The keto diet has exploded in popularity over the last several years. Although it's controversial among dietitians, the keto diet has helped people lose weight and transform their lives. The diet is a high-fat, moderate-protein, extremely low-carbohydrate diet.
But for the keto diet to work as it's designed, your body has to get into ketosis. Ketosis is a metabolic state by which your body burns fat for fuel instead of carbohydrates. The body produces ketones in the liver to use as energy, hence the name ketosis. Normally, your body uses carbohydrates (or glucose) as its primary source of fuel. In ketosis, on the other hand, carbohydrates are so low that the body must burn fat.
As Catherine Metzgar, PhD, RD, and a member of the clinical team at Virta Health, explained, there are two ways to get into ketosis: starvation ketosis and nutritional ketosis.
What Is Starvation Ketosis?
"If the body depletes glycogen stores enough, it will move on to burning fat to fuel the body and the brain," Dr. Metzgar said. When someone isn't eating for a long enough period of time, their glycogen stores get depleted, so the body has two choices: burn stored fat, or break down the protein in muscles for fuel. The body will turn to fat before muscle, Dr. Metzgar explained, and that is when someone enters starvation ketosis.
Although intermittent fasting and the keto diet are often done in conjunction with each other, in order for starvation ketosis to kick in, Dr. Metzgar said someone would need to fast for a week to burn fat for fuel, which is obviously not recommended.
"Starvation ketosis is not something to strive for and can actually result in loss of lean muscle mass, so I would not recommend long-term fasting to reach this starvation state if one's goal is to achieve ketosis," she said.
What Is Nutritional Ketosis?
Nutritional ketosis, on the other hand, is what you achieve when you are following the keto diet correctly.
"If dietary carbohydrates are kept low enough for long enough and dietary fats make up 70 to 80 percent of the macronutrient profile, the body mimics starvation," Dr. Metzgar explained. "In this way, a person can still consume calories and deplete glycogen stores enough to get the body to switch to fat."
She recommends that your macronutrient breakdown on the keto diet be about 80 percent fat, 15 percent protein, and five percent carbs. To get into nutritional ketosis, the total carb intake should be about 50 grams or fewer, although every person is different and may need to make some adjustments.
So, Which One Is Better?
Dr. Metzgar's clinical opinion is that nutritional ketosis is the safer way to get into ketosis because prolonged periods of fasting can be dangerous, especially if you have a history of hypoglycemia (low blood sugar) or are taking blood pressure medication. Plus, people who have a history of disordered eating may find this level of fasting triggers a harmful relationship with food and restriction.
"To get into ketosis nutritionally, fat intake does need to increase, but that doesn't mean you need to start taking shots of olive oil and eating sticks of butter," she said. "In my practice, most people need to make slight modifications to increase their fat intake, but primarily, the biggest change is cutting carbs."