More than a quarter of UK teenagers consume sports drinks designed for high intensity exercise while at the cinema, watching TV or gaming, a study has found.

Some 25 per cent of teens think sports drinks are healthy enough to be drunk anytime, despite health guidelines stating they should only be used during high intensity activity lasting more than an hour, according to research for the Natural Hydration Council (NHC).

More than a quarter of teenagers (28 per cent) thought sports drinks were healthy to drink when they were exercising for less than an hour and 27 per cent drank them while inactive at the movies or in front of the TV or computer.

Just 16 per cent of teenagers who drank sports drinks did so for the reason they were designed for, the poll found.

Nearly half of all teenagers surveyed (48 per cent) said they often felt thirsty and 40 per cent said they were not sure what their body needed to keep hydrated.

The European Food Safety Authority (EFSA) states sports drinks, which contain an average of 18g of sugar, are only effective for “active individuals performing endurance exercise”.

A draft report from the Scientific Advisory Committee on Nutrition (SACN) urged a reduction from the current recommendation of sugar as 10 per cent of dietary energy intake to 5 per cent.

This is the equivalent of 25 grams of sugar for women and 35 grams – or seven to eight teaspoonfuls – for men.

Professor Paul Gately, Professor of Exercise and Obesity at Leeds Metropolitan University and adviser to the NHC, said: “Sports drinks have a clear purpose for athletes participating in high intensity exercise – otherwise people are just consuming water, salt and on average 16 grams of sugar in each 500ml bottle.

“Teenagers often perceive these drinks to be more healthy than other soft drinks, when they really only have a purpose to help those who are being vigorously active.

“Knowing which drinks to choose for the amount of physical or recreational exercise you do is important.

“Drinking water will keep most people well hydrated.”