Ketogenesis, the body process behind one of the biggest current diet trends, promises major, easy weight loss if you can just cut out one food group—carbohydrates.

The ketogenic diet (nicknamed "keto") is named for a state in which the body, starved of energy-efficient carbs, turns to other things for fuel—hopefully burning stores of fat. The low-carb lifestyle has been around for a while, but whereas diets like Atkins emphasized protein consumption, keto ups the amount of fats dieters eat. 

The diet has now become so popular that food companies are creating products—even full meals—to allow dieters to maintain the low-carb, high-fat eating plan. 

In the short-term, “people are loving it,” says Sarasota dietitian Rebecca Henson, who has worked with a lot of “keto dropouts,” as she calls them. “They can have all the butter and the sour cream, all the oils—but they cannot eat carbohydrates.”

But Henson points out that there’s a dearth of studies on the long-term effects of the keto diet, and what we do know about it is, scientifically speaking, not great.

For one thing, there’s no way of knowing if a body in ketosis will focus on burning stored fat as opposed to other possible backup fuels, including muscle. Losing muscle means your weight will go down, but so will your metabolism. If you’re only doing keto on a temporary basis, you’ll be less equipped to burn energy when you go back to a normal diet.

And scientists have been unable to demonstrate the long-term effects of maintaining ketosis because, in part, study subjects haven’t been able to stay on the diet for more than a year. “Carbs make people happy,” Henson admits. 

But a life without pizza is just one discouraging consequence. In addition to lethargy, ketosis can produce unpleasant body odor and bad breath—symptoms also seen in people with eating disorders like anorexia. In ketosis, “Your body is essentially eating itself,” says Henson. “It’s like when you go into a starvation state and your body is not using normal fuel.”

Henson, who did her master’s thesis on the Atkins diet, points out that carb cravings aren’t innately unhealthy. “When we did a feeding study, everybody hated [the Atkins diet],” she says of her post-graduate research. “These were obese subjects, but in the end what they really missed was fruit. They just wanted to eat some healthy carbohydrates.”

Rather than dieting, Henson preaches wholesale but manageable lifestyle changes that balance healthy eating with overall happiness. While there’s no validity in short-term diets that promise to detoxify or otherwise “reset” the body, she says, two weeks of healthy eating can make people feel so good that they’re less tempted by unhealthy choices.

If you want to do keto, Henson suggests a temporary turn at the diet, maybe for three weeks, emphasizing vegetables in addition to the fats. But that’s a big “if.” Asked straight-up if she would ever recommend the keto diet, Henson’s answer comes quickly and without reservation: “No.”