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.