Though intermittent fasting isn't necessarily unhealthy, people with a personal or family history of an eating disorder should steer clear of the diet. The practice also isn't ideal for those who are highly active, since they require more fuel.
"I would encourage people to be very careful exercising while fasting," said Hartley. "Food provides our body with energy for movement, so exercising while fasting may affect performance and also lead to an unhealthy energy deficit."
While Hartley said that no body type is particularly suited to intermittent fasting, she recognized that some people may only experience hunger pangs during a typical 8-hour fasting window. If people are able to fast "in a flexible way that isn't negatively affecting their life or health, that's great," she said.
In general, though, she advises people to eat a meal or snack every 3 to 4 hours.
"Food is our fuel," she said. "Why try to drive a car on an empty tank?"