“The most important thing is to make sure that you’re eating enough,” says Yu. “When you don’t have enough fuel—not only to support daily activities of life but to support your exercise—you dig yourself into this hole in which you don’t have enough energy.” 

And when your body lacks nutrients, it starts to shut down other systems to conserve that energy. “That’s why the menstrual cycle can start to get wonky,” she adds, “And that’s why you can see potential impacts on gut health, cardiovascular health, [and] mental health1.” 

Aside from these overall health concerns, you’ll also likely see deficits in performance—seems counterintuitive for someone wanting to enhance their exercise, right? “You’re not going to adapt to your training, you’re not going to recover well, you’re not going to perform well,” says Yu. “You just need to make sure you’re getting enough food in your body to support what you’re doing.” 

She doesn’t encourage any one eating plan—just make sure you’re eating enough. “Make sure you’re eating consistently throughout the day, too,” she adds. You don’t want to dip into too much of an energy deficit at any one point of the day. A deficit of 300 calories can make a difference, and that’s not a lot—that’s a snack.”