The main criticisms include fears about fat intake and the process of ketosis.The argument over whether saturated fats are unhealthy has been settled in the research literature (they are not). If you need more info, there are several good books to read on this subject.  For more information about the type of fats to eat, see the saturated vs unsaturated fats page.  The right side column on that page has books which provide more information.

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.[18] 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.[30]
A systematic review in 2016 found and analysed seven randomized controlled trials of ketogenic diet in children and young people with epilepsy.[2] The trials were done among children and young people for whom drugs failed to control their seizures, and only one of the trials compared a group assigned to ketogenic diet with a group not assigned to one.[16] The other trials compared types of diets or ways of introducing them to make them more tolerable.[2] Nearly 40% of the children and young people had half or fewer seizures with the diet compared with the group not assigned to the diet. Only about 10% were still on the diet after a few years.[2] Adverse effects such as hunger and loss of energy in that trial were common, with about 30% experiencing constipation.[16]
When it comes to starting the keto diet (or any diet for that matter), there's one thing all experts agree on. You *must* have a plan. "Never try to wing a keto diet," says Julie Stefanski, R.D.N., C.S.S.D., L.D.N., a dietitian based in York, PA, who specializes in the ketogenic diet. "Set a start date and get prepared by reorganizing your pantry, planning out meal and snack options, and purchasing appropriate foods and dietary supplements," she says. "The biggest reason people have a hard time sticking with keto is that people don't have enough interesting foods to turn to, and high-carb favorites win out over good intention. If you didn't buy foods at the grocery store that fit the guidelines, there won't be an easy option in the fridge when you really need it." (A great place to start is this List of High-Fat Keto Foods Anyone Can Add to Their Diet.)
We all know fat is more filling than carbs, but every now and then you get a hankering for something to snack on and you NEED some low carb snacks. Whether it’s salty, sweet or frosty, we all need a moment to enjoy something in between meals. Being on a diet shouldn’t mean all snacks are thrown out the window, being on a diet means learning what your body needs and how to best provide for it. If your body is craving something salty, there are ways of indulging without setting yourself back. There are ways of eating even brownies and cakes that won’t undo all your progress.
During the 1920s and 1930s, when the only anticonvulsant drugs were the sedative bromides (discovered 1857) and phenobarbital (1912), the ketogenic diet was widely used and studied. This changed in 1938 when H. Houston Merritt, Jr. and Tracy Putnam discovered phenytoin (Dilantin), and the focus of research shifted to discovering new drugs. With the introduction of sodium valproate in the 1970s, drugs were available to neurologists that were effective across a broad range of epileptic syndromes and seizure types. The use of the ketogenic diet, by this time restricted to difficult cases such as Lennox–Gastaut syndrome, declined further.[10]
Note that the U.S. Department of Agriculture advises against cooking frozen chicken in a slow cooker or crock pot because slow cookers cook at a low temperature and may not heat chicken up to 165F, which is the minimum temperature to destroy any dangerous bacteria and ensure that chicken is fully cooked. So if you’re using a crock pot or slow cooker to make Crack Chicken, make sure to defrost it first!

Avocado’s are a huge staple food for most keto dieters and we’re no different. You might be able to find a good deal on premade guacamole though. If that’s the case, feel free to go for that and sub out the avocado. If you don’t like broccoli or cauliflower you can try mushrooms or zucchini. If you don’t like any of those you should probably learn to like vegetables!!! But you could also just double down on the salad.

This shopping list and meal plan can be heavily substituted to meet your needs. The first thing you’ll want to do is scan it over and make sure you like eating all of the foods listed here. Eating delicious foods is a big part of adhering to a diet long term! If there is a particular item you can’t stand just do a bit of research and find a substitution. Just make sure the item you decide to substitute in is similar in nutrition to the one you’re eliminating. This can be done with a quick google search or by using a website like My Fitness Pal.
Yes, too much lean protein—think turkey and chicken—even lean fish—if you’re consuming that and vegetable only, without fat there, you are at risk of throwing yourself out of ketosis. Even eating egg whites without yolks greatly spikes insulin. So look to fatty proteins. Fatty cuts of beef, chicken WITH skin, fattier cuts of beef, lamb, and game. Chuck as opposed to 10% lean sirloin.

So you've decided you want to try out the high-fat, low-carb diet, better-known as the fat-burning ketogenic diet. Whether it's to lose weight, have more energy, or fuel workouts differently, going keto is a popular choice right now. But figuring out a keto meal plan on your own is no easy feat, especially since eating a diet super high in fats doesn't come naturally to many people who are accustomed to the traditionally carb-heavy American diet. (It's especially hard if you're vegan and want to try keto.) But this should help: Keto experts explain how to set yourself up for success, plus provide ideas for exactly what keto foods to eat when you're first getting started. (While you're at it, check out these Low-Carb Keto drinks That Will Keep You in Ketosis.)
There is scientific evidence that supports the use of a ketogenic diet to help manage certain neurologic conditions. There are also medical, nutrition, and fitness professionals that recommend the eating program for patients and clients who have other health goals. But just because the program works for some, doesn't mean that it's the best diet for you.
Diarrhea can also be due to a lack of fiber in the diet, says Kizer, which can happen when someone cuts way back on carbs (like whole-grain bread and pasta) and doesn’t supplement with other fiber-rich foods, like vegetables. It can also be caused by an intolerance to dairy or artificial sweeteners—things you might be eating more of since switching to a high-fat, low-carb lifestyle.

Here's the reality: A high carb diet drives up blood sugar and insulin levels. All that sugar and insulin are inflammatory. The standard American diet offers lots of foods that are high sugar AND high in saturated fat, and in studies, these two factors were lumped together. So although saturated fat is healthy, it got the blame for the inflammation that causes heart disease because it was studied in combination with a high carb diet. A ketogenic diet plan which is high in saturated fat and very low in carbohydrate will REDUCE inflammation. (Reference here.)
Bread probably isn’t the first thing that comes to mind when you think about the ketogenic diet because it’s generally full of carbs. But, if you replace your store-bought bread with a homemade keto bread recipe, it can fit seamlessly into your keto low-carb, high-fat diet. How does bread even become keto-friendly? With almond flour, a lot of eggs, cream of tartar, butter, baking soda and apple cider vinegar.

If you’re not sure after your initial test, explore other healthy diets such as clean eating and always have in mind that your number 1 goal should be to avoid overly processed foods (keeping this definition fairly broad of course, as we live in the 21st century and have to adapt to modern age as well, where hardly any of us have time to spend 12 hours a day evolving around food production, gathering and cooking).
There are many ways of implementing a low carbohydrate, ketogenic diet plans but most involve following a higher fat, moderate protein, low carb food plan.  (The Atkins diet is one of the most famous ketogenic diets, but certainly not the only one).  Many people think of ketogenic diets as high protein diets but this is incorrect. They are moderate protein diets.
If you’re looking to get a jump start on your health and fitness goals this year, you may be thinking about trying the ketogenic diet. Maybe you’ve heard the phrase before — it’s a huge diet buzzword — but aren’t sure what it means. Here’s a primer: The ketogenic diet is an eating plan that drives your body into ketosis, a state where the body uses fat as a primary fuel source (instead of carbohydrates), says Stacey Mattinson, RDN, who is based in Austin, Texas.
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