What is this wonder method?
Exercise, according to the chairwoman of the Academy of Medical Royal Colleges Sue Bailey, and doctors need to play a vital role in making that happen.
Professor Bailey said physical activity should be classed as a "wonder drug", with the chance of developing some common cancers reduced by as much as 45% by a little regular exercise.
She made the comments in a foreword to a report by the academy into the importance of physical activity, regardless of whether or not it is linked to weight loss.
Billions of pounds spent on the NHS could be saved if people did 30 minutes of physical activity five times a week, the report said.
The risk of breast cancer could be reduced by as much as 25%, while the chances of getting bowel cancer could be lowered by as much as 45%.
Heart disease could be cut by 40%, while the risk of developing dementia could be lowered by 30%, the same percentage as stroke.
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The report followed analysis of more than 200 separate pieces of research, including studies that found that 80% of obese patients had never discussed their weight with their GP and that twice as many deaths were due to inactivity than were due to obesity on its own.
It is estimated that half the population do not do enough exercise, while less than a third of the over-65s do so.
The report offered advice to doctors on how to advise their patients to become more active and pointed out that for most people, the easiest forms of exercise were those that could be fitted into every day life, such as walking children to school.
"Doctors supporting people to be more physically active need to borrow from coaching techniques, motivational interviewing skills and psychological concepts," the report said.
Lead author and consultant orthopaedic surgeon Scarlett McNally said: "This is about reminding doctors and patients that fitting small amounts of regular exercise into their schedule can make a huge difference to their health.
"It could be as simple as taking the stairs rather than a lift, kicking a ball about with your children or grandchildren.
"We've got to change what we think of as normal, because what we are seeing in our hospitals and surgeries up and down the country is that normal has become not enough exercise.
"Too many of my patients are paying the price for that with broken bones and years of ill-health that could have been avoided by being more active."
Prof Bailey said: "This is about people and their doctors believing that the small effort involved is worth it because they are worth it.
"There really is a miracle cure staring us in the face, one which too many patients and doctors have quite simply forgotten about."
The Royal College of Physicians (RCP) said the report reinforced previous findings about physical exercise.
"As physicians. we have a key responsibility to try to incorporate messages about the impact exercise can have when talking to our patients - as the benefits are plain to see," its academic vice-president and public health lead Professor John Wass said.
"We must also move away from the idea that exercise is only for a specific short-term purpose but impress the advantages that a lifelong appreciation of physical activity can bring."
Dr Maureen Baker, chairwoman of the Royal College of GPs, said the findings about the extent of the benefits of exercise were "astounding".
"GPs are well-placed to educate our patients about the benefits of leading a healthy lifestyle and today's report shows how incorporating a modest amount of exercise into our daily routines can ensure our long-term health," she said.
"But simply telling patients what to do is not enough - long term behaviour change is very hard and requires ongoing support and access to help over time.
"We need more resources in general practice and more GPs so that we can spend more time with our patients on preventing them getting ill, as well as caring for them when they are ill."
Dr Mike Brannan of Public Health England said: "Physical activity is crucial for physical and mental health.
"Doctors play an important role in providing patients with information to make positive choices about their health.
"Embedding messages on the long and short-term benefits of physical activity into their everyday practice and patient care is key."