John, who has extended his contract by a year at Upton Park after agreeing a pay cut, is better known for his exploits on the golf course.
But it is stepping through the ropes rather than hacking his way round the fairway that has taken up more of his spare time recently.
While Trevor Sinclair is a fan of watching the fight game, and would have been watching Lennox at the weekend if he had not had a more pressing engagement to attend to, John has a more proactive approach to the sport, and reveals:
"I have had to do a lot more training on my own these days, to be honest, and I go boxing training twice a week down the local gym, and things like that.
"I have to work just to keep in there with a chance and to keep my fitness levels somewhere near the standard that is required, because the game has certainly moved on in terms of fitness.
"I do get in there and have a spar; it is good because as well as your upper body you are getting an all round work out and the lungs get worked really hard.
"It is a different type of fitness and it builds your character as well; it has certainly been good for me.
"A lot of my mates who I grew up with are finished now and it definitely for me a change of attitude and diet that keeps you in there fighting.
"In a lot of ways it builds your character to play; the game doesn't get any easier and there are certain times in games when it really is hard, and if you can dig deep and do a little bit extra, even at the age of 36 which is what I will be in September, it is just an added bonus.
"But in years gone by, if I had lived the sort of life I did eight or nine years ago, I would be struggling now."
John candidly admits that, had he continued leading an active social life, he would not be playing now, and explains:
"The culture in the English game was drinking, to be honest, and when I started out at Spurs it was a big one - lads would go out on Wednesday and Thursday and not bat an eyelid.
"It has all changed now, but it has had to; I'm not saying drinking has been knocked on the head completely, but you have to know when and where to drink.
"Saturday night was always a big night but now it is probably the worst time to drink, apparently, because your body needs to be refuelled.
"The eating has changed as well; when I first came we always used to have egg and bacon, and sausages and things, which we obviously don't have any more.
"Someone like John McCarthy is good because he gives you so many reasons why sometimes you feel tired, and how to get the best out of your body, there is so much about it now and I think all clubs have gone that way - it is a big business now.
"I think as you get older you change and I have got three boys now - that has altered me more than anything.
"You have to look to do the right things, especially as an athlete who is ageing, it had to be done.
"It has definitely put a few years on my career; I look at my old mate Paul Gascoigne, and I know he is still about, but I don't think the drink has helped him in his career - though I'm not saying it is purely down to that.
"Another factor is injuries and I don't think it has helped him; they say it causes a lot of injuries at times and also it is probably harder to get over them if you are living that sort of lifestyle.
"At the end of the day, his problems have been publicised so much he doesn't need me banging on to him - and he probably wouldn't listen to me anyway, he would probably laugh.
"You have to look after yourself; Glenn knew me years back with Paul Gascoigne and at the end of the day I was one of those that loved a drink and lived life to the full - but it had to change, and I have changed over the last five years.
"There were a couple of years when we were always out.
"More than ever you have to look after your body, and if you don't you are history, the way the game has come on."
"But at the end of the day, it is definitely a hard level now to play at the top, and the foreign players have brought it in more than anyone, and not many of them get involved in anything like that.
"They look after their bodies and have probably been a better example to the English players.
"It brought in a bit more professionalism, and a different culture; there have been a lot of foreign players at West Ham over the years and in general I would say they are professional."
John certainly enjoyed something of a renaissance last season, after barely getting a look in the season before, and he adds:
"I think it was something like 18 appearances and about nine starts, but at the end of the day it is about me playing.
"It is no good me signing and just saying 'I have got another year - happy days' because I want to play and get in there.
"That is the sort of character I am and to get so many outings last year at my age was a good thing for me and it always gave me something to strive for.
"The manager said he was impressed with the way my attitude has been and he feels that I can offer the lads something in training.
"Obviously when I get called to play I won't let anyone down, and Glenn sees that there is a position for me to be used - and that is why I am one of those he has kept."
And a final word on his boxing career?
"The old bugle hasn't gone yet, so I can ride a punch or two - I can hand them out as well!"