Labour's Clive Betts has defended going to Portugal with 15 fellow MPs last weekend on an all-expenses trip paid for by McDonald's.
McDonald's is one of the sponsors of Euro 2004
The MPs' decision to take part in a charity football match in the country at the expense of a fast food chain was criticised by public health experts.
The British Medical Association said the move was "seriously irresponsible".
But Mr Betts said if MPs had a "puritanical" attitude about food then people would ignore what they said.
McDonalds picked up the tab for flights, hotel rooms and hospitality during the trip.
The BMA denounced MPs' decision saying: "For Members of Parliament to allow their names to be linked to promote fast food is seriously irresponsible."
But Mr Betts told BBC Radio 4's PM programme that if MPs adopted this approach, "young people are not going to take any notice of us, they're going to say it's those puritanical MPs lecturing us again".
He agreed that McDonald's had issues to address in relation to the content of its food but praised its community football scheme.
That had recruited four thousand coaches in some of the most deprived areas of the country, he argued.
"I think if McDonald's feel they can make a contribution towards getting more young people involved in sport and exercise, then let's give them credit for that," he said.
Last month, a Commons health committee warned fast food advertising had to be reduced in order to tackle the obesity "timebomb" threatening life expectancy.
Its report called for measures such as cookery lessons and a voluntary ban by the food industry on TV junk food ads.
Newspaper reports claimed the four-day trip by the Westminster Parliamentary Football Club cost £20,000.
It included watching England's game with France on Sunday and playing a charity match with their Portuguese counterparts.
A McDonald's spokesman declined to say how much the trip cost but said it had arranged the match as one of the sponsors of Euro 2004.
He said the company promoted a "balanced diet and lifestyle" and had a tradition of encouraging sport.
He said: "McDonald's Community Football Programme, of which we are very proud, will recruit and train 10,000 new community football coaches by 2006, encouraging and supporting the development of grassroots football."
The restaurant chain's menu had been changed to make it more healthy, he added.