. A few studies show some patients have increase in cholesterol levels in the beginning, only to see cholesterol fall a few months later. However, there is no long-term research analyzing its effects over time on diabetes and high cholesterol.
The American Heart Association’s recommendations for controlling cholesterol include getting more fiber and limiting your intake of saturated fat, both of which would be extremely difficult on a ketogenic diet. While it’s true that research around saturated fat is still evolving, making room for good sources of fiber and unsaturated fats, which reduce the risk of cardiovascular disease, and allowing for a more balanced intake of nutrients, is ideal. In any case, you should check with your doctor before you start a ketogenic (or any new) diet, especially if you have any health conditions like high blood pressure or high cholesterol.
But it's not just the flavor factor. This high-fat, moderate-protein, and very low-carb diet (which is usually broken down as 70 to 75 percent fat, 20 to 25 percent protein, and 5 to 10 percent carbs) can actually leave you feeling physically ill, especially in the beginning. After a week or two on the diet you will enter full ketosis. But until you get there, symptoms like extreme fatigue (the feeling like you can't get out of bed) and the keto "flu" may occur. The keto "flu" is the time where your body is adapting to using ketones as energy, which can leave you feeling nauseated, with headaches, and a foggy head.
When you eat foods high in carbohydrates and fat, your body naturally produces glucose. Carbohydrates are the easiest thing for the body to process, and therefore it will use them first – resulting in the excess fats to be stored immediately. In turn, this causes weight gain and health problems that are associated with high fat, high carbohydrate diets (NOT keto).

One of the most common side effects of starting the ketogenic diet is the “keto flu.” This term describes the often unpleasant, fatigue-inducing symptoms that occur as the body adjusts from a high-carbohydrate to a low-carbohydrate diet. During the keto flu, the body’s stored glucose begins depleting, and the body starts adapting to producing and utilizing ketones as energy. (2)
Meat – like grass-fed selections – and fresh veggies are more expensive than most processed or fast foods. What you spend on Keto-friendly foods will vary with your choices of protein source and quality. You can select less-expensive, leaner cuts of meat and fatten them up with some oil. Buying less-exotic, in-season veggies will help keep you within budget.
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