A red-brick surgery in the seaside resort of Southport in the north-west of England is on the frontline of one of the biggest questions facing the NHS: what’s the best fix for our growing obesity crisis?

Dr David Unwin thinks he has the answer. He has championed a low-carb lifestyle that not only helps patients lose weight but also, in more than half of his patients who were on the diet, has even managed to reverse type 2 diabetes, once thought to be an irreversible and progressive disease.

Such results appear remarkable and will be scrutinised by NHS officials now rolling out a national low-calorie diet programme to treat obesity and type 2 diabetes, which can lead to serious health complications and early death.

Unwin also appears to have identified what one expert calls the “magic ingredients” that motivate his patients to adhere to lifestyle changes for several years.

Unwin’s work could be pivotal. At a time when the weight-loss drug Wegovy has been approved for use in the NHS and it has been reported that officials believe such drugs could ultimately be offered to up to 12 million people in the UK, Unwin’s solution has nothing to do with drugs.

Sitting in his practice office, Unwin said he nearly quit being a GP in 2012 because he felt a sense of failure. He said: “If I was really being honest with myself, I felt I hadn’t made a difference. I began to realise that what was wrong was that nobody looked any better. The people I was seeing were sicker and fatter.”

He was inspired to start the low-carb lifestyle programme and to keep working as a GP when he was admonished by a patient diagnosed with type 2 diabetes. “I wrote to her because I was concerned she was not taking her metformin [a drug to treat type 2 diabetes] and so I was really inviting her in for a telling-off,” he said.

When the patient arrived for the consultation, Unwin discovered she had lost about 19kg (3 stone) and put her condition into remission on a low-carb diet. Research has shown such a diet can lower blood glucose levels and reduce body weight.

Unwin said: “She was hopping mad. She said: ‘You’ve given me metformin for about 10 years and you never once asked me about the side effects or gave me an alternative. I’ve now learned about cutting the carbs. I’ve lost weight and I feel fabulous.’” A blood sugar test, known as a haemoglobin A1c (HbA1c) test, showed that her blood sugar was in the normal range and that she appeared to have achieved drug-free remission from type 2 diabetes.

Unwin said: “She’d done something I didn’t know was possible. I had always seen type 2 diabetes as a chronic, deteriorating condition requiring medication and shown no curiosity about the true cause of chronic illness. I felt as if I’d been sleepwalking.”

With his wife Jen, a clinical psychologist, Unwin started a programme at the practice in 2013 offering a low-carb diet to patients with type 2 diabetes. Every Monday, there was a support group at which Unwin and his wife provided unpaid assistance. Regular weight data and blood tests helped patients stay on track.

One by one, the patients started to lose weight and feel much better. A range of markers of physical health, from blood pressure to cholesterol levels, improved. Several patients were able to give up their drugs.

The observational study published by Unwin and four other authors in BMJ Nutrition, Prevention & Health in January examined a cohort of 186 patients at the Norwood practice for an average diet duration of 33 months and found overall remission of type 2 diabetes was achieved in 51% of cases. The report found a fifth of all patients at the practice with type 2 diabetes achieved remission, with 77% of those following the programme in the first year of diagnosis achieving remission.

Marcia Mawdsley, 55, started on the diet with support from the practice about four years ago. She has lost more than 20kg and has stopped taking insulin for her type 2 diabetes. “It’s not easy in the beginning, but the first thing you notice is you don’t feel hungry,” she said. “It’s not about being thin – it’s about being healthy. I now have energy.”

Audrey Jones, 78, struggled with type 2 diabetes for years and went on Unwin’s programme last May when she was refused a hip replacement operation. She lost more than 10kg and her blood sugar test results fell significantly. Doctors gave the go-ahead for the operation in November.

Jones stopped her metformin medication for type 2 diabetes five months ago. She said: “I was absolutely delighted. I had been taking it for about five years and thought I was going to be on it for the rest of my life.”

The scale of the challenge is formidable. Nearly four decades ago, there were just 57 patients at the Norwood surgery with type 2 diabetes, which is closely associated with obesity, and none were under the age of 55. Today, the similar-sized practice has more than 470 patients with type 2 diabetes, with more than 70 under age 55.

Dr Simon Tobin, the senior partner at the Norwood Surgery in Southport, who is a keen runner and follows a low-carb lifestyle, said: “Many of our patients have been low carb for six, eight or 10 years, so it is completely sustainable. If you had a drug that did half of what we have done with the low-carb approach, it would be worth an absolute fortune. No one is shouting about it because it is not a drug that’s making a profit for a big pharmaceutical company.”

In 2016, Unwin was the national winner of the NHS Innovator of the Year award and considers he has now shown “proof of concept”, supported by the case studies of his practice’s patients and published research. Other practices in the UK and around the world have followed his work, but he would like to see the programme supported more widely in the NHS, along with proper government measures to combat obesity.

Dr David Oliver and Dr Kim Andrews set up the Freshwell Low Carb Project at the Freshwell Health Centre, near Braintree in Essex, and have reported significant weight loss in patients.

An observational study published in October 2021 reported 774 patients were given dietary advice, out of whom 339 attended a review and had their weight measured. They lost a total of 1,103kg, with a median weight loss of 2.5kg.

Dr Oliver, a senior partner at the centre, who, like Unwin and Tobin, declares no competing interests in published research, said: “When people stop eating so much processed food and carbohydrates, they are not as hungry and the weight drops off. They also feel much better.”

A report in May 2021 by the government’s Scientific Advisory Committee on Nutrition recommended adults with type 2 diabetes who were overweight could choose a low-carb diet as a short-term option (for up to six months) but should limit intakes of saturated fats, reflecting dietary advice for the general population. The report noted there was limited data on longer-term interventions with the diet.

In England the NHS is rolling out a programme of low-calorie diets to treat obesity and type 2 diabetes in primary care, which have also been shown in trials to put type 2 diabetes into remission and help participants lose significant weight.

Professor Roy Taylor, a leading researcher into type 2 diabetes and director of the Magnetic Resonance Centre at Newcastle University, who was one of the co-authors with Unwin of the research published in January, said a low-carb diet proved effective with the “magic ingredients” deployed by Unwin of structured support and regular GP checkups with weight measurement.

Taylor said many people may find it difficult to follow a low-carb diet, but there was already significant research with control groups showing a low-calorie diet can be effective in a wider population. He said the NHS rollout of a low calorie diet programme needed to be backed by a public health strategy to combat obesity, which could significantly reduce a multibillion-pound drugs bill.

Unwin is now calling for a proportion of the money that his practice, and others like it, save on drug bills to be used to fund further programmes for lifestyle treatments.

Unwin said: “We need proper remuneration and incentives that value lifestyle alternatives against long-term medication. We spend about £68,000 a year less than is average for the area on medication. I would only need half of those savings to fund further services, but there is no incentive for GP practices to do this work.”