Obesity increases the risk of conditions such as cancer and diabetes
The number of people in England having obesity surgery has risen by 40% in the last year, figures show.
The NHS Information Centre statistics revealed there were 2,724 operations, including stomach stapling and gastric bypasses to reduce stomach size.
Overall, hospital admissions in 2007-8 caused directly by obesity topped 5,000 once strokes and heart problems were included - a 30% rise.
One in four adults are obese, but only the most severe qualify for surgery.
However, hospitals have reported they are struggling to cope with demands from even the most obese.
Professor Philip James, of the International Association for the Study of Obesity, said: "The number of people being treated by hospitals for obesity-related problems are just a small fraction of those that are eligible.
"The NHS just does not have the capacity and staff trained to deal with this."
Obesity has risen dramatically since the early 1990s.
In 1993, 16% of women and 13% of men were classed as obese, but by 2007 the figure stood at 24% for both.
Figures for children have also risen and now stand at just under a fifth.
The rising rates have prompted the government to launch a TV advertising campaign this year warning people about the risk of obesity and the links to cancer, diabetes and heart disease.
The three-year initiative follows a Foresight report, published last year, which warned the government must act to stop Britain "sleepwalking" into a crisis.
The report, which was the largest UK study into obesity, backed by the government and compiled by 250 experts, said excess weight had become the norm in our "obesogenic" society.
The NHS Information Centre also revealed that the number of drugs prescribed to treat obesity rose by 16% to 1.23m.
Public health minister Dawn Primarolo said said obesity was the "biggest health challenge" facing the country.
She said through the obesity campaign, the government was kick-starting a lifestyle revolution.
But she added: "Guidance on obesity recommends that drugs and surgery should always be a last resort - a better diet and more exercise should be tried first."
Shadow health secretary Andrew Lansley said more action was required from government.
"Too few people are aware of the recommended diet and exercise levels and too few have access to the information or support needed."