Parents with children at government schools will be urged to follow strict nutritional rules when packing lunches from September, under guidelines being drawn up by the Ministry of Education.
If they include soft drinks, crisps and certain sweets, they will be sent a letter telling them to replace them with fruit and vegetables.
The guidelines are part of a bid to tackle the growing childhood obesity problem and will match new requirements for school canteens.
Schools will also increase the time spent on physical education (PE).
The rules, which have yet to be finalised, replace a patchwork system where each school district writes its own regulations.
"Some will allow a bag of chips and others will not," said Aisha Al Siri, director of the ministry's school health department. "This made it difficult to monitor and regulate students' food intake."
Each district will be monitored by municipal and ministry officials. Last year, the ministry ordered schools to devote more time to PE - from twice a week to three times for primaries, and from once a week to twice for secondaries.
Mohamed Ali Mohamed, senior physical-education supervisor at the ministry, said it wanted to increase the requirement to three times a week across the board, but was stymied by a lack of time and staff.
Schools say more support from parents would help. "Parents who don't want their daughter to practise PE will often get a note excusing her from the class," said Mr Mohamed. "This is wrong. They do not realise the harm this could have on their child's health."
Dr Qazi Ahmed, a practitioner at Sheikh Khalifa Medical City, said this was very common. "Parents, especially those of children who have asthma, often come in looking for an excuse certificate," he said. "But we usually don't provide them - we advise them of the activities their children can safely participate in. In the case of asthma, for example, they can participate in almost all sports."
* Manal Ismail