Chancellor George Osbourne has taken up the 5-2 diet in order to shed a few pounds.
The 42-year-old is understood to have imposed austerity measures on his food intake as part of an image makeover.
Being on the diet means he has to fast on two days of the week, not consuming more than 600 calories.
On the other five days he can eat whatever he likes.
Aides have reportedly voiced hopes a slimmed-down image will boost his chances of succeeding David Cameron as Prime Minister.
A Government source told the Daily Mail: “George is on the 5-2 diet. Given the job he’s doing turning around the health of the economy, it’s unsurprising that he’s keeping himself in shape as well.”
Although the diet means watching his calorie intake on fast days, it does not preclude indulgences on the other days such as burgers, which he is known to enjoy.
The chancellor has also been pictured running around St James’s Park, across the road from the Treasury.