A chemical used in make-up and self tanning lotions has been linked to obesity.

Scientists found that those who were exposed to phthalates, colourless man-made substances included in a variety of common consumer products, were more prone to weight gain.

And subjects with even 'modest' levels of the substance in their bloodstream were twice as likely to develop diabetes.

One billion tons of phthalates are produced worldwide each year and they have been widely used as gelling agents in cosmetics, cleaning products and to make plastic bottles for more than half a century.

But now mounting evidence suggests they could have a negative health impact, prompting the body to store more belly fat and become resistant to insulin as they disrupt the hormone balance.

Lead researcher Monica Lind, associate professor of environmental medicine at Uppsala University in Sweden, said: 'Those pollutants containing phthalates are making people obese and now we find they could get diabetes. These products need to be tested.

'Many are used in body products, like face creams, fake tan, make up and perfumes. Not only does the packaging contain them, but they are absorbed into the body and bloodstream through the skin.
'In perfume, we inhale the phthalates that are used to delay the scent and increase the lifetime of the perfume.'

Data from 1,000 people aged over 70 was looked at during the study and in total 119 had diabetes while 88 of them had a history of the condition.

After taking into account factors that are known to cause type 2 diabetes, including obesity, smoking and high cholesterol, they found people with higher levels of phthalates in their blood were more likely to develop insulin resistance.

It is thought that in men phthalates have an anti-testosterone capacity linked to weigh gain, while in women they disrupt the hormone balance similar to those that might occur during the menopause or at puberty.

It is unclear which products contain the chemicals, as in many countries don't require them to be listed as ingredients, but it is known that perfumes and hair products, such as hairspray and mousse, are the worst offenders.

A spokesperson from Campaign for Safe Cosmetics said: 'Phthalates are found in about 70 per cent of fragrance containing personal care products (that's everything from perfume and cologne to fragrance-containing shampoos and deodorants).

'They are not listed on labels because fragrance is considered a trade secret so companies don't have to disclose what's in it.'

Dr Paula Baillie-Hamilton, author of Stop the 21st Century Killing You and a researcher on human metabolism who has studied the connection between chemicals and obesity at the University of Stirling, is convinced that the abundance of chemical calories in our lives is the reason why so many people are getting fatter despite dieting and exercising more.

'It's a theory that was poo-pooed a decade ago but which has become a new field of medicine in itself,' says Dr Baillie-Hamilton.

In 2003 the European Union passed legislation banning some phthalates in cosmetics and has kept three phthalates out of toys since 1999.

Johanna Congleton, a senior scientist from the Environmental Working Group, a U.S. environmental organisation, said the study gives further reason for the cosmetics industry to ban the use of phthalates completely.

She said; 'The implications of this study enforce the notion that environmental chemicals can act as 'obesogens' and alter biological functions involved in fat metabolism, which can influence body weight.

'Avoiding exposure is a good precautionary measure, and consumer product manufacturers should phase out the use of these compounds.'

However Dr Iain Frame, Director of Research at Diabetes UK raised concerns over the recent study and the sample selected.

He said: 'This paper attempts to link the presence of phthalates in the bloodstream and the presence of Type 2 diabetes in an elderly population.

'It is a difficult area to research and this study was based on a relatively small number of white adults over 70 years old.

'It shows an association between some metabolites, which are breakdown products, and the presence of Type 2 diabetes, but does not show that their presence causes Type 2 diabetes.

'We would be concerned if the reporting of this study diluted the very simple and evidence-based message that limiting the amount of calories in your diet and being regularly physically active is the best way of maintaining a healthy weight and so reduce your risk of Type 2 diabetes.'

Following the publication of the findings in the journal Diabetes Care, Prof Lind added: 'Although our results need to be confirmed in more studies, they do support the hypothesis that certain environmental chemicals can contribute to the development of diabetes.

'Consumers should ask for labelling. As it is now It's impossible know which products contain the chemical. We should also ask for better regulation.

'There's lots of also lots of other health problems (asthma, allergy, obesity, reproduction problem etc) which has been shown to be linked to the phthalates.

'We now know enough to regulate these chemicals. In general all chemicals should be tested for safety before they go on the market not afterwards.'