The popularity of the high-fat, low-carb keto diet for weight loss has skyrocketed. But some underlying mechanisms and other benefits don’t get much attention and aren’t widely understood. Here’s what you need to know.
My body weight has been the same since I was 20— never changes,” says Laurie Steelsmith, ND, a naturopath in Hawaii and author of Growing Younger Every Day. She decided to go on a keto diet not to lose weight, but to experience its eff ects. “After about 3 weeks, I felt fantastic, I had so much energy, and kept going,” she says. After following the diet for two months, Steelsmith started modifying it in a way that maintains improvements.
“I no longer have low blood sugar—ever,” which had been a problem before keto, says Steelsmith. “My tendency was not to eat because I get busy, so I got ‘hangry,’ and then I got irritable, and then I felt crummy,” she recalls. But that cycle is gone. One day after breakfast, she went on a six-hour hike up a mountain. Afterward, she knew it was time to eat but wasn’t very hungry, still had plenty of energy, and mentally felt on top of her game. Before keto, she would have been hungry, and likely hangry, long before the end of the hike.
THE KETO THEORY
The keto diet changes metabolism by shifting the human body’s fuel source from blood glucose to ketones, chemicals the liver makes when fat is burned to generate energy. A perfectly healthy human body could switch from one fuel to the other as needed, much like a hybrid car that uses either gas or electrical power. However, the large amount of carbohydrates that most people eat has broken that switch, blocking fat from being used as an energy source. The keto diet forces the switch to turn on.
“You’re burning fat, which is in your diet, but you’re also opening up pathways that allow you to eat yourself—you can liberate and mobilize fat, and your brain senses that energy,” says Dominic D’Agostino, PhD, a neuroscientist at the University of South Florida who has been researching keto diets and supplements for over 10 years. “If you’re on a really high-carbohydrate diet and you go four or five hours without food,” he adds, “your brain senses an energetic crisis because it doesn’t have quick or easy access to the fat.” If it did, there wouldn’t be a problem.
Fat burning and keto production are also triggered by fasting, which is why people can survive without food for weeks. Intense or prolonged exercise can also trigger temporary ketone production.
WHY KETO TRIGGERS WEIGHT LOSS
Scores of dramatic before-and-after photos, shared online by keto adherents, might give you the idea that there’s something magical about eating a lot of fat. But this isn’t why the keto diet works. “It helps you lose weight, but it does it by calorie restriction, because it helps you regulate your appetite,” says D’Agostino. “It’s really changing brain chemistry,” he adds. “Instead of your appetite controlling you, the diet allows you to control your appetite, to moderate your intake, and to really control what you eat.”
KETO DIET BASICS
The carb content of keto diets is typically counted as net carbs: the amount of total carbs in a food minus its fiber content. Total net carbs per day range between 20 and 50 grams, much lower than the typical American diet, which contains between 200 and 300 grams of total carbs.
No one officially tracks the nation’s net carb consumption, but it’s estimated that we eat an average of 15 grams of fiber daily. Subtracting the fiber from total carbs, average daily net carbs would be around 185 to 285 grams—dramatically higher than keto diet levels.
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