More and more studies show that low-carb diets are an effective way to lose weight: A 2018 report out of Framingham State University found that after five months on a low-carb, high-fat diet, overweight adults burned about 250 more calories daily than people who ate a high-carb, low-fat diet. The keto diet in particular has a number of famous adherents, including Halle Berry, Katie Couric and Gwyneth Paltrow. Kourtney Kardashian blogged about doing keto, calling it “a really positive experience.” And keto-friendly recipes, snacks and meal plans have proliferated in the past few years.
And it’s not just this study, either. Several other studies have found  that keto leaves rodents unable to process carbs,[7] leads to insulin resistance,[8] and, more long-term, causes non-alcoholic fatty liver disease, which is when your liver accumulates lots of fat and begins to shut down.[9][10] Triglycerides and inflammation go way up, too.[11]
There are seemingly endless options to curate a diet to meet every notion or need. However, those living with diabetes may find that these diets don’t always work to balance glycemic control and blood sugar. So what about the ketogenic diet? Is it a fad that will one day be supplanted by the next newest way to eat, or will the science behind it ensure it keeps a lifelong and loyal following? And if the latter, what role can it play in the lives of those living with diabetes?

Since our body isn’t used to using ketones, we tend to feel flu-like when in ketosis. Lots of brain fog, fatigue, headaches, nausea and poor endurance. You also get bad smelling breath, sweat and pee from the acetone (a byproduct of fat metabolism). Sexy? Not so much. Thankfully, if you are in ketosis long enough, a lot of people report that most of these side effects start to go away.
The keto diet is a low-carb, high-fat dietary regimen which has been linked to improvements in insulin sensitivity and higher rates of weight loss — both positive factors in managing type 2 diabetes. Lowering carb intake induces a metabolic state known as ketosis, through which the body produces ketones which burn fat — rather than carbohydrates — for energy.
The catch, of course, is that if it sounds too good to be true, it probably is. And that’s exactly what hopeful dieters need to keep in mind when approaching the ketogenic diet (if we're calling it by its formal name). It’s not that this high-fat, moderate-protein, low-carbohydrate approach to eating can’t deliver weight loss in a delicious package, but it’s a restrictive, sometimes complicated affair that isn’t sustainable for most people.
He was wrong. Originally used for epilepsy, studies show that keto diets are far from dangerous. In fact, they benefit numerous conditions, including cancer, dementia, and overweight/obesity, and modern history only supports these claims. During the early 19th century, physicians had dramatic success implementing keto diets, yet they eventually found that prescribing drugs was much easier that than scrupulously monitoring what people ate. (1) 
More good news: Snacks are totally allowed (and I'm not just talking about carrot sticks). There are plenty of packaged options out there designed for keto fans. FATBAR is one of them. These snack bars have 200 calories, 16 grams of fat, and four grams of net carbs. They're also plant-based and are made with almond or cashew butter, cocoa butter, coconut, pea protein, sunflower seeds, and chia seeds.
As for individuals with type 2 diabetes, Dr. Galati says, "a very low carbohydrate diet could be tolerated, albeit with extreme caution. Transitioning to a ketogenic diet will require several lifestyle changes as well as careful monitoring of both your food intake and glucose levels and adjustments to your medications. Also, you should increase your water consumption." 
Some people just won’t do as well as others on a ketogenic diet. In particular, high energy demand athletes often choose to consume more nutritious carbs than advised per keto guidelines. Females with metabolic damage from a history of yo-yo dieting, or thyroid or adrenal dysfunction, also report difficulty with prolonged carb restriction to promote keto.
“When you start the keto diet, you lose sodium and other electrolytes in the urine due to reductions in insulin,” says Yawitz. “This is a major contributor to symptoms of keto flu.” So it’s important to replenish sodium through the diet, especially if you exercise or sweat a lot. “This can help ward off more serious side effects that are seen with long-term sodium deficiencies,” says Yawitz. These include lethargy and confusion — and in extreme cases, seizures, coma, and death, according to the Mayo Clinic.
Eating slightly more carbs may potentially slow down weight loss and mute rapid, dramatic health improvements, but it can still lead to better health, especially if you are cutting out sugar and processed foods. And keto flu will no longer be an issue. Once you’ve adapted to low-carb eating, feel free to try eating less than 20 grams of carbs again to see whether your body prefers this or slightly higher carb intake.
What is more common throughout the history of the human race is fasting. Islamic Ramadan is a 28- to 30-day fast where food and drink are prohibited during the daylight hours. Christianity also has a strong fasting foundation, and in the Bible, Jesus fasted to have higher and clearer communication with God. Greek Orthodox Christians fast for a total of 150–200 days each year!

Casual chronic keto is at some risk of those same side effects. Sure, there are sporadic anecdotal cases where there appears (so far) to be no harm, but these are not large population RCTs. The KD-in-epilepsy data is closer to being RCT data. There being no ancestral case for chronic keto, we need to learn what we can from the formal studies (and sure, endeavor to separate the ailment, med and diet effects).

After increasing water intake and replacing electrolytes, it should relieve most all symptoms of Keto Flu. For an average person that is starting a ketogenic diet, eating 20-30g of net carbs a day, the entire adaptation process will take about 4-5 days. My advice is to cut your carbs to fewer than 15g to ensure that you are well on your way into ketosis within one week. If you are experiencing any more keto flu symptoms, double check your electrolyte intake and adjust.
"Because cancer cells prefer to use glucose, diets that limit glucose may be beneficial," Barbara Gower, PhD, senior author and professor in the Department of Nutrition Sciences, told Healthline. "Because they limit glucose and several growth factors, ketogenic diets will limit the ability of cancer to grow, which gives the patient's immune system time to respond."

I must tell you when looking at this link they say the American Diabetes Association Guidelines call for 60-75 carbohydrates per meal and that is simply not true. The ADA has recommended since 2013 we use our best clinical judgement in recommending a low carbohydrate diet for people with diabetes, recognizing it needs to be individualized. 60-75 grams is the carbohydrate amount I would give to a very tall, large boned man or perhaps an active teen or young adult. I would never recommend that many carbohydrates for an average size man who was trying to lose weight; he would get 45-60 grams of carbohydrates per meal and 15-30 grams for snacks. A women trying to lose weight would get 30-45 grams of carbohydrates per meal and 15 grams for snacks.
The side effects of extreme low-carb diets are still a mystery. "The first major drawback is the fact that we really don't have any long-term research about how keto followers fare 10, 20, 30 years down the line," Turoff says. "What will the results look like? Will they regain the weight? Will they suffer health consequences? We also thought smoking and diet pills were a good idea, until long-term studies showed us that we were wrong."
Hormonal shifts. By restricting carbs, you will change the balance of glucagon and insulin. This will cause many changes throughout the body, especially regarding the function of your thyroid and adrenal glands. Most people can handle these changes without any issues, but there are a select few that may struggle to adapt without increasing their carb intake.
The research on how diet affects PCOS is minimal, but there is one compelling study on the ketogenic diet and women with PCOS. In this study, five overweight women ate a ketogenic diet (20 grams of carbohydrates or less per day) for 24 weeks. The results were astounding — average weight loss was 12%, free testosterone decreased by 22%, and fasting insulin levels dropped by 54%. What’s even more impressive is that two of the women became pregnant despite previous infertility problems.
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