The NHS should call on slimming clubs and leisure centres to help it fight obesity, say researchers.
Obesity is a major health problem
It follows a study in the British Medical Journal in which they expressed doubts about whether GPs and nurses can, by themselves, tackle the problem.
Their study of 44 general practices in England found training staff to fight obesity has little effect.
They said other strategies are urgently needed if Britain is to fight what has become a "major public health problem".
An estimated 30,000 people die prematurely from obesity-related conditions every year in the UK. One in five men and one in four women is now obese.
A recent study by the National Audit Office estimated the condition costs the NHS at least £500m a year and the wider economy more than £2bn a year in lost productivity.
The government published a national service framework for coronary heart disease three years ago. It includes targets for reducing obesity.
Since then a number of different training programmes have been set up to help general practice teams to work towards those targets.
Helen Moore and colleagues at the Centre for Research in Primary Care at the University of Leeds examined the effectiveness of one type of training programme.
They asked staff from 22 out of a total of 44 general practices in the north of England were asked to attend three 90 minute sessions. The practices were in Durham, Leeds, Newcastle and Scarborough.
The sessions were held at least one week apart but not more than two weeks apart.
Dieticians told doctors and nurses on the course about the latest scientific evidence on the management of obesity.
This included information on how to encourage patients to lose weight, what type of diets they could go on and what drugs are available.
"The training programme was realistic in terms of the type of training that might be delivered to primary care teams by NHS dieticians," the researchers said.
Doctors and staff from the other 22 practices received no training at all.
The researchers examined how teams from all of the practices fared in helping a total of 843 obese patients to lose weight.
One year on, there was no difference between those patients attending trained practices and those were team members did not receive training.
Just one in seven trained practices managed to hit their targets to reduce obesity.
The researchers found that in many cases doctors and nurses simply failed to discuss obesity properly with patients. Many failed to set a target weight or prescribe a diet or exercise programme.
They concluded staff may need more in-depth training. But they acknowledged that with other demands on their time, other strategies may be needed.
They suggested the NHS may consider looking to the private sector to help it fight obesity.
"Other strategies to manage obesity in primary care urgently need to be considered and evaluated.
"These might include motivated and dedicated obesity specialists placed at the level of the primary care trust, use of leisure services and use of the commercial weight loss sector," they said.