The World Health Organisation is advising people engage in at least 150 minutes of "moderate" physical exercise a week to reduce the risk of breast and colon cancers, in new recommendations published Friday.

"Cancer is preventable and many cancers are avoidable," said Eduardo Cazap, president of the Union for International Cancer Control (UICC) and one of the authors of the joint "Global Recommendations on Physical Activity for Health".

UICC and WHO experts estimate based on scientific evidence that around 25 percent of breast and colon cancers could be prevented by undertaking physical activity, while exercise can also affect other types of cancers.

"The dose of physical activity required is 150 minutes a week," WHO health promotion expert Tim Armstrong told journalists.

"Most individuals can accomplish it, it's 30 minutes of moderate effort like walking on five days of the week," he explained.

The WHO ranks lack of physical activity alongside tobacco, diabetes and high blood pressure as a health risk, leading to the deaths of 3.2 million people a year.

"Physical inactivity is the fourth leading risk factor for all global deaths, with 31 percent of the world's population not physically active," said Dr Ala Alwan, WHO assistant director-general for non-communicable diseases and mental health.

Some 460,000 women died as a result of breast cancer in 2008 while about 610,000 died of colorectal cancers, according to UN health agency data.

Cazap underlined that one person in two is likely to have a cancer in their lifetime, and the probability grows with ageing.

The UICC believes that the problem of physical inactivity is now extending beyond industralised nations to emerging nations where the population is becoming wealthier.

The recommendations were released for World Cancer Day on Friday. AFP