Smoking shisha 'significantly increases' the risk of users developing diabetes and obesity, a new study has revealed for the first time.

Research carried out by the Brighton and Sussex Medical School (BSMS) found that smokers were more likely to gain weight and develop type 2 diabetes in comparison to non-smokers.

In the largest study to explore the adverse effects of hookah smoking, the participants baseline characteristics were measured against their biochemical results which were observed through blood tests.

Out of the 9,840 participants involved, 6,742 were non-smokers, 976 were ex-smokers, 864 were cigarette smokers, 1,067 were hookah smokers and 41 were both cigarette and hookah smokers.

Obesity, metabolic syndrome, diabetes and dyslipidemia were all positively associated with hookah smoking while negatively associated with cigarette smoking.

The research has cast doubt on the widespread belief that smoking hookah is less toxic because it involves an apparatus designed to purify tobacco smoke by passing it through water.

Professor Gordon Ferns, Head of the Department of Medical Education at BSMS, who led the study, said, "A single session of hookah smoking may be equivalent to more than a packet of cigarettes, and the inhaled toxic compounds may be even greater.

"It is unclear why hookah smoking is associated with obesity and diabetes.

"It is possible that the toxins in the smoke stimulate an inflammatory response that causes tissues to become resistant to the effects of the hormone insulin, that regulates glucose in the blood. However, it is also possible that hookah smoking is associated with other social behaviours that lead to weight gain."

As cigarette sales have steadily been falling for decades, people are increasingly turning to 'healthier' alternatives like e-cigarettes, vaping and hookah smoking.

However, while a cigarette is finished in an average of 20 puffs, shisha smokers can be exposed to greater volumes of tar heavy metals and other carcinogenic chemicals over a longer period of time.

The practice now accounts for around half of all the smoking that teenagers do, according to a British Medical Journal study published earlier this year.

Prof Ferns added: "There is now good evidence that hookah smoking is not harmless. The risks of hookah smoking with respect to some types of cancer is well established, and the evidence for an association with cardiovascular disease is growing.

"From a health policy perspective, it would be important for the public to recognise the risks of hookah smoking. The use of flavoured tobaccos may be particularly attractive to young people. Hookah smoking should be treated no differently from cigarette smoking."