A new study says more than 1,300 prostate cancer deaths could possibly be prevented each year in the UK if the average man was not overweight. While obesity has been linked to 13 other cancers - including in the stomach, liver, pancreas and kidney - the connection between prostate cancer and weight has only just started to be unpicked by scientists.
The new study is being presented at the European Congress on Obesity in the Netherlands and published in the journal BMC Medicine. As part of the research, experts examined data on 218,237 men enrolled in the UK Biobank study whose body mass index score (BMI), waist circumference and waist-to-hip ratio were taken when they first enrolled in the study.
The participants were tracked for an average of 12 years, with 661 men dying from prostate cancer in the follow-up period. After analysing the health data on the men who died from prostate cancer, and comparing it to those who did not, the researchers found that for every five additional points on a man's BMI score they were 7% more likely to die from prostate cancer.
And they had a 6% higher risk of dying of prostate cancer for every extra 4in (10cm) on their waistline. Meanwhile, researchers also performed an analysis of previous studies which looked at information on almost 20,000 men who died from prostate cancer.
These studies suggested that for every five additional points on a man's BMI score they were 10% more likely to die from prostate cancer, and an additional 4in (10cm) waist size carried a 7% higher risk. While the mechanisms behind the findings are still unknown, researchers said the study still suggests that men should try to maintain a healthy weight.
"Knowing more about factors that increase the risk of prostate cancer is key to preventing it," said Dr Aurora Perez-Cornago, from the University of Oxford, who led the research. "Age, family history and black ethnicity are known risk factors but they are not modifiable, and so it is important to discover risk factors that it is possible to change."
Each year in the UK, around 11,900 men die from prostate cancer. And the researchers said that men aged 55 to 64 have an average BMI score of 28.9 – which classes them as overweight.
Based on their findings, they calculated that if men were able to shave five points from their BMI score then an estimated 1,309 fewer prostate cancer deaths would happen every year in Britain. And they pointed out that global health leaders recommend that men should aim to have a waist circumference of 36in (92cm).
Karis Betts, senior health information manager at Cancer Research UK, which funded the study, said: "This research looks at the likelihood of dying from prostate cancer for people who are overweight or obese, but further studies to investigate whether obesity increases the risk of developing prostate cancer in the first place are needed. While the jury is out on the relationship between prostate cancer and obesity, it's still important to keep a healthy weight as obesity causes 13 other types of cancer.
"However, by building on these useful findings in future, scientists can start to unpick what the mechanism of prostate cancer and obesity could be, helping them to better understand who is at an increased risk of getting and dying from the disease."
Simon Grieveson, from Prostate Cancer UK, said: "Whilst these results are compelling, more research is needed to fully understand the biological relationship between obesity and prostate cancer and, most importantly, how we can use this information to improve outcomes for men. Maintaining a healthy weight can protect against many cancers, but it is important to remember that prostate cancer can affect men of all shapes and sizes."
Meanwhile, a different study published at the conference found that poor sleep may undermine a person's attempts to keep weight off. Experts from the University of Copenhagen in Denmark looked at sleep duration and quality among 195 obese adults.
Those who slept for less than six hours per night were found to have, on average, increased their BMI score by 1.3 points after a year compared with those who slept for more than six hours. Similarly, poor sleepers – measured with a self-rated questionnaire – increased their BMI score by 1.2 points after a year compared with good sleepers.
The academics found that around two hours of vigorous physical activity per week can help people sleep better. Another study presented at the meeting concluded that almost a quarter of obese teenagers do not know they are in fact obese.
