Exercise can be as good a medicine as pills for people with conditions such as heart disease, a study has found.
The work in the British Medical Journal (BMJ) looked at hundreds of trials involving nearly 340,000 patients to assess the merits of exercise and drugs in preventing death.
Physical activity rivalled some heart drugs and outperformed stroke medicine.
The findings suggest exercise should be added to prescriptions, say the researchers.
Experts stressed that patients should not ditch their drugs for exercise - rather, they should use both in tandem.
Too few adults currently get enough exercise. Only a third of people in England do the recommended 2.5 hours or more of moderate-intensity activity, such as cycling or fast walking, every week.
In contrast, prescription drug rates continue to rise.
There were an average of 17.7 prescriptions for every person in England in 2010, compared with 11.2 in 2000.
For the study, scientists based at the London School of Economics, Harvard Pilgrim Health Care Institute at Harvard Medical School and Stanford University School of Medicine trawled medical literature to find any research that compared exercise with pills as a therapy.
They identified 305 trials to include in their analysis. These trials looked at managing conditions such as existing heart disease, stroke rehabilitation, heart failure and pre-diabetes.
When they studied the data as a whole, they found exercise and drugs were comparable in terms of death rates.
But there were two exceptions.
Drugs called diuretics were the clear winner for heart failure patients, while exercise was best for stroke patients in terms of life expectancy.
Amy Thompson, senior cardiac nurse at the British Heart Foundation, said that although an active lifestyle brings many health benefits, there is not enough evidence to draw any firm conclusions about the merit of exercise above and beyond drugs.
"Medicines are an extremely important part of the treatment of many heart conditions and people on prescribed drugs should keep taking their vital meds. If you have a heart condition or have been told you're at high risk of heart disease, talk to your doctor about the role that exercise can play in your treatment."
Dr Peter Coleman of the Stroke Association said exercise alongside drugs had a vital role that merited more research.
"We would like to see more research into the long-term benefits of exercise for stroke patients.
"By taking important steps, such as regular exercise, eating a balanced diet and stopping smoking, people can significantly reduce their risk of stroke."
"Moderate physical activity, for example, can reduce the risk of stroke by up to 27%."