Medical experts claim that West Midlands tap water can make people FAT and could be fuelling rising obesity levels.
For the past 40 years, fluoride has been pumped into the region's tap water to help keep teeth healthy.
But now a top doctor claims that the toxin can cause worrying health side-effects including hypothyroidism, a medical dis-order affecting the thyroid gland which controls weight gain.
And he believes that children may be particularly susceptible to obesity if their mums drank fluoridated water while pregnant.
Last year, the West Midlands topped the UK 'fat list' with a shocking 22.5 per cent of its population classed clinically obese.
Dr Barry Durrant-Peatfield said: "There is no doubt that fluoride is enzyme disruptive and one thing it affects is thyroid hormones.
"As a result of this disruption, people can finish up with partial under-activity of the thyroid gland.
"Thyroid problems are becoming more common, particularly in Birmingham, and one of the reasons is because of fluoride in the water."
Dr Durrant-Peatfield explained that thyroid hormones rely on iodine, which is in the same group of four elements as fluorine. He said fluorine can displace iodine in the body, which can lead to problems with the thyroid gland.
"Children can be particularly affected if their mother was short of iodine during pregnancy," he said.
Dr Durrant-Peatfield's sensational claims have been backed by other medical experts, including Dr Diane Phillips, who only began suffering with thyroid problems after moving to the West Midlands.
So far only the West Midlands and areas in Tyne and Wear have fluoridated water, but a new government bill could see it rolled out to other areas of the country.
Sue King, of the Fluoride Exposure Network, said: "No checks on general health have been carried out in the fluoridated areas of the West Midlands, yet fluoride must have an effect on soft tissues.
"That is why it's so important to make sure that fluoride is removed from the water supplies because we are already getting it from so many sources, including toothpaste, fertilisers and air pollution."
Paul Castle, of Birmingham's Health Services, said: "There is no evidence of any link between water fluoridation and thyroid problems.
"Four years ago, independent research at the University of York concluded that further research on fluoride and thyroid should be regarded as low priority."
