Woodford appeared alongside Shahriar Coupal, director of the Committees of Advertising Practice, and three figures advocating new regulations: Dr Emma Boyland of the University of Liverpool; Professor Russell Viner from the Obesity Health Alliance; and Dan Parker, former marketer and chief executive of Living Loud, a collective of health, digital and creative professionals working to promote healthy living.
The hearing follows last week’s session, when celebrity chefs Jamie Oliver and Hugh Fearnley-Whittingstall appeared before the committee to argue for government action.
Woodford argued that the UK already had some of the world’s toughest regulations on advertising HFSS products to children, and that evidence suggested and further regulations would have a minimal impact.
HFSS advertising was banned in all children’s media last year, bringing digital, outdoor and print into line with TV, where they have been banned during children’s programming since 2007.
But earlier this year, MPs made a call for the ads to be banned in all TV programming before the 9pm watershed – which would cover popular family primetime shows like Britain’s Got Talent and The X Factor.
Questioning Woodford, Conservative MP Jonny Mercer said: "When you watch one of these programmes [such as Britain’s Got Talent], you get belt-fed junk food adverts. Are you saying that’s not really the case?"
Woodford replied: "Yes, you’re seeing HFSS advertising, but other food advertising as well.
"Jamie said last week they’ll see an entire movie’s worth of HFSS advertising – they’ll probably see two movies worth of bank advertising. Does that make a difference to their [children’s] preference of bank? It’s designed not to appeal to them. They’re watching with the family, and actually it’s about parental choice."
Woodford and Coupal both told MPs that while advertising had an impact on people’s preferences, evidence showed it only had a very small impact on dietary behaviour.
And while obesity rates have continued to grow, exposure to advertising has actually been declining, Woodford said, adding: "That would suggest the other factors have been more important."
But Boyland said the claim about the modest impact of advertising on diet came from "now probably discredited data from the US from the 1980s", and that more recent evidence suggested the impact was much more pronounced.
"Even a single acute exposure to food advertising will increase children’s food intake by around 30-50 calories," she said. "48-71 additional calories every day is all that’s needed to generate weight gain.
"It’s very difficult to isolate the effect of food marketing on diet and obesity," she added. "But we know that advertising affects what children want to eat and changes purchasing behaviour."
As with efforts to cut tobacco use, advertising changes had to be considered as part of a package, Boyland argued: "Banning tobacco advertising didn't fix the smoking problem overnight, but it was one of a number of measures that changed the environment and what’s acceptable. This is one step towards changing the food environment."