Maybe that carbo-load is really full of bull.

I was pretty confident that a low-carb diet would help me to a fast finish at the United NYC Half Marathon on Sunday – but I wasn’t expecting to shave my personal record by nearly 5 minutes. I finished in 1 hour and 33 minutes, averaging 7-minute, 6-second miles.

And the best part of it all was not needing to stuff my gut with globs of glucose gels or sugary sports drinks to get me to the finish line in 1 hour and 33 minutes — a practice that had made my stomach sick for years.

It should be noted, however, that running my fastest 13.1-mile race was a lot more involved than just skipping out on spaghetti dinners in the nights leading up to the race. For months, I followed a strict diet and logged dozens of training miles every week.

“You don’t do low-carb casually,” Dr. Stephen Phinney, a medical researcher who specializes in low-carb nutrition, tells The Post. “You really have to find someone who has the knowledge . . . it’s something you have to take seriously.”

Phinney – who co-authored “The Art and Science of Low Carbohydrate Living” with his colleague, Jeff Volek – has spent decades studying the effects of a low-carb, high-fat diet in endurance athletes. Phinney’s work, along with a growing body of research, suggests that the human body can sustain high-intensity workouts for longer periods of time by using calories stored in fat, not the glycogen stores that most runners use and are loaded with a ton of carbs and sugar before a race.

It’s not that carbohydrates don’t work — they do, up until a point. The glycogen well they create in your body taps out at about 2,000 calories, making glucose gels or sports drinks necessary to cross the finish line in any long-distance run.

But if your body is trained to fuel itself using your fat, you have a tank of about 40,000 calories to keep your engine humming — helping you to run faster and longer.

The only problem: It takes weeks, even months, to become keto (short for ketogenic) -adapted, which is Phinney’s term for the body’s ability to burn fat as a primary fuel. And it all starts with cutting carbohydrates and sugar from your diet — cold turkey.

It’s not easy, either. You’ll feel tired and sluggish; you’ll want to walk instead of run; you’ll crave nothing more than baguettes and doughnuts. And. if you’re like me, you’ll have the added challenge of doing it all as a vegetarian.

“But that energy is usually gained back in four to six weeks,” Phinney says, adding that a few weeks on a carb-restrictive diet forces the body to start using fat as its main energy source.

After two months of following a low-carb diet – and following the guidance of the Howard Beach Comprehensive Health Care Center – I managed to bounce back tenfold from the fatigue I had initially experienced by removing carbohydrates from my meals.

My running speeds increased, too, as I tapped into that newly found energy to maintain my midweek workouts and to keep up with members of the Gotham City Runners – some of the most talented athletes in the city – for weekend-long runs across the five boroughs.

I also lost weight, which made me lighter on my feet. And, because I wasn’t stuffing my face with foods (carbs) that cause inflammation, I recovered quickly after my hardest runs.

“Keto-adapted athletes aren’t just telling us, they’re demonstrating this: Their recovery time is incredibly fast,” Phinney says.

He adds that more professional athletes, including LeBron James, Lindsey Vonn and Carmelo Anthony, are learning the benefits of a low-carb diet, making him just a little grateful that his extensive research is finally starting to hit the mainstream.

“I’m kind of getting released from academic Siberia,” he says with a laugh.