Diana Wright rejected a call from the Royal Society for Public Health for the practice to be banned, saying it wouldn't change "the underlying issues" prompting kids to order takeaways in the first place, such as a lack of education or being poorly fed.
The RSPH, along with the Youth Health Movement and Slimming World, surveyed more than 570 teenagers on the childhood obesity epidemic.
They were asked about their own habits as well as potential solutions to the problem.
The report comes ahead of the Government's childhood obesity strategy which is expected to be published in the summer.
The RSPH study found:
Half of teens said fast food firms should be banned from delivering to schools
25% said they had ordered fast food to schhol in the past
Almost four in five believe supermarkets should offer free fruit and vegetables to children to snack on while shopping with their parents.
The majority believe that soft drink contents should display the equivalent number of teaspoons of sugar on the packaging.
82% think food manufacturers are misleading people when they provide fat, salt and sugar for single servings rather than for the entire product.
Speaking on Premier's News Hour Diana Wright said: "It's a challenge to the schools to do something more for young people, for children.
"I see young people come to see me because, actually, they're not able to eat what they need to eat when they need to eat it.
"The worry I have about it being banned is that the actual underlying issues won't be resolved.
"It just says: 'do not do this' rather than saying: 'why do you need this food - what is it we can do to help you'?"
Listen to Premier's Hannah Tooley speaking to Diana Wright on the News Hour:
