GPs should send patients who are at risk of developing type 2 diabetes to Weight Watchers, a new study suggests.
Patients with so-called pre-diabetes - where their blood sugar levels are above the normal range, but not high enough to be diagnosed as having the condition - could benefit from being referred to the weight management programme, experts found.
Researchers found "considerable reductions" in diabetes risk as well as an average weight loss of 10kg (22lbs) after a year.
The new study, published in BMJ Open Diabetes Research and Care, saw participants recruited through 14 GP practices in the London Borough of Bromley.
Patients with a body mass index score (BMI) of over 30 - signifying that they are clinically obese - who had non-diabetic hyperglycemia, or high blood sugar, were invited to take part.
They were offered a book in for a diabetes prevention programme with Weight Watchers which included a 90 minute "activation session" followed by 48 weekly group meetings.
Of the 117 patients who took part in the study, 38% had returned to normal blood sugar levels after a year.
A further 15% had reduced their risk of type 2 diabetes by reducing their blood glucose.
Just 3% had gone on to develop the condition.
At 12 months, 54% of patients achieved a greater than a 7% reduction in body weight, the researchers from Weight Watchers, the University of Westminster and Bromley Council found.
The mean weight loss was 10kg (22lbs).
The authors concluded: "A UK primary care referral route was successful in referring patients to a diabetes prevention program and that partnering with a commercial weight management diabetes prevention program translated into considerable reductions in diabetes risk."
They wrote that type 2 diabetes is a "significant public health challenge".
About nine in 10 people with diabetes have type 2 diabetes - which is linked to an unhealthy lifestyle.
Since 1996, the number of people diagnosed with diabetes in the UK has increased from 1.4 to 2.9 million. And by 2025 it is estimated that it will affect around one in every seven adults - around five million people.
Lead author Carolyn Piper, public health manager for the London Borough of Bromley, said: "A new diagnosis of type 2 diabetes is made every two minutes in the UK with the risk of developing the disease significantly influenced by our lifestyles. It's within our power to reverse the ever increasing tide of type 2 diabetes with the right education and support."
Co-author Zoe Griffiths, head of programme and public health at Weight Watchers UK, added: "We'd welcome the opportunity to work with Public Health England as part of the Healthier You: NHS Diabetes Prevention Programme rollout.
"Close to 80% of eligible patients who were offered the Weight Watchers diabetes prevention programme engaged, illustrating the significant scale that could be achieved by working together."
Commenting on the study, Emily Burns, interim head of research communications at Diabetes UK, said: "It's really important we help people lower their risk of type 2 diabetes.
"We know that diabetes prevention programmes, which support people to make lifestyle changes, can work. But more research is needed to work out how to apply this in a real world setting and make the risk of type 2 diabetes as low as possible for everyone."
Commenting on the study, Professor Helen Stokes-Lampard, chairwoman of the Royal College of General Practitioners, said: "Type 2 diabetes is a serious and potentially debilitating condition for patients, and it costs the NHS a huge amount of money every year, so the college welcomes any scheme that can prevent, or delay, its onset.
"Losing weight through a combination of responsible dieting and appropriate physical activity is one of the best things people can do to avoid developing, or lessen the impact of type 2 diabetes.
"But we know that many patients struggle to lose weight, and that the type of long-term behaviour change necessary can be hard to inspire.
"The findings that GP referrals to weight management programmes appear to have prevented a third of patients from developing type 2 diabetes are both positive and encouraging, and are certainly something for commissioners to consider.
"However, organised weight management programmes won't work for everyone so GPs and our teams will continue to play a pivotal role in managing the vast amount of diabetes care in the community, advising patients about lifestyle changes that can improve their health, so we must ensure that general practice has the investment it needs, and the appropriate number of GPs and nursing colleagues, to do this properly."