The 77-year-old former leader made the brash comments while addressing a crowd at a rally in Waterloo, Iowa, on Saturday.
“He’s got a consultant somewhere — this is the worst consultant in politics — that thinks he looks good in a bathing suit, right?” Mr Trump began.
“He spends so much time at the beach. I mean, how do you do that?”
Mr Biden, 80, has previously been pictured in swimming trunks while holidaying at his beach house in Delaware.
Mr Trump went on to detail why he doesn’t partake in similar activity despite his body confidence.
“And, you know, I have a much better body than him,” he said.
“But I’m not really sure that I want to expose it, with the sun blaring down and the sand, the surf, the wind you know.
“I mean, you know, it’s not a pretty sight.”
The comments were quick to inspire backlash online, with one person taking aim at Mr Trump’s apparent attempt to double down on the claim.
“After embarrassing himself by saying he has a better body than President Biden, Trump posts a 40-year-old picture of him playing the rugged, alpha, not at all elite, game of tennis,” the user wrote.
Another user mockingly compared the two men’s body sizes in side-by-side photos.
After making his body quips, Mr Trump went on to say how he would fare against Mr Biden in a fight.
“I think I could go like this,” Mr Trump said while blowing air out of his mouth, “and he’d go down”.
Much of Mr Trump’s past personal criticism towards Mr Biden has been about his age despite there being just three years between the pair.
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