Newly diagnosed cancer patients should be told to diet and exercise, amid mounting evidence that shedding the pounds is the best way to fight the disease, global experts have advised.
A daily brisk walk of just 25 minutes was found to almost halve mortality among breast cancer sufferers, while a waistline larger than 35 inches increased death rates by one third.
Results from a slew of trials showed “powerful” and “groundbreaking” evidence of the benefits of a slim waistline, with weightloss and exercise helping even those with advanced cancer.
Even those who took little exercise before diagnosis saw major benefits, experts told the world’s largest cancer conference, in Chicago.
Leading oncologists said a cancer diagnosis offered a “window of opportunity” to convince patients to make lifestyle changes which could prolong their lives.
They said those receiving a diagnosis should be warned to lose weight and take more exercise, even if such conversations were “sensitive”.
One expert at the American Society of Clinical Oncology’s annual conference, launching the first trial into high intensity exercise for prostate cancer patients, said the NHS should prescribe personal trainers for those diagnosed with cancer.
Obesity is linked to more than 10 types of the disease, including breast, bowel and ovarian cancer.
But until now, much of the emphasis has been on preventing weight gain to reduce the chances of developing the disease, rather than raising the issue in patients with cancer.
Prof Melinda Irwin, Associate Director of Cancer Prevention for Yale Cancer Center, said diagnosis was a time for patients to make lifestyle changes.
She said: “After treatment, weight loss is the most powerful thing you can do. It’s the next best pill to treatment and it’s free and has no side effects.”
Prof Irwin said doctors needed to be “sensitive” in raising the issue with newly diagnosed patients, but should not duck the issue.
“Every woman diagnosed with breast cancer should be being counselled about weight loss and weight management, and about the role of exercise,” she said.
“Diagnosis offers a window of opportunity, and diet and exercise can have a profound and powerful effect.”
Yale research led by Dr Irwin tracking almost 5,000 breast cancer sufferers found that three hours brisk walking a week was linked to a 46 per cent fall in mortality. Even when women took up such regimes after decades of sedentary living, death rates fell by as much as 33 per cent.
The observational study could not prove that the exercise caused the gains.
But a raft of studies by Yale released in Chicago this week will reveal direct evidence about the mechanisms activated via weight loss and exercise.
Dr Irwin said she was particularly excited about results from the first ever randomised controlled trial looking at the impact of exercise on ovarian cancer.
More than half the women in the six month trial had advanced disease.
But those enrolled in a walking programme, doing at least 20 minutes a day of exercise saw “profound changes” in key biomarkers which reflect cancer progression.
“This is absolutely ground-breaking. These were women with late stage ovarian cancer. They were able to exercise and willing to and having very favourable results,” she said. The study of 144 women, found the half who were prescribed exercise saw a 27 per cent drop in levels of leptin, a hormone associated with cancer, and a 15 per cent decrease in IGF-1, a natural human growth hormone which fuels cancer spread.
The cancer expert said doctors needed to be careful in raising the issue, and not leave cancer sufferers feeling that they were to blame for getting the disease.
The findings came amid the launch of the world’s largest randomised controlled trial tracking impact of diet and exercise on breast cancer sufferers, in which 32,000 women will be monitored for three years.
Meanwhile, research on more than 4,000 breast cancer sufferers, involving Stanford and Harvard universities found that women carrying excess fat on the waistline had mortality rates one third higher.
The 10 year study found that having too much fat around the stomach – meaning a waistline of more than 35 inches – was enough to increase death rates by 31 per cent, the study found.
Lead researcher Professor Rowan Chlebowski said overweight and obese women only needed to lose 5 per cent of their body weight to boost survival odds.
“A modest amount of weight loss can really have great, beneficial health benefits,” the expert said.
Fran Woodard, executive director of policy at charity Macmillan Cancer Support, urged doctors not to shy away from difficult conversations.
She said: “Asking a person with cancer about their lifestyle habits when they have just been diagnosed can be challenging and must be done sensitively. However this is an issue too important to tiptoe around.”
Another Yale study of 221 women with breast cancer found that achieving 6 per cent weight loss on average resulted in a 5 per cent decrease in a signal protein, vascular endothelial growth factor, which is known to fuel cancer.