US President Donald Trump mocked a supporter for being overweight at a rally in New Hampshire on Thursday night, after mistaking him for a protester trying to disrupt the event.

"That guy has got a serious weight problem. Go home, start exercising," he said.

The man, Frank Dawson, a former police officer and Navy veteran, took the insult in his stride, telling Fox News: "Everything's good. I love the guy."

A report by a White House doctor in February found the president is clinically obese, though in good health.

Visit Business Insider's homepage for more stories.

US President Donald Trump mocked a supporter for being overweight at a rally in New Hampshire on Thursday night, after mistaking him for a protester trying to disrupt the event.

As Trump was delivering his speech to supporters in the Southern New Hampshire University Arena, in Manchester, protesters started heckling him from one of the stands and were led away by security.

"That guy has got a serious weight problem. Go home, start exercising," Trump said, mocking a man he thought was one of the protesters.

"Got a bigger problem than I do. Got a bigger problem than all of us," Trump added, in an apparent reference to his own weight. "Now he goes home and his mom says: 'What the hell have you just done?'"

It turned out the man Trump singled out for criticism was one of his own supporters, who was trying to alert security and seize a sign from a protester.

As the protesters were being led out, the Associated Press reported he started shaking his fist as a show of support for the president, who thought he was one of the hecklers.

A Trump supporter, right, tries to grab a protester's sign as Trump speaks at a rally, August 15, 2019, in Manchester, New Hampshire. AP Photo/Patrick Semansky

Bloomberg reporter Jennifer Jacobs in a tweet said that Trump had likely mistaken one of his supporters for one of the three protesters being led away.

Fox News later interviewed the man, Frank Dawson, a former police officer and Navy veteran, who took the president's mockery in good spirit.

"I think he thought I was part of it but I wasn't — I was the good part of it," Dawson said. "Everything's good. I love the guy. He's the best thing that ever happened to this country."

Later, Trump called Dawson from Air Force One and left him a voice mail, a White House official told the Washington Post.

Critics were quick to seize on Trump's mockery of the man, and reinforce the point that the president was ruled as being officially obese earlier in the year.

A report from a White House physical released in February found that the president had gained weight and is officially obese, though in good health, weighing 243 pounds.

Trump's fondness for junk food and aversion to exercise is well known, and he reportedly fueled his 2016 presidential campaign on a diet of Diet Coke and McDonald's.