A study suggests that healthy people who are on the verge of becoming overweight may be at an increased risk of developing bowel cancer.
It has found that such people are about 15 per cent more likely to develop bowel cancer than those at the lower end of the range.
Professor Martin Wiseman, a medical and scientific adviser for the World Cancer Research Fund (WCRF), says that it is possible to prevent about 18,600 cancer cases if people had a body mass index (BMI) under 25.
A BMI of 25 to 30 is classed as overweight and over 30 is obese.
The WCRF recommends that people aim to be as lean as possible without becoming underweight to avoid the cancers of the breast, bowel, oesophagus, kidney, pancreas, womb, and gallbladder.
Wiseman says that that means that people should aim to be closer to a BMI of 18 than 25, even within the healthy weight range.
"The evidence that being overweight puts you at increased risk of cancer is stronger now than ever before and we now say that, after not smoking, maintaining a healthy weight is the most important thing you can do for cancer prevention," the Telegraph quoted him as saying.
"This is the reason we recommend people aim to be as lean as possible without becoming underweight.
"But a recent survey showed almost 40 per cent of people still do not know that excess body fat is a cause of cancer. This means we need to do more work to spread the message that maintaining a healthy weight is something positive people can to reduce their risk of developing cancer later in life," he added.
Health experts are of the opinion that people one in three cases of the most common cancers could be avoided if people ate healthily, took more exercise, and maintained a healthy weight.