Certainly, he sees a distinct change in the way he now lives: "it was pukka'd up, it was chirpy and cocky and life was great, but I didn't know enough about the realities of business and all the grown up stuff that revolves around a man," he tells me. "I was just loving life and partying and cooking."
He admits that he while he "may have made money" (his net worth is an estimated £150 million according to one Rich List), he's "also lost loads" (he won't tell me exactly how much - but he's down £90m since his peak in 2014).
What he calls the "30 to 40 year old bit" he does concede was exhausting: "I basically squirreled nothing away, I built no safety and I had a slightly weird view of the recession." He says he now has "lists of friends that I shouldn't have collaborated with - never mix business and pleasure".
But he is also proud of what he achieved, which is considerable by anyone's standard. Today, he has 48 restaurants in the UK alone and 19 books printed in 36 languages: "If you're 30 and you've got a talent you've got to smash it and that's what we did - we created 8500 jobs and we tried anything that would get anybody cooking. We put good heart and soul in it."
Today, as a father of five (his eldest is 15 and youngest, River, was born last August), the parties are presumably a bit far and few between. "It is a struggle with nappies all over the house and stair gates, we've got three sets of kids - we've got teenagers so that's revision, hormones, the whole thing. I'd give myself a 6 out of 10 as a dad to teenagers. I don't think I'm very good to be honest.
"And they're girls, which is really hard and they're not interested in much I've got to offer. And then the others are 6 and 8 and I'm pretty good at that. And then one is a baby and we're back to the beginning."
So, is that it on the baby-making front? "I think so, yes. I think at 42 you're pushing your luck. I haven't got any more room in the car, so we'd have to buy a bus. But Jools would love me to say 'never say never.' She'd tell me not to rule it out."
TOTAL DEVOTION TO JOOLS
His devotion to wife Jools (who he met aged 17 while on a double date with tv co-star Jimmy Doherty), is resolute; "she is quite a girl. I'm pretty much in awe of her; she's as amazing as a mum could get."
While much of their relationship is played out on social media (both Jamie and Jools are prolific Instagram users), anyone who spends time with them together can see the absolute devotion they have for one another which, given Jamie's work schedule, must be nothing short of challenging.
The key to their relationship is, according to Jamie, "keeping work really separate" from family life. "You probably know more about what I'm doing than she does," he says. "You've just got to make stuff work, although we definitely don't have enough time for just us."
WHY ANOTHER COOKBOOK?
So, with restaurants the world over and food tomes on nearly every bookshelf, why another? 5 Ingredients Quick & Easy Food is, unsurprisingly, all about making delicious, nutritious food using no more than five ingredients in one dish. "I have, over the years, done speed, money, time, and comfort and, weirdly, this book was a really obvious one that hadn't been done. I began writing and very quickly started getting blown away."
He is open about the challenges he has faced with dyslexia and feels he's "certainly not a beautiful writer like Nigel [Slater]," but it's this passion for healthy and enjoyable homemade food, which drives him to write and, more latterly, campaign.
Jamie has worked with four Prime Ministers since he started the School Dinners campaign, "when there were standards for dog food but not kids' food" and, naturally, our discussion moves to Theresa May's move to scrap free school lunches, which he is still furious about: "She's going to dig her heels in and now I'm just an irritation. She doesn't give a hoot and she doesn't care about kids' futures."
He reminisces about his work with David Cameron who he clearly enjoyed dealing with, though he credits George Osborne for putting through the sugar tax: "Apart from being absolutely right, it's a billion quid going into schools. Whatever you think of George, that was a moment."
JAMIE THE DO-GOODER
His passionate outbursts have led some to berate him as a lecturing do-gooder who has gone about his mission in a somewhat clumsy and naive way. He has been slammed for not understanding the challenges faced by the poor when criticising ready meals but it's hard not to see that his heart is in the right place.
But has he been as good about looking after his own health as he has the nation's? Getting older hasn't just been about an existential crisis, and there has been a notable physical impact, too. "My body probably does react differently now". He turned over his own healthy leaf when he hit 40, cutting out alcohol during the week and watching what he ate; "I'll go to the gym as many times as my diary allows but, eating-wise, I try and rattle out Everyday Superfoods from Monday to Thursday. Doing the right thing does involve quite a lot of thinking; making that easy for people is the holy grail."
So, no retirement plans just yet then? "I'm pretty clear I don't want it to be the same as the last ten years. Do I take my kids to school every day and retire? I'm not going to do that. I will still try to push boundaries and I want to be much more medical, educational and political, but in a really grown up way."
His new plan is to "employ the best cancer dietician in the country and give them a platform that will allow their work to flourish." While he has no personal history of cancer in his family, his hope is to work more closely with people on a one-to-one basis, in order to help them with individual nutritional needs, while doctors work alongside him to study their family history and medical health, advising on lifestyle and diet simultaneously. "If you start joining it (healthy eating) with technology, the possibilities are endless."
