Yes agree with prevention.
So that means holistic care - which means addressing the issues that so often prevent people having a healthy lifestyle (because lifestyle frequently isn't a choice).
Although not the only two causes, poverty and stress (both often interlinked) are major ones. NHS demand would dramatically reduce with:
More council housing, a supportive benefits system, jobs education and training opportunities, and timely access to well-funded and good public services - including the NHS but also social services and other support services.
Poverty means lack of access to affordable healthy food. More deprived areas often have only smaller convenience stores nearby that have limited stock at often more expensive prices than larger supermarkets and mainly stock unhealthy processed food. Then there's the limited cooking and storage facilities in many homes.
And it's known, through studies by medical experts, that chronic stress can cause weight gain.
One of the biggest issues is housing. As published in the BMJ, bad or insecure housing harms health. More council housing is needed asap. That will significantly reduce demand on the NHS (and reduce disability benefit need, plus save the economy billions that's currently needed for high private rental housing benefits and temporary accommodation).
Another cause of weight gain and/or poor health is NHS delays, the doctor fobbing off culture, and misdiagnoses. By the time people are correctly diagnosed and treated, they're in worse health and need more (and more expensive care). In the meantime they gain weight due to pain or limited mobility that makes exercise difficult.
End the false economy approach of insufficient 5-10 minute GP appointments that make it easy to misdiagnose or dismiss symptoms, until people are more unwell. Have prompt access to diagnostic tests.
People might claim all the above costs money. However, the alternative - the current system - is a false economy.