He appeared alongside Good Morning Britain with Piers Morgan, who later tweeted: “BREAKING: Labour’s deputy leader @tom_watson just revealed to @GMB that he’s lost 67lbs since August. Amazing!”
Twitter users responded positively, with one writing: “Must say you’re looking great @tomwatson – are you back to university days size?”
Another added: “Wow Tom Watson looks really trim these days. Well done to him”.
Last year Piers had his own weight loss bet with Lord Alan Sugar, which he then lost.
But how did the Labour MP lose the weight?
Writing in his newsletter last October, Tom said he had been on a diet.
“Did I tell you I’m on a diet? I know you’re not supposed to call them that anymore, to be on message they have to be a ‘lifestyle change’.”
In the same letter, he revealed he had been using a “nudge theory” technique to held him shed the pounds.
What is nudge theory for diet?
Nudge theory is a technique of rewarding “good” behaviour with rewards to encourage you to do it again.
Tom did this through buying himself small gifts, as he explained in his letter.
“Using rudimentary ‘nudge theory’ every time I reach a weight target, I treat myself to a gadget for the bike.
“It’s going well so I purchased a device for the handle bars that allows you to attach your iphone this week.”
Alexa Fears, 34, who works in marketing, has credited a special high fat keto diet with transforming her from a morbidly obese 23 stone to a slender size 12.
Estimating that she weighed around 23 stone, Alexa shopped in specialist shops. However, the keto diet, or ketogenic diet, which involves following a low carb regimen, helped her lose 10 stone.
Now Alexa is virtually unrecognisable, having shed 10 stone – five-and-a-half since September 2016 – and dropped seven dress sizes.