What does “keto” mean and what’s the diet like?
“Keto” is short for ketogenesis, which is the production and build-up of ketones. Ketones are a byproduct of fat metabolism, and they are increased when carbohydrates are restricted and the body is forced to rely more heavily on fat as a substrate for energy.
In considering whether to follow a diet that intentionally alters normal metabolism, it is helpful to have some understanding of how the body, and the keto diet, are designed to work.
At rest, our bodies typically burn a fairly even mix of fat and carbohydrates. Protein plays other important roles but is not typically included in the regular energy mix. Despite all the low-carb hype we hear these days, working muscles use carbohydrates for energy, and during exercise the percentage of carbohydrates burned increases with intensity.
Our brains rely entirely on glucose (a simple carbohydrate) for energy. If you have ever experienced the sensation of being “hangry” (when you are so hungry that you get grumpy or have trouble concentrating) then you have felt your brain calling for glucose. As a survival mechanism, in the absence of adequate carbs/glucose, the human brain can also metabolize ketones to keep from starving.
Carbohydrates are stored in the liver and muscles as glycogen. When dietary carbohydrates are restricted, these stores are depleted. The basis of the ketogenic diet is to intentionally deplete these stores by severely limiting carbohydrate intake.
When there are no carbs available, the body is forced to rely more heavily on fat for energy. As fat is metabolized, ketones are produced. Ketones can be “recycled” for energy, but not very quickly. When they are produced faster than they are utilized, ketone levels in the blood rise and are also excreted in urine. This is ketosis.
There are several variations of the ketogenic diet, but traditionally it includes around 15 percent of calories from protein, limits carbohydrate intake to 5-15 percent of total calories (about 20-75 grams per day), with the remaining 70-80 percent coming from fat.
What is the “keto flu” and why does it happen?
The keto flu refers to a series of unpleasant side effects that many people experience as their carbohydrate stores are depleted and their bodies adapt to burning more fat. Symptoms include headache, nausea, bad breath, mental fogginess, muscle cramps, increased heart rate, insomnia, feeling light-headed and lethargy/fatigue.
It can take anywhere from a few days to several weeks for individuals to become “fat adapted” to the ketogenic diet, after which symptoms typically subside.
These symptoms are caused by reductions in blood glucose, the depletion of glycogen stores, and a general shift in metabolism. Water is also stored in the muscles, so as glycogen is used, water is lost. This accounts for the rapid drop in weight many dieters experience when starting keto and the increased risk of dehydration and electrolyte depletion.
What are the benefits of this diet?
Obvious benefits of the keto diet include weight loss, often rapid, especially in the beginning. Fat makes foods taste good and is very satiating, so keto followers enjoy eating and not feeling as hungry as they may have on other diets.
There are a few short studies showing benefits such as improved glucose control, reduced insulin levels and positive changes in cholesterol markers, even on a high-fat diet. This may be the case, but more research is needed to confirm these claims. It is important to note that many of these studies included subjects who were already overweight/obese at the onset. For these individuals, simply losing fat/weight (regardless of how) promotes these desirable physiological changes.
Following a very restrictive diet is challenging, especially when dining away from home. The popularity of this diet makes it more socially acceptable to eat differently than your dining partners.
What are the risks of this diet?
Having the “keto flu” doesn’t sound like fun! The potential for dehydration and electrolyte imbalances can pose a challenge to the kidneys, and it is nutritionally inadequate (more on that below). We have decades of research supporting the fact that high-fat diets pose a risk to our cardiovascular health. Also, long-term compliance on such a restrictive diet is difficult to maintain, both practically and socially.
It sounds like this diet makes people miss out on a lot of nutrients. How can it be healthy?
It does. By eliminating or drastically reducing the consumption of many foods or food groups, long-term adherence to a ketogenic diet is likely to result in inadequate intake of many vitamins, minerals and perhaps fiber. In addition, there is much evidence that high-fat diets, especially those high in saturated fat, increase the risk of many disease states.
As a registered dietitian, I cannot use the word “healthy” to describe this diet. It can be made healthier by including as many vegetables as possible and focusing on unsaturated fats (from nuts, oils, avocados and fatty fish) while limiting saturated fats (from meats, butter and other full-fat dairy foods). One good thing about this diet is that it cuts out simple sugars, which keeps people away from sodas, sweets and fast food.
Who should try this diet, and who should avoid it?
People who need to “jump start” their weight loss efforts may experience the benefit of following this restrictive diet for a limited time. This is a popular diet right now, so individuals who enjoy the social support or online “coaching” that a large group of followers can provide may be attracted to this diet.
Individuals who are insulin resistant may do well with lower carbohydrate intakes, including a ketogenic diet. There is some initial evidence to support a ketogenic diet for diabetic patients, but they should have a discussion with their physician before beginning this diet, as should anyone with kidney disease. It is not appropriate for pregnant or nursing mothers.
What are some healthy meal ideas on a keto diet?
Egg cups with veggies, cauliflower “rice” with veggies and chicken, salads with high fiber vegetables, avocados and salmon.