James Corden wants to lose weight to "be better" for his children and his family.
The Late Late Show host has signed up to front WW - who were formerly known as Weight Watchers - after "eating everything that's in the fridge" this Christmas.
Explaining his decision to join WW, he said: "I want to change the way that I live. I want to be better for my children and for my family. I've realised that every year for the past decade - probably even 15 years - on January the 1st I've told myself and anyone that would listen that I'm going on a diet, I'm going to lose a load of weight. I'm fed up with the way I look, I'm fed up with being unhealthy, this is the year I'm doing it.
"Because of that, over Christmas I've eaten everything that's in the fridge because in my head in January I'm starting this diet and it'll be a success. And as you can see it hasn't."
The 42-year-old television presenter and actor admits his weight has been "getting him down".
Speaking about how his weight makes him feel, he added: "It's starting to get me down in a way. I've never been able to stick to anything like that. I've spent a long time accepting that this is my body and that's it. But I really am sick and tired of just doing the same thing every year. I contacted the people at WW and I said: 'Look, can you help me with this? Why does this keep not working for me?'
"They told me that what I'm probably doing wrong is that I'm going on a diet and that is probably not the answer. They said: 'If you stick with our regime, which is more about wellness and health and feeling better rather than lose a load of weight this can absolutely work.'
"I don't want to wake up tired, or feel embarrassed when I'm chasing my son on the football field and out of breath after three minutes."