Jebb, who is head of diet and population health at the Medical Research Council, said: "The old model of just selling people more calories isn't good enough. Food is a complex system and we will need a whole portfolio of interventions if we want to change behaviour, and we can only act in a coordinated manner. But how much intervention into people's personal lives is it reasonable to make?"
Children from deprived backgrounds are twice as likely to be obese as those further up the social scale, she pointed out. "Whose responsibility is that? People say 'the Government', but in peacetime it's hard for the Government to take a strong lead."
But she praised the latest Responsibility Deal pledge on fruit and vegetables, launched by the Department of Health on the same day, as showing "a diversity of effort by industry in response to this problem".
Supported by several large retailers, this will bring initiatives ranging from increased display space for fresh produce to promotions aimed at customers who do not currently buy fresh produce. Similar pledges have already yielded cuts in people's calorie and salt intakes, the Government has claimed.