“The most important thing is to make sure you’re eating enough,” Yu says. “When you don’t have enough fuel—not just to sustain your daily activities, but to sustain your exercise—you’re digging yourself into this hole where you’re not getting enough energy”.

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

Aside from these general health issues, you’ll also likely notice a deficit in performance – seems counterintuitive for someone looking to improve their exercise routine, 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 have to make sure you’re getting enough food to support what you’re doing.”

She doesn’t encourage any kind of meal plan—just make sure you’re eating enough. “Also, make sure you eat consistently throughout the day,” she adds. You don’t want to sink into too much of an energy deficit at any point in the day. A 300-calorie deficit can make a difference, and it’s not that much—it’s a snack.”