THERE is an irony in prime athletes being quizzed on their dietary habits by tubby journalists, but even in the throes of victory - such as the midweek Europa League triumph against Dinamo Zagreb - Celtic press conferences are starting to resemble episodes of TV weight loss show 'The Biggest Loser'.

Regardless of this week's controversy about salmonella being discovered in the Celtic Park catering, enquiries about the new diet and fitness testing regime at the club are often on the menu. There was certainly food for thought this week in the post-match offerings of Anthony Stokes and Kris Commons.

These are two men who often appear to display an almost telepathic understanding on the park - not least when they combined to produce the early goal which moved the Parkhead club joint top of their Europa League group - but on this subject there were differences of interpretation which said it all about the collective buy-in required under Ronny Deila's calorie crackdown. While the ferocity and efficiency of the pressing game the Parkhead side displayed in the opening half hour against Zagreb hinted at how formidable this team could yet become, the manner in which they tired left some thinking they may have bitten off more than they can chew.

Stokes is perhaps the case study par excellence when it comes to this Celtic squad. The Irishman, speaking more candidly than any player has yet on the subject, says he has lost five kilos since pre-season under the rigorous fortnightly testing regime implemented by the Norwegian. Moreover, with only one lone striker's role seemingly predestined for either John Guidetti or Stefan Scepovic when fit and available, he has uncomplainingly been shifted to the left side, using it as a base to put in a fine shift recently against St Mirren. Yet while Deila praised the Irish striker's attitude, last night the Norwegian said he was still only "70 per cent" of what he could be.

To what extent Deila is re-inventing the wheel is a moot point, but thanks to his fortnightly testing regime, Stokes certainly has more statistics at his disposal to back up his manager's decisions. "I think he just wants to eke five or ten per cent more from every player.

"Everyone is trying to cut down. He is very rigid on body fat and body weight. He wants everyone at their prime. I definitely have changed, I'm probably down five kilos since I came back for pre-season. I still probably have another couple of kilos to get to the weight that he wants, but I don't mind that. If I can get to my prime body weight that's only going to help me. It's one of the things I'm focusing on more than I have at any stage in my career."

Deila is nothing if not a hard task master. "Stokes has a very good attitude," said Deila. "But he's only 70% of what he can be fitness wise in my opinion. His skills are unbelievable - what he produced on Thursday night with Kris is high level. But there's a lot more to come."

The root of the difference of opinion, perhaps, is that Deila is more idealistic than the players themselves. He might not be able to buy the best players on the continent, but having spent time with Jurgen Klopp's Dortmund side, he sees no reason why they can't be as fit as any team in Europe.

"It's all about being true to ourselves," said Deila, who admits Celtic have been fortunate in their two Europa League matches to date. "You don't create that in a couple of months because it happens over time, but I think we are adapting more and more. If you look at the teams we have played in Europe - Legia, Maribor, Salzburg and Zagreb - they are all of a similar level and you can see that we are getting better results all the time."

Commons, of course, was another who made a telling contribution to his team on Thursday night, particularly as he continues to manage an injury to his gluteal muscle. His manager may talk a good game, but Commons, always more of a Neil Lennon supporter, isn't so sure that - at least when it comes to the pressing game utilised on Thursday night - things are so different after all.

"To be honest with you, it is no different than when Neil was in charge," said Commons. "His tactics were always to put teams under pressure, make them kick long, let them make mistakes - unless you are playing the likes of Barcelona, Real Madrid, in which case it doesn't matter how much pressure you put them under because they are so good they will probably pick you off. Then you park the bus. In my time with Neil it was always that sort of intensity."

While it may be different in away matches right now, the long-term aim is to press high up the pitch home and away, the same way Barcelona and Bayern Munich do. Thursday night gave the 30,000 or so Celtic fans who turned up at least a half-hour glimpse of Deila's high ideals. Today an eager Hamilton Academical side will turn up, hoping like Inverness Caledonian Thistle, Dundee and Motherwell before them this season, that it has all taken it a bit too much out of them.