Almost 5,000 cases of bowel cancer in Scotland over the last decade have been caused by obesity, according to a leading charity.
The findings have been described by Cancer Research UK as a “huge worry”.
The charity has called for restrictions on offers for unhealthy food and more done to encourage healthier lifestyles.
The Scottish government has said it will examine what further action it can take, including measures on multi-buy promotions.
There are around 3,800 cases of bowel cancer diagnosed in Scotland each year and about 1,600 people die from the disease annually.
Obesity is linked to 13 types of cancer and Cancer Research UK said resistance to insulin, a hormone important in the breakdown of food, is one likely explanation.
Scientists have found high levels of insulin in the body causes cells to divide more rapidly, raising the likelihood of the cells changing and leading to cancer.
Cancer Research UK has warned the proportion of bowel cancer cases caused by obesity is on the increase as more of the population becomes overweight.
It claimed shoppers were “bombarded” by offers encouraging them to stock up with food that leads to weight gain. It now wants a restriction on such multi-buy deals.
Prof Linda Bauld, Cancer Research UK’s cancer prevention expert based at the University of Stirling, said: “It is a huge worry to see so many bowel cancer cases being caused by excess weight, and to see that proportion rising as more of the population becomes overweight or obese.
“It is also now more common for adults in Scotland to be overweight or obese than a healthy weight.
“In the face of this, the Scottish government has a responsibility to take action and introduce an obesity strategy which will help everyone to make healthy choices.
“Cancer Research UK believes restricting multi-buy offers on unhealthy foods and drinks would go a long way to improving the health of the nation.
“The Scottish government can and must do more and its forthcoming strategy is a once-in-a-generation opportunity to introduce measures that will have a profound impact on our lives.”
Scottish ministers are planning a new diet and obesity strategy.
Minister for Public Health and Sport Aileen Campbell said: “As part of that, we are looking at what further effective actions we can take within the powers available to us, including action on the use of multi-buy promotions.
“We are also engaging with the food and drink industry on action to offer healthier choices, rebalance promotions, and reformulate products, with a focus on reducing calories, salt, fats and added sugar.
“Last year we launched our 100m Cancer Strategy, which will serve as a blueprint for the future of cancer services in Scotland, improving the prevention, detection, diagnosis, treatment and aftercare of those affected by the disease.”