Healthy and sustainable food must be promoted at the 2012 Olympic Games, according to a new report.
London 2012 recently launched a sustainability plan
The Soil Association (SA) said the benefits of local, seasonal and organic food could be showcased while imported food should meet Fairtrade standards.
Peter Melchatt from the SA said in the face of the current obesity crisis organisers "must promote healthy as well as sustainable food".
London 2012 said it was committed to a "sustainable food strategy".
The report by the Soil Association, the new economics foundation (nef) and the food and farming alliance Sustain, also noted that the Games could help promote sustainable fish consumption.
It called on 2012 sponsors Coca-Cola and McDonald's to serve 75% unprocessed, 50% locally sourced and 30% organic food and drink.
The Soil Association's Peter Melchett said: "If London is going to be the greenest Games ever, they have to tackle the 30% of our personal carbon footprint which comes from food.
"And if the Olympics want to avoid looking silly in the face of the obesity crisis now affecting most of the world, they must promote healthy as well as sustainable food."
The relationship between physical fitness and healthy food should also be highlighted at the event, the report said.
A London 2012 spokesperson said: "We have recently launched our sustainability plan which includes a commitment to developing a sustainable food strategy for the Olympic and Paralympic Games."
He said the report did not take into account the scale and practicalities of catering during the Games and did not cover all the areas of sustainability which need to be addressed.
"We do support the broad principles of local sourcing, minimum packaging, maximum recycling and working with our partners to promote sustainable and varied food during the Games," he added.