SCOTTISH pupils are eating a diet of “grossly unhealthy” junk food which is on sale just yards from the school gates, according to a new study.

Four-fifths of snacks and takeaways regularly purchased by secondary school pupils contained too much fat, saturated fat or salt.

Only a single popular food contained one of the recommended five-a- day fruit and vegetables – lentil soup.

The survey of five Glasgow schools found that a single portion of some foods contained enough calories for a youngster’s entire daily needs.

The study, led by Dr Anne Ellaway, of the Medical Research Council’s Social and Public Health Sciences Unit at Glasgow University, backed a crackdown on fast food and other outlets.

“There is ample opportunity for school pupils to purchase oversized energy dense products that are high in fat and salt during their school lunchtime break,” it said.

“This study provide clear evidence regarding the adverse impacts on pupils’ health and wellbeing of leaving school at lunchtime to purchase off-site food and highlight the need for greater availability of healthy, tasty, low cost food in external outlets.

“The maintenance and promotion of strict nutritional standards in relation to school based food and drinks are unlikely to bear fruit when such grossly unhealthy options are available and promoted just beyond the school gate.”

In 2016, 65 per cent of adults aged 16 and over were overweight, including 29 per cent who were obese. Almost one-third (29 per cent) of children aged between two and 15 were at risk of being overweight or obese.

The number of secondary pupils taking school meals is declining and almost two-thirds buy their lunch outside the school grounds.

The study concentrated on five secondary schools. Pupils were followed by teams to observe their lunchtime habits.

Notes were taken of the fish and chip shops, kebab shops, convenience stores, newsagents, bakeries, mobile catering units, cafés, pizzerias, sandwich shops and supermarkets visited within a 10-minute walk.

The number of outlets in the vicinity ranged from five to 30.

“Observers noted a brisk exodus from the school grounds by pupils when the lunchtime bell rang,” the study said.

“Long queues of pupils quickly formed at popular outlets.”

The study found that 58 per cent of the most popular choices exceeded total fat recommendations and 42 per cent had too much salt.

Twenty two of the food items exceeded the recommended energy level for school lunch – 664 calories. The worst was a doner kebab and chips containing 1,314 calories per portion. A large lentil soup had just 120 calories.

The study, published in the journal BMC Public Health, recommended the use of “licensing and planning powers to limit the number and concentration of commercial outlets selling unhealthy food in local neighbourhoods and near schools”.

It added: “Public health action needs to take place across educational, commercial, and local authority boundaries as well as through engagement and awareness raising work with parents and pupils.”

Several councils did previously introduce a ban on snack vans close to schools.

But North Lanarkshire Council last year lost a court battle over its ban after a group of burger van owners argued it conflicted with their human rights and those of their customers. The ban was deemed unlawful at a civil hearing at Hamilton Sheriff Court.