Even though following an extremely high fat diet can feel like a radical way to eat, “the research looking at ketosis via diet has not shown any real negative consequences when done in the short term,” says Scott Keatley, RDN, of Keatley Medical Nutrition Therapy in New York City. (Ketosis is the natural metabolic state that makes keto lead to weight loss.)
But there have been few long-term studies, adds Kendra Whitmire, a nutritionist and dietitian in Laguna Beach, California, who practices functional and therapeutic nutrition. It’s difficult to definitively say that it’s safe, and it also largely depends on the types of foods you’re eating on a keto diet. (For instance, olive oil is a healthier choice than butter; salmon is healthier than bacon.) That said, following the keto diet properly, and particularly with help from a medical professional, should reduce negative health effects, says Whitmire.