During the first season of "The Flash," Barry Allen (Grant Gustin) learned how to tap into all kinds of superhuman speed powers, from punching bad guys at supersonic speeds to warping the flow of time itself. And as we saw when he first met Jay Garrick, the Flash of the alternate reality Earth-2, he still has plenty of tricks up his sleeve -- or should we say, lightning bolts?

But we also learned early on in the show that The Flash can't do it all on an empty stomach; he needs to eat high-calorie protein bars (baked to perfection by Cisco Ramon, of course) so he doesn't completely pass out while running. This added a much needed dose of realism to The Flash's fantastical power set, but the show never really addressed it after that episode, which leads us to believe that Barry hasn't had any problems with lightheadedness since then and knows exactly what he needs to eat to keep his metabolism up. But how much is that exactly?

To figure out just how many calories The Flash would need to consume to, you know, "become the impossible," MTV News spoke to an expert: Dr. Scott Weiss, a sports physician who works at the Bodhizone for Human Performance and Sports Physical Therapy. He told us that while the "calories burned" marker on your treadmill might suggest otherwise, tracking the exact amount of calories you burn while running requires some pretty precise calculations.

"The amount of calories you burn through an activity is directly related to the weight that you have, the speed that you’re going and the duration that you do it for," Dr. Weiss said over the phone. "So when you add those variables together... you will get a pretty close estimation of how many calories a person will burn in that activity and how much they would need for that activity. There are so many calculations that go into it but when you know the person, their weight is the most important thing, the time, the intensity, and the duration, that’s all you need."

Obviously we couldn't call up Grant Gustin and ask him how much he weighs, because that would be pretty rude. But according to the Internet he's about 6 foot 2, so we guessed that he's probably about 190 lbs, which would put him in a pretty average weight range.

With these estimates in place, if The Flash were to run at the speed of sound (767 miles per hour) for just 5 minutes, he would burn a whopping 8,889 calories -- meaning he needs to have a minimum of 10,000 calories in his body before he starts running.

If we're putting it in terms of food Barry Allen likes, that's like 33 salmon avocado sushi rolls in one sitting. Yeesh.

Need a real-life comparison? Dwayne "The Rock" Johnson told Muscle and Fitness back in April that he eats 4,131 calories a day, and he spends over two hours of every day working out and burning those calories off. According to this, the Flash can burn more than twice that in one fortieth of the time.

But that's not all! Running at the speed of sound for 20 minutes would burn almost 70,000 calories -- and if Barry were running at the speed of light (671 million miles per hour) for five minutes, he would burn something like 8 billion calories. And that's not even factoring in how many calories he would burn while at rest, Weiss noted. "If you include his Basal Metabolism, plus what he does to expend his energy, that’s a lot of calories."

So how many of those protein bars would Barry Allen have to eat to keep that up? Definitely more than Cisco Ramon can make, that's for sure.

"I would imagine he’d have to be eating all day long," Weiss said. "he’d have an intravenous drip of food that he’d need to have as he’s sleeping and as he’s awake... Lucky for him, burning that amount of calories in 5 minutes, he can burn whatever the hell he wants. He can have three [pizza] slices downtown, then go uptown for some ice cream. The Flash is a lucky guy."

If you ask us, that doesn't actually sound like a whole lot of fun. But at least he could teach that guy who ate 11,000 calories worth of ice cream in 15 minutes a thing or two, that's for sure.