The ketogenic or "keto" diet encourages eating lots of fat and restricts carbohydrates.
The ketogenic or "keto" diet has been called the holy grail of good health and weight loss by some doctors and bloggers. On the flip side, it's a nutritionist's nightmare.
The keto diet goes against conventional wisdom on health eating. It encourages eating lots of fat and limits carbohydrates to no more than 50 grams a day, the rough equivalent of a plain bagel or a cup of white rice. By comparison, dietary guidelines laid out by the US Department of Agriculture recommend consuming between 225 and 325 grams of fluffy, white carbs a day.
Here's why health nuts in Silicon Valley are saying yes to fat.
It cuts down carbs to between 20 and 50 grams a day, depending on a person's medical history and insulin sensitivity. There are about 30 grams in an apple, for comparison.
On the diet, healthy fats account for roughly 80% of a person's daily calories, while protein makes up about 20%. On average, Americans get about 50% of their calories from carbs, 30% from fat, and 15% from protein, according to the Centers for Disease Control and Prevention.
The human body breaks down carbohydrates into glucose, which is used for energy or stored as glycogen in liver and muscle tissue. But the body has a plan-B fuel supply.
When carbs go missing from a person's diet, the body uses up its glucose reserves and then breaks down stored fat into fatty acids. When fatty acids reach the liver, they're converted into an organic substance called ketones. The brain and other organs feed on ketones in a process called ketosis, which gives the diet its name. Keto-dieters eat lots of fat to maintain this state.
Dr. Jason Fung, who specializes in kidney care, offers an analogy in his book "The Obesity Code": Imagine sitting down to an all-you-can-eat buffet. At some point, the idea of eating one more pork chop becomes sickening. But if the dessert cart passes, it's hard to resist.
That's because highly refined carb-filled foods, like cake and pie, don't trigger hormones in the brain that say, "You're full. Stop eating." Proteins and fat signal when you've had enough.
When we eat carbohydrates, the body churns out a hormone — insulin — that allows the body to use sugar from carbs for food or to store glucose for future use. The absense of carbs in a person's diet causes insulin levels to plummet, and that suppression of insulin leads to weight-loss, according to several studies reviewed by the American Society for Clinical Nutrition.
Mitochondria are the powerhouses of our cells. They take in nutrients and generate energy for the cells. A limited body of research suggests a keto diet may increase the number of mitochondria in brain cells, according to a study written about in Scientific American.
When these "energy factories" are topped off, neurons in the brain may be better able to ward off stress from age-related brain diseases that ordinarily exhaust or kill the cells.
A study of 23 older adults showed that a keto diet may enhance memory in people with mild cognitive impairment. Researchers randomly assigned the adults a high-carb or low-carb diet and observed their ability to memorize words over six weeks. Their findings indicated that very low carbohydrate intake, even in the short term, can improve memory function in older adults.
A different double-blind study assigned 152 patients with mild to moderate Alzheimer's disease either a dietary supplement that injects ketones into the body or a placebo. The subjects maintained a normal diet. Three months later, researchers found that those receiving the drug showed significant cognitive improvement compared to those who received the placebo.
Without carbohydrates, there are no sugar spikes and crashes. I tried the keto diet for two months earlier this year, and it made me feel invincible. Even on days when I ate bunless cheeseburgers for lunch, my energy was sky-high. I drank less coffee and felt more alert.
When you have difficulty focusing or generally getting anything done, you may be experiencing a made-up epidemic called "brain fog." It's brought on by decreased levels of GABA — a neurotransmitter that sends chemical messages through the brain and the nervous system.
Mice that were fed a high-fat, low-carb diet lived longer and maintained their health later in life, according to two independent studies that were recently published in the journal "Cell Metabolism." Researchers at University of California, Davis, observed a 13% increase in median life span for mice on the keto diet. In humans, that would be seven to 10 more years.
More research in humans is required.