Weight loss surgery - otherwise known as bariatric surgery - is too often being seen as a "quick fix" to solving obesity problems, research suggests.
A new report found that many patients undergo operations without properly assessing of the risks the procedure poses to them.
More attention should be paid to pre-surgery counselling, the authors said.
The report, conducted by the National Confidential Enquiry into Patient Outcome and Death (Ncepod), examined the care given to 381 patients who were treated both privately and on the NHS.
The authors said that just a third of patients had received psychological counselling prior to referral for surgery.
And 24% of consent forms did not contain appropriate information. They also found that 32% of patients did not receive adequate follow-up after surgery.
And nearly a fifth of patients had to be readmitted to hospital, with some people needing further surgery, the researchers said.
The number of bariatric weight loss procedures - such as a gastric bypass or the fitting of gastric bands or balloons - rose by 70% between 2008 and 2010, Ncepod said. Between 2008 and 2009 there were 4,200 surgeries in England, this soared to 7,200 between 2009 and 2010.
"Bariatric surgery is a radical procedure with considerable risks, as well as benefits," said the report co-author and Ncepod clinical co-ordinator in surgery Ian Martin.
"It shouldn't be undertaken without providing full information and support to patients. But, when we reviewed cases we found examples of inadequate processes from start to finish - even the basics, such as giving patients dietary advice and education before decisions to operate are taken, were sometimes lacking."
Mr Martin also raised concerns about poor consent procedures and lack of psychological counselling prior to treatment, adding: "Consent often happens on the day the patient is admitted for surgery.
"This means there is no time for patients to reflect on their choices and have the opportunity to ask further questions about the risks and benefits of surgery before committing themselves to an operation."
The report authors said there should be a greater emphasis on psychological assessment before surgery. They also said there should be a two-stage consent process - so patients have time to weigh up the benefits and the risks.
But separate research published today states that if obese patients undergo bariatric surgery they can quickly reduce risk factors for heart disease and stroke.
The research, published in the journal Heart, says the impact of such surgery is greater and faster than drug treatments for weight management or diabetes and in some cases, could be life-saving.
President of the Royal College of Surgeons, Professor Norman Williams, said: "Bariatric surgery is not a quick fix. It has been proven to be an incredibly successful and cost-effective treatment for morbid obesity and the many serious conditions associated with it.
"New clinical guidelines aimed at improving the safe and effective provision of weight loss and metabolic surgery in the UK were issued earlier this year by professional bodies who specialise in weight-loss surgery, such as the British Obesity and Metabolic Surgery Society.
"Recommendations include a rigorous pre-operative multidisciplinary assessment involving surgeons, dieticians and psychologists.
"We will continue to work together with other health professionals in this area of surgery to ensure high standards of care and patient safety are maintained."
Robert Houtman, director of the Obesity Management Association, said: "Bariatric surgery does have a role to play in obesity management, but we should explore every other option before we resort to surgery.
"As the Ncepod report shows, surgery is too often seen as a quick fix, without patients being given full information about the risks, or alternatives.
"Obesity is a complex condition and, without accompanying behavioural and emotional support, the weight can pile back on and patients require further treatment. This is draining public funds, which are already reaching breaking point."
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