If you love tucking into burgers and pizzas it's not just the takeaway that's bad for you - even the packaging can damage your health.
People who eat a lot of fast food are exposed to up to 40 per cent higher levels of potentially harmful chemicals, according to new research.
The study showed that fast food lovers are at greater risk from phthalates - a group of chemicals used to soften and increase the flexibility of plastic and vinyl - often found in packaging.
Phthalates have been banned from children's toys and products such as teething rings and soft books because of their potential toxic effects.
The chemicals are known to disrupt hormones and have been implicated in several illnesses and conditions including asthma to autism.
The new study, published in the journal Environmental Health Perspectives, is one of the first to look at fast-food consumption and exposure to phthalates.
Lead author, Assistant Professor Ami Zota, of Milken Institute School of Public Health in the United States, said: "People who ate the most fast food had phthalate levels that were as much as 40 per cent higher.
"Our findings raise concerns because phthalates have been linked to a number of serious health problems in children and adults."
Phthalates belong to a class of industrial chemicals used to make food packaging materials, tubing for dairy products, and other items used in the production of fast food.
Previous research suggests the chemicals can leach out of plastic food packaging and can contaminate highly processed food.
Doctor Zota and her colleagues looked at figures from 8,877 participants who had answered detailed questions about their diet in the past 24 hours, including consumption of fast food.
The participants also provided researchers with a urinary sample that could be tested for the breakdown products of two specific phthalates: DEHP and DiNP.
The researchers found that the more fast food participants in the study ate, the higher their exposure to phthalates.
People in the study with the highest consumption of fast food had 23.8 per cent higher levels of the breakdown product for DEHP in their urine sample.
And the same fast food lovers had nearly 40 per cent higher levels of DiNP metabolites in their urine, compared to people who ate no fast food in the 24 hours before testing.
The researchers also discovered that grain and meat items were the most significant contributors to phthalate exposure.
Dr Zota says the grain category contained a wide variety of items including bread, cake, pizza, burritos, rice dishes and noodles.
She said other studies have also identified grains as an important source of exposure to the potentially harmful chemicals.
The researchers also looked for exposure to another chemical found in plastic food packaging: Bisphenol A, or BPA.
It is believed exposure to BPA can lead to health and behaviour problems, especially for young children.
The study found no association between total fast food intake and BPA.
But Dr Zota and her colleagues found that people who ate fast food meat products had higher levels of BPA than people who didn't eat fast food.
This study fits into a bigger field of ongoing research showing that phthalates are in a wide variety of personal products, toys, perfume and even food.
Dr Zota said DEHP and DiNP are two phthalates still in use despite concerns that they leach out of products and get into the human body.
Studies have suggested they can damage the reproductive system and they may lead to infertility.
Dr Zota said large studies that might conclusively link phthalates in fast food and health problems could take years to conduct.
But she added: "People concerned about this issue can't go wrong by eating more fruits and vegetables and less fast food.
"A diet filled with whole foods offers a variety of health benefits that go far beyond the question of phthalates."