Women aged over 50, who attend routine breast screening appointments, will be asked to take part in the trial ActWell in Aberdeen, Dundee, Edinburgh and Glasgow.
Funded by the Scottish Government, the research trial will be led by the University of Dundee and supported by charity Breast Cancer Now.
The scheme could also be rolled out to other NHS Boards following a successful pilot.
The charity is seeking 24 volunteers to train as lifestyle coaches to support the trial.
They will work with women to help them make lasting changes focused around physical activity, diet and weight.
Around 4,600 women in Scotland are diagnosed with breast cancer every year and around 1,000 lose their life to the disease annually.
Experts estimate that 38% of breast cancer cases in post-menopausal women could be prevented by lifestyle changes linked to inactivity, poor diet, alcohol consumption and weight.
Health Secretary Shona Robison said: “Prevention is a key part of our cancer strategy.
“We know things like weight, diet and activity levels can all significantly contribute towards your risk of developing cancer.
“With breast cancer risk in women over 50, the link is particularly pronounced.
“By recruiting volunteers to work as lifestyle coaches, this scheme will test whether we can reduce those risks and save women and their families from having to face up to a cancer diagnosis.”
Mary Allison, director for Scotland of Breast Cancer Now, said: “The trial has the potential to have a significant impact on reducing the risk of breast cancer in Scottish women.
“Recruiting lifestyle coaches will be integral to the success of ActWell.
“We’re looking for people with an interest in health and lifestyle.
“We want to attract those who are keen to make a difference to women’s lives.”
Annie Anderson, Professor of Public Health Nutrition at the University of Dundee and co-director of the Scottish Cancer Prevention Network, said: “An increased emphasis on prevention is vital if we are to combat breast cancer.
“Physical inactivity, diet, alcohol consumption and body weight are all significant risk factors in developing the disease.
“With the study we are looking to support women with ActWell lifestyle coaches and access to services that can help reduce these risks.
“This starts with a 30-second conversation at the breast screening centre but it could have life-changing effects.
“Our pilot study showed considerable benefits for women aged over 50 which is extremely encouraging.”