Symptoms of the keto flu include headache, fatigue, dizziness, sleep problems, heart palpitations, cramps, and diarrhea. These side effects usually lessen and eventually resolve in about two weeks. (2) But to lessen the effects of any discomfort, simply consider slowly transitioning onto a ketogenic diet rather than rushing to change your eating habits. By slowly lowering your carbohydrate intake, while gradually increasing your intake of dietary fat over time, you can transition with less of a negative impact and potentially prevent the keto flu.
One thing many people love about keto diet meal plans is that tracking your food is optional. "One of the biggest benefits of the ketogenic diet is that there's no need to meticulously track your calories like you may in other diets," notes Dr. Josh Axe, D.N.M., C.N.S., D.C., founder of DrAxe.com, best-selling author of Eat Dirt, and cofounder of Ancient Nutrition. "Because you're filling up on fat and protein, you're more likely to feel satisfied and energized all day long, which causes you to naturally eat less." This isn't to say that food tracking on keto is discouraged. "Some people may find calorie counting a useful tool to be more mindful and aware of what they're eating, but it's not necessary on the ketogenic diet," says Dr. Axe, but there's no need to get too stressed about hitting a certain caloric goal, especially if you're not trying to lose weight. (Related: The #1 Reason to Stop Counting Calories)
Chasing blood Ketones instead of focusing on hormone signals: "The higher the number means you have more Ketones circulating in your bloodstream, but that does not mean that you are better at burning fat for fuel," Mavridis points out. "You must be in nutritional Ketosis, which is described as being between 1.5 - 3.0 mol/L on the blood Ketone meter. You will know once you are fat-adapted from hormonal signals, and not from higher Ketones on the blood meter," she adds.
Some research suggests that ketogenic diets might help lower your risk of heart disease. Other studies show specific very-low-carb diets help people with metabolic syndrome, insulin resistance, and type 2 diabetes. Researchers are also studying the effects of these diets on acne, cancer, polycystic ovary syndrome (PCOS), and nervous system diseases like Alzheimer's, Parkinson's, and Lou Gehrig's disease.
The biggest lifesaver, though, came at dinnertime. While I'm okay with sticking to a routine during the day, my dinners have to be different each night. So rather than fall into a trap of Googling "Is fill-in-the-blank-food keto?" I turned to HelloFresh. The subscription meal company recently acquired Green Chef, a company that develops gluten-free menus for those following a keto or paleo plan. (Related: What's the Difference Between the Paleo and Keto Diets?) This means that three nights a week, I didn't have to think about whether the foods in my dinner had too many carbs or not enough fat, or go grocery shopping and spend hours reading nutrition labels. (You'd be shocked at how much sugar, a no-go on keto, is hiding in foods that have no need to be artificially sweetened.) All I had to do was pull the fresh ingredients out of the fridge, follow the recipe, and dig in.
"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.
This is a well-known phenomenon with nearly every type of diet: If you relax the rules even a little bit, you suddenly find yourself overeating. Making entire food groups—such as grains, sugar, and other carbohydrates—off-limits helps make them even more attractive, Macri says. This type of reaction goes beyond a psychological reaction—it can also be physical, she says. “Serotonin is one of the feel-good brain chemicals, and when serotonin decreases, such as it does when you’re on a strict low-carb diet, the brain is on high alert for any kind of reward,” she explains. Let some sugar or bread into your diet, and you could be overcome with a desire for more, Macri warns. “This makes it much more likely that you’ll overeat or even binge on those foods.” 
Positive science on ketosis coupled with personal successes passed by word-of-mouth have driven more people to explore the ketogenic diet, says Volek. More recently, the keto diet hints at having a promising therapeutic role in cancer, Alzheimer’s, Parkinson’s and polycystic ovary syndrome (PCOS). Research is still early in many areas, but Volek suspects there will more definitive answers on the wider scope of the diet’s benefits within the next decade.
Y. Wady Aude, MD; Arthur S. Agatston, MD; Francisco Lopez-Jimenez, MD, MSc; Eric H. Lieberman, MD; Marie Almon, MS, RD; Melinda Hansen, ARNP; Gerardo Rojas, MD; Gervasio A. Lamas, MD; Charles H. Hennekens, MD, DrPH, “The National Cholesterol Education Program Diet vs a Diet Lower in Carbohydrates and Higher in Protein and Monounsaturated Fat,” Arch Intern Med. 2004;164(19):2141-2146. http://archinte.jamanetwork.com/article.aspx?articleid=217514.
A ketogenic diet could be an interesting alternative to treat certain conditions, and may accelerate weight loss. But it is hard to follow and it can be heavy on red meat and other fatty, processed, and salty foods that are notoriously unhealthy. We also do not know much about its long-term effects, probably because it’s so hard to stick with that people can’t eat this way for a long time. It is also important to remember that “yo-yo diets” that lead to rapid weight loss fluctuation are associated with increased mortality. Instead of engaging in the next popular diet that would last only a few weeks to months (for most people that includes a ketogenic diet), try to embrace change that is sustainable over the long term. A balanced, unprocessed diet, rich in very colorful fruits and vegetables, lean meats, fish, whole grains, nuts, seeds, olive oil, and lots of water seems to have the best evidence for a long, healthier, vibrant life.
If you need to eat more or fewer calories per day, you can adjust accordingly by simply taking out or adding a bit more of the ingredients already included in a recipe. For example, adding/removing a tablespoon of olive oil or butter will add/remove about 100 calories. If you like or dislike certain recipes, feel free to shift things around. Make sure to keep an eye on the calories so you’re still falling within an acceptable range of your daily goal.

This is a well-known phenomenon with nearly every type of diet: If you relax the rules even a little bit, you suddenly find yourself overeating. Making entire food groups—such as grains, sugar, and other carbohydrates—off-limits helps make them even more attractive, Macri says. This type of reaction goes beyond a psychological reaction—it can also be physical, she says. “Serotonin is one of the feel-good brain chemicals, and when serotonin decreases, such as it does when you’re on a strict low-carb diet, the brain is on high alert for any kind of reward,” she explains. Let some sugar or bread into your diet, and you could be overcome with a desire for more, Macri warns. “This makes it much more likely that you’ll overeat or even binge on those foods.” 
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.
In terms of weight loss, you may be interested in trying the ketogenic diet because you’ve heard that it can make a big impact right away. And that’s true. “Ketogenic diets will cause you to lose weight within the first week,” says Mattinson. She explains that your body will first use up all of its glycogen stores (the storage form of carbohydrate). With depleted glycogen, you’ll drop water weight. While it can be motivating to see the number on the scale go down (often dramatically), do keep in mind that most of this is water loss initially.
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