"If you aren't taking in enough calories, your body will get energy from somewhere, and it isn't always from fat," Krissi said. "We are made for survival and this is one of the ways we survive."
Rachel added, "If your exercise session is under two hours, you should focus mainly on hydrating yourself during the workout and stick to eating one to two hours pre- and postexercise." Your preworkout meal should contain carbohydrates and protein — a handful or two of carbohydrate-rich food and 15 to 20 grams of protein should do the trick — and should be eaten one to two hours before training. When exercising for two hours or longer, Rachel said, "You can also consume carbohydrates during your session at a rate of about 30 to 45 grams per hour." She added, "It can also be very beneficial to consume protein during your workout if it is very long, about 15 grams per hour."
"I suggest eating before long cardio sessions so you have the energy to perform, and also allow enough time for [the food] to digest so you don't get sick," Krissi said. If you're running early in the morning right out of bed, she said to nosh on something that digests quickly, such as a banana or half a piece of toast with jam — find what works for you. If eating before running makes you feel sick, then skip it.
Eating after your long cardio session is important for recovery and preventing muscle wasting, Krissi said. "Refuel one to two hours postexercise with around 30 to 40 grams of carbs and 10 to 15 grams of protein," Rachel added.