When the Labour deputy leader, Tom Watson, told me he’d found it “relatively easy” to lose 94lbs in 10 months after following the plan outlined in my book The Pioppi Diet, I felt we were close to a tipping point in reversing the twin epidemics of type 2 diabetes and obesity.

By reducing starch and sugar, Watson has also managed to send his type 2 diabetes into remission. His story reflects what the science is telling us: a systematic review comparing a healthy low-carbohydrate diet versus a healthy low-fat diet published in the American Journal of Clinical Nutrition last month revealed the former to be superior for glucose control, as well as for limiting heart disease risk factors in the short and long term for type 2 diabetics.

But in addition to individuals making diet and lifestyle changes, policy changes are also essential to tackling the most important root cause of the obesity epidemic: the obesogenic food environment. The success and sustainability of healthy dietary changes will only occur if we make the healthy choice the easy choice.

It’s a scandal that we’ve even allowed our hospitals to become a sales opportunity for the junk food industry. At one London hospital I worked in, a contract with a high street retailer ensured chocolates, crisps and sugary drinks were delivered on trolleys to patients.

It’s no surprise that 60% of nurses and 49% of other healthcare professionals in England are overweight or obese – obesity is rooted in the food environment, and hospitals are no different from the high street, where it’s become almost impossible to avoid the ultra-processed food that now makes up half of the British diet. Back in 2013, the British Medical Association passed my motion calling for the sale of junk food to be banned in hospitals. But this aspiration is yet to be made a compulsory target.

One hospital and borough in Greater Manchester has taken matters into its own hands. Tameside residents were encouraged to go on a 70-day sugar-free challenge to mark the 70th anniversary of the NHS.

The challenge was inspired after the local hospital was the first in the country to ban sugary drinks and food from its canteen. Simon Smith, who has a background in dietetics and a strong family history of type 2 diabetes, took over as head chef of the hospital in May last year. He said The Pioppi Diet “catalysed” a discussion with the chief executive, Karen James, to transform the food served to staff.

As a local boy who grew up in the area, I was invited to deliver a keynote lecture at Hyde town hall launching the challenge in July, where I explained the scientific basis behind the plan and how dietary changes can rapidly improve health and weight.

More than 100 healthcare professionals and members of the public have fed back their results, which reveal an average of 4-10kg weight loss over the 70 days, and dozens of testimonials of an improved sense of wellbeing.

Midwife Sarah Davies, 41, said she lost two stone, and reported feeling healthier than she had in years. Her husband Matty, a 40-year-old fireman, lost more than three-and-a-half stone.

Although this is clearly not a clinical trial, it highlights what can be achieved through simple diet and lifestyle advice. Hopefully such positive feedback will inspire other members of the community and hospitals to follow suit.

If a grassroots movement such at Tameside’s was combined with top-down political support, it could be the start of a much-needed revolution to finally reverse obesity and related chronic disease trends, and allow the NHS to survive another 70 years.

• Aseem Malhotra is consultant cardiologist and visiting professor of evidence-based medicine at Bahiana School of Medicine and Public Health, Brazil. He is co-author with Donal O’ Neill of The Pioppi Diet and is donating all personal royalties from the book to charity.