A sweetener used in chocolate, cakes and fizzy drinks is the deadliest sugar, scientists warn.

Fructose, commonly used in the food industry, becomes damaging when artificially added to other food and drinks.

It is neutralised when present in fruit and vegetables - but turns rogue when imported into other products.

And experts say this raises the risk of obesity, diabetes, heart disease and stroke in the process.

Unhealthy: The fructose becomes bad for the body when imported into fizzy drinks, cakes and sweets, which are heavily consumed in the UK

Scientists at the University of Barcelona conducted a specialised study on rats using two different types of simple sugar.

They found that those given fructose water put on more weight than those given water infused with glucose - the body's natural blood sugar and preferred energy source.

The results, published in the American Journal of Physiology Heart and Circulatory Physiology, noted the former suffered more damaging effects on the metabolism and vascular system, not to mention a fatty liver and greater likelihood of obesity.

They also showed evidence of damaged metabolism and vascular system.

The findings are the latest in a long line of studies to highlight the damaging effects of fizzy drinks, cakes, biscuits and sweets.

Study author Professor Marta Alegret said: 'It is not shocking to discover the effects of fructose are seen in other similar sugars.

Sweet risk: Scientists at the University of Barcelona conducted a specialised study on rats using two different types of simple sugar

WHAT'S THE IDEAL DAILY SUGAR INTAKE? The government recommends that free or added sugars shouldn't make up more than 5 per cent of the energy (calories) you get from food and drink each day. That's a maximum of 30g of added sugar a day for adults, which is roughly seven sugar cubes. Children should have less – no more than 19g a day for children aged 4 to 6 years old (5 sugar cubes), and no more than 24g (6 sugar cubes) for children aged 7 to 10 years old. Added sugars are found in foods such as sweets, cakes, biscuits, chocolate, and some fizzy drinks and juice drinks – these are the sugary foods we should cut down on. Source: NHS Advertisement

'They show there are factors other than calorie intake, that can be associated with body weight gain.

'Weight gain in the liver seen in rats treated with fructose, not glucose, could affect body weight.'

The news comes shortly after it was revealed that chocolate manufacturers will reduce their products by 20 per cent in line with Government plans to combat child obesity.

Mars, Nestlé and Mondelez, which owns Cadbury, are said to be making their products smaller in a bid to stop them from being highlighted in a new report by Public Health England (PHE).

Several companies are reportedly reformulating their high-sugar products with artificial sweeteners to appease the Government, but some chocolate makers are concerned about changing the ingredients due to 'difficulties' that could be encountered.