Exercise may be just as good as medication to treat heart disease and should be included as a comparison when new drugs are being developed and tested, scientists said on Wednesday.

In a large review published in the British Medical Journal, researchers from Britain's London School of Economics and Harvard and Stanford universities in the United States found no statistically detectable differences between exercise and drugs for patients with coronary heart disease or prediabetes, when a person shows symptoms that may develop into full-blown diabetes.

For patients recovering from stroke, the review - which analysed the results of 305 studies covering almost 340,000 participants - found that exercise was more effective than drug treatment.

Cardiovascular disease is the world's number one killer, leading to at least 17 million deaths a year.

"In cases where drug options provide only modest benefit, patients deserve to understand the relative impact that physical activity might have on their condition," the researchers wrote.

The review also said the amount of trial evidence on the health benefits of exercise is considerably smaller than that on drugs, which the scientists said may have had an impact on their results.

They argued that this "blind spot" over exercise in scientific evidence "prevents prescribers and their patients from understanding the clinical circumstances where drugs might provide only modest improvement but exercise could yield more profound or sustainable gains".

The review adds to a large body of evidence showing that regular exercise is key to human health.

According to the Geneva-based World Health Organization (WHO), physical inactivity is the fourth leading risk factor for global mortality, causing an estimated 3.2 million deaths around the world each year.

The WHO says regular moderate intensity physical activity - such as walking, cycling or participating in sports - can reduce the risk of cardiovascular diseases, diabetes, colon and breast cancer, and depression, as well as cutting the risk of bone fractures and helping to control body weight.

In the United States, where health experts estimate half of adults will be obese by 2030 unless lifestyle habits change, the Centers for Disease Control and Prevention says less than 48 percent of adults exercise enough to improve their health. – Reuters