Slashing carbs to this degree forces the body into ketosis, a metabolic state in which your body starts to rapidly break down fat for fuel. That sounds better than it feels. During the first few days—sometimes weeks—of ketosis, people often feel tired, irritable, and dizzy and have difficulty sleeping. This carbohydrate withdrawal is often called the “keto flu,” explains registered nutritionist and certified dietitian Dana Notte, MS, director of nutrition at Green Mountain at Fox Run, a healthy-weight retreat known for helping women “detox” from fad dieting. Check out the 13 things everyone gets wrong about the keto diet.
When some people attempt a ketogenic diet, they experience the “keto flu” during the period of time their bodies are adapting to the diet. This is a period of feeling lightheaded, lethargic, irritable, and unmotivated. “It typically lasts one to three days, and may very well be just the result of dehydration. A drop in insulin can impact renal sodium retention such that sodium and fluids are excreted more readily. This also acts to lower blood pressure,” Goss says.
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 keto diet is taking the fad diet arena by storm. Folks are turning to the diet as a means of weight loss, and some believe that it can also help with a slew of health conditions. But even though you may know someone who swears by it, as a dietitian focused on healthy, delicious food, I've never been able to condone such an extreme diet (whether used as a way of life or as a timebound diet to "reset"). (Related: Is the Keto Diet Bad for You?)
Wilder's colleague, paediatrician Mynie Gustav Peterman, later formulated the classic diet, with a ratio of one gram of protein per kilogram of body weight in children, 10–15 g of carbohydrate per day, and the remainder of calories from fat. Peterman's work in the 1920s established the techniques for induction and maintenance of the diet. Peterman documented positive effects (improved alertness, behaviour and sleep) and adverse effects (nausea and vomiting due to excess ketosis). The diet proved to be very successful in children: Peterman reported in 1925 that 95% of 37 young patients had improved seizure control on the diet and 60% became seizure-free. By 1930, the diet had also been studied in 100 teenagers and adults. Clifford Joseph Barborka, Sr., also from the Mayo Clinic, reported that 56% of those older patients improved on the diet and 12% became seizure-free. Although the adult results are similar to modern studies of children, they did not compare as well to contemporary studies. Barborka concluded that adults were least likely to benefit from the diet, and the use of the ketogenic diet in adults was not studied again until 1999.
There are three instances where there’s research to back up a ketogenic diet, including to help control type 2 diabetes, as part of epilepsy treatment, or for weight loss, says Mattinson. “In terms of diabetes, there is some promising research showing that the ketogenic diet may improve glycemic control. It may cause a reduction in A1C — a key test for diabetes that measures a person’s average blood sugar control over two to three months — something that may help you reduce medication use,” she says.