During a campaign event in New Hampshire this week, the 77-year-old recalled comments by his former White House physician, Ronny Jackson, who previously said he would “be around for 200 years” if he did not eat so much junk food.
Nevertheless, Mr Trump – who is said to have a penchant for Diet Coke – gave himself a clean bill of health, telling supporters that he feels 35, and adding that he feels “cognitively” 20 years younger than he is.
“I feel like I’m about 35 years old. I feel better now than I did 30 years ago,” Mr Trump said.
The former president was then questioned by a sceptical reporter over his assessment of his health, to which he responded: “It’s called genetics. Some people have great genes.”
Both Mr Trump and President Biden have faced attacks over their age, sometimes from each other, and sometimes from members of their party, during the campaign trail.
At an event in October, echoing a common conservative attack line on the president, Mr Trump claimed Joe Biden, who turned 81 last year, “can’t put two sentences together and he’s in charge of nuclear warfare”.
He also mocked Mr Biden’s several falls while on various presidential engagements.
“I see a stairway there, I see a stairway there. If I had to, I’d jump right off this front-end thing – we could make it, it’s about four feet,” he said at the event.
However, Mr Trump, who is just four years younger than the president, has faced questions over his own age.
“This is a different Donald Trump than 2015 and ’16 – lost the zip on his fastball,” Florida governor Ron DeSantis told reporters during a visit to New Hampshire last year.
Mr DeSantis also launched an “accident tracker” to catalogue Mr Trump’s various gaffes.
Meanwhile, former UN ambassador Nikki Haley has called for mental competency tests for politicians over 75.
In November last year, Mr Trump posted a doctor’s note on his Truth Social app, which claimed he was in “excellent health” owing to his “weight reduction”.
It is alleged that Mr Trump has “dropped at least 30 pounds” in recent months, with an “insider” at Mar-a-Lago telling Page Six that he was staying away from the buffet and has not been seen “scarfing down ice cream sundaes or chocolate cake with two scoops of vanilla ice cream on it”.
They credit former first lady Melania Trump for his improved eating habits.