How Ketosis Works
Originally used to treat epilepsy, the keto diet is now a popular weight loss plan, in part because its focus on fat consumption can leave you feeling fuller and more satisfied than other diets.
When your body depletes the stores of glucose (provided by carbohydrates) that it typically burns for fuel, it starts burning ketones, a form of energy made from fat. It takes a few days to fully enter a ketogenic state, during which a majority of the energy your body uses comes from ketones instead of carbohydrates.
As your body enters ketosis, you may experience side effects collectively referred to as “keto flu.” These symptoms include fatigue, upset stomach, headache, and dizziness, and they’re most common when a person is first entering ketosis. They usually subside once the body has adjusted to burning ketones instead of carbohydrates.
The most accurate way to know if you’re in a ketogenic state is to test your blood or urine using test strips, available at drug stores and online. Handheld breathalyzers can also be used to check ketone levels, but this newer technology isn’t necessarily accurate.
Some people say they feel differently when they’re in ketosis. “You can usually tell,” says Florida-based registered dietitian nutritionist Franziska Spritzler, author of The Low-Carb Dietitian’s Guide to Health and Beauty. “You’re not as hungry.”
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