Adam, best known for his role as Ian Beale in the ITV soap, appeared on The One Show with his son Sam to talk about running the London Marathon together and wowed viewers with his svelte physique.
The actors face looked visibly slimmer as he chatted with hosts Matt Baker and Angela Scanlon, explaining that he has been trying a low carb diet to prepare for the 26.2 mile run on Sunday.
Image: BBC/ The One Show
Fans couldn't believe how much slimmer the 48-year-old looked, having lost weight whilst training for the marathon. Viewers at home tweeted using the show's hashtag, commenting on how good the dad-of-two looked during his interview.
One social media user said: 'Adam looking a lot slimmer! #TheOneShow'.
A second commented: 'B****y hell, Adam Woodyatt looks like a completely different bloke compared to Ian #skinny #theoneshow.'
Another Twitter used agreed: 'Omg Adam Woodyatt has lost weight!! #TheOneShow'.
Some watchers even thought Adam's transformation so significant they wondered how it would tie in with his role in the soap, asking 'Adam Woodyatt on #theoneshow has lost TONS of weight. How far ahead is EastEnders filmed?!'.
Adam and 19-year-old son Sam will be running the marathon and raising money for The Air Ambulance Service - an especially impressive achievement for the teenager, who was previously hit by a car whilst crossing the road and needed to be airlifted to hospital.
The car accident left Sam in a coma and wheelchair bound for some time, but he's now fit and healthy and will be running alongside his dad.
Adam in May 2016 attending the House of Fraser British Academy Television Awards.
'I've not trained with as much frequency and mileage as I'd have liked to, but despite that I do feel mentally and physically ready which is good,' the teenager wrote on his fundraising page for the big day.
'I'm declaring it here that I'm going to try to never slow to a walk at any point, so hold me to it and yell at me if I do (unless my pelvis falls apart or some other sort of crippling injury happens, in which case help me out and then yell at me.)'