The government should continue to refer people onto weight loss programmes, a new report suggests.
Figures from a Slimming World study over five years followed nearly 35,000 people on a 12-week course.
More than two thirds completed the course and each lost around a stone during that period.
However, some health groups have criticised the government for using private weight loss organisations.
Over the last decade the government has formed partnerships with private firms to try to curb worrying obesity levels.
It's estimated the government spends more than £4m a year tackling obesity.
The Department of Health says it will be looking into the way it tackles obesity over the next few months.
However, ministers insist slimming groups help people with motivation and are cost effective.
Dozens of NHS trusts across the UK recommend people join slimming clubs to help them achieve a healthy lifestyle.
Someone with a weight problem can be referred onto groups such as Slimming World and in most cases the NHS will pay for membership to get them started.
Twelve weeks on a Slimming World programme costs the NHS around £50 per person, half of what it would cost for weight loss medication such as diet pills.
However, some charities say they are only a short term solution.
Tam Fry from the National Obesity Forum (NOF) is concerned they are 'quick fixes' and not addressing the real problem.
He said: "The government has got to come up with a solution to stop people getting fat in the first place.
"It's relying too much on companies like Slimming World and Weight Watchers to do their job for them and it would be far better to put money into real prevention measures."
Beat, the UK's biggest Eating Disorder Charity, also supports the NOF's argument.
'Push I needed'
Chief Executive Susan Ringwood said: "Most people regain the weight they lose within two years, and many gain more than they first lost.
"Quick fixes that don't work just add to someone's sense of failure and can lead to the downward spiral of helplessness that can lead to much more serious mental health issues."
Twenty-two-year-old Debbie Rugg from Somerset has dropped from a size 20 to a size 12 since she was referred by her doctor to Slimming World last Summer.
She was diagnosed as clinically obese and had spent time in hospital after doctors feared her weight was having a deteriorating effect on her health.
She said: "At my heaviest, I was 15 stone and decided to do something about it after a breast cancer scare and lumps appearing on my body.
"I was given 12 weeks' worth of free vouchers and in the last ten months I've lost two and a half stone.
"Without being advised to join the programme and having my initial membership paid for, it wouldn't have given me the push I needed to get down to a healthy size."
Weight loss alternatives
However, the Slimming World study did show a third of people dropped out before completing their 12-week course, with critics suggesting more improvements are needed when it comes to long term weight loss plans.
Recent results from a weight loss scheme in Kent showed high drop-out rates and disappointing weight loss results overall.
Hundreds of people were given a cash reward, ranging between £70 and £425, depending on how much weight they lost during set target periods.
However two thirds of people on the 'Pounds for Pounds' programme didn't lose a clinically significant amount of weight and many dropped out before their course was over.
There are other weight loss treatments available on the NHS such as diet pills.
Last year the NHS spent nearly £37m on anti-obesity drugs. Other treatments include working with dieticians and psychologists.
In the most extreme cases, some people may choose weight loss surgery, such as gastric band operations.
Latest figures show there are more than 4,000 weight loss surgery procedures, done on the NHS every year - each operation costs anything between £5,000 and £14,000.