She said meals "out of home" were a major cause, with retailers selling high-calorie foods as "treats" which encouraged overconsumption.
"This is all about things like pizzas and ready-made sandwiches. We will need to set out guidelines and, I suspect, a series of calorie caps," she said.
New guidelines published last month recommended no more than 1600 calories a day for meals with two snacks of 100 calories each also permitted in a healthy diet.
A McDonald's Big Mac in New Zealand contains 485 calories.
The measures were described by the National Obesity Forum as a "panic measure to get the public to understand they are eating too much".
The most recent nationwide statistics, published last year, showed that some 63% of adults in England were too heavy, with 36% overweight and 27% registering as obese.
Rates of obesity were particularly high among older people and in deprived areas, with men more likely to be overweight or obese than women.
Meanwhile, a study at Oxford University found that Britons may also be drinking too much.
Current health guidelines recommend that men and women should not regularly drink more than two units of alcohol a day.
But the new study in the Journal of Public Health found that consuming more than one unit of alcohol a day is 'detrimental to cognitive performance', especially among older people.
One unit is equivalent to around a third of a pint of beer or half a glass of red wine, according to DrinkAware.
