A national programme to prevent people developing Type 2 diabetes is unlikely to have a major impact, research suggests.
The NHS Diabetes Prevention Programme started last year and will be rolled out across England by 2020, with up to 100,000 people being referred to it each year.
Those sent on the programme by their GP will get tailored, personalised help to reduce their risk of Type 2 diabetes. This includes lessons on healthy eating, help to lose weight and bespoke exercise programmes.
People are identified as being at risk of diabetes through two types of blood test or through an NHS health check.
But new research led by the University of Oxford throws doubt on such schemes, saying there is a lack of evidence that they help prevent diabetes.
In a new study published in the British Medical Journal (BMJ), experts examined 49 studies of screening tests for diabetes, including the two blood sugar tests. They also looked at 50 intervention trials, including lifestyle, diet and exercise interventions, or the use of the drug metformin, which is used to improve blood sugar control.
The researchers concluded that neither of the blood tests used to detect high blood sugar - as used by the NHS Diabetes Prevention Programme - were accurate enough for detecting people at high risk of diabetes while excluding those at low risk.
Lifestyle interventions led to a 36% reduction in the risk of Type 2 diabetes in a period up to six years, but this dropped to 20% after the trials ended.
The authors concluded: "As screening is inaccurate, many people will receive an incorrect diagnosis and be referred on for interventions while others will be falsely reassured and not offered the intervention. These findings suggest that 'screen and treat' policies alone are unlikely to have substantial impact on the worsening epidemic of Type 2 diabetes."
Figures published last year to help launch the NHS programme showed five million people in England are at high risk of developing Type 2 diabetes, which is linked to obesity and unhealthy lifestyles.
In most parts of the country, more than one in 10 adults are at risk of Type 2 diabetes and, in some regions, the risk is around one in seven, Public Health England (PHE) said.
Some 2.9 million people in England are already diagnosed with Type 2 diabetes, with obesity seen as a key driver.
Figures suggest that Type 2 diabetes already leads to 22,000 early deaths every year and costs the NHS around £8.8 billion.
Matt Fagg, programme director for the NHS Diabetes Prevention Programme, said: "Around five million people in this country are at risk of Type 2 Diabetes. The Healthier You: NHS Diabetes Prevention Programme is a key part of the solution and is based on a comprehensive collation of robust evidence.
"But diabetes prevention also needs to start even earlier - we're committed to reducing obesity and creating a more active culture so that we see fewer people at risk in the first place."