From the start of this term, the authority has introduced a "presumption" in eight of its secondaries that S1s will stay in over lunch break and eat school meals or packed lunches.
The policy is designed to encourage healthier eating habits by removing easy access to unhealthy food in nearby shops and fast-food outlets. Pupils are encouraged to participate in sports or cultural lunchtime activities to make staying in school a more attractive option.
Steven Purcell, leader of Glasgow City Council, said: "This initiative can help banish our city's poor health image. I know this isn't going to happen overnight, but it's another step in the right direction."
Scottish Government statistics show that the uptake of school lunches by primary children in Glasgow is one of the highest in Scotland at 59 per cent - it was one of the authorities to pilot free school meals for all P1-3 children - against a Scottish average of 48 per cent. The figure for secondary pupils is 30 per cent in Glasgow compared to a Scottish average of 39 per cent.
Gerry Lyons, headteacher of All Saints Secondary, said around 90 per cent of his S1 pupils were eating school or packed lunches. Of the 10 per cent not doing so, some were observing Ramadan, which involves fasting from dawn until sunset, and six were going home for lunch.
Staff were not taking the register at lunchtime to ensure the pupils were staying at school, but were carrying out spot-checks in the dining area and at the school gate, he said.
On Mondays and Wednesdays, S1 pupils can go to a "chill out zone" and on Fridays, a range of activities are offered by Culture and Sport Glasgow. S1s have a dedicated playground equipped with light balls, skipping ropes, bats and pogo sticks. On wet days, they will have access to the gyms and S6 pupils will run basketball games for them, in turn earning school sports leadership awards.
One of the biggest challenges was finding enough organised activities for 190 S1 pupils, Mr Lyons said.