The Prime Minister admitted he was “too fat” after battling coronavirus in intensive care last year. He embarked on a health kick which saw him go running in the morning with rescue dog Dilyn and hire celebrity personal trainer Harry Jameson.
But The Times has cited friends as saying the exercise was not enough for Mr Johnson, who weighed 15st 7lb before being admitted to hospital in April, to lose the weight.
One friend told the newspaper: “He’s been doing it [a fasting diet] on and off for a year or so.
“He sometimes skips breakfast or lunch.”
Another said the Prime Minister frequently skips lunch and sometimes has a “gruesome-looking soup” in the evening.
They added: “It can make him a bit grumpy but it’s working.”
However, a No 10 insider disputed the claims, saying: “This account does not reflect the Prime Minister’s diet.”
Express.co.uk has contacted Downing Street for comment.
Mr Johnson opened up about his weight in a candid video posted on Instagram last July.
“I’m only about 5ft 10 at the outside and I was too fat.
“I start the day by going for a run with the dog.
“Quite a gentle run but actually getting faster and faster now as I get fitter.
“And the great thing about going for a run at the beginning of the day is that nothing can be worse for the rest of the day.
“If you really go in hard, if you really take some exercise at the beginning the rest of the day will be a breeze.
“So there are health reasons, but it also makes you feel much better.
“And that’s the number one thing, you actually feel more full of energy if you can get your weight down.
“And the other thing is that if you can get your weight down a bit and protect your health, you’ll also be protecting the NHS.”