While it’s easy to think of the steady accumulation of belly fat as an inevitable part of midlife, experts are increasingly realising that having a “spare tyre” around your midriff can be a ticking time bomb when it comes to your risk of aggressive prostate cancer.
At Imperial College London, cancer biologists are in the midst of a groundbreaking new project that is attempting to understand why excess body fat – particularly harmful layers of internal or visceral fat which accumulate around the prostate – can predispose middle-aged men to the deadliest forms of the disease.
With one in eight men in the UK affected by prostate cancer at some point in their lives and rapidly spiralling obesity rates – an astounding 67 per cent of men in this country now classify as either overweight or obese – the race is on to try to understand more.
According to Dr Claire Fletcher, one of the researchers leading the project, which is funded by the charity Prostate Cancer Research, the findings could help yield improved screening to pinpoint those who are particularly vulnerable and even new treatments.
“Although detailed knowledge about how fat fuels aggressive prostate cancer is limited, we do know that the amount of fat around a patient’s prostate, called periprostatic fat, is linked to more rapid disease progression and poorer response to treatment,” says Fletcher.
Last year, a study of 2.5 million men across Europe from nutritional epidemiologists at the University of Oxford reported that greater levels of body fat increase the risk of dying from prostate cancer by up to 10 per cent. Excess layers of fat around the belly and waist were seen to be particularly problematic, with a mere 5 per cent increase in waist-to-hip ratio increasing the risk of fatal prostate cancer by 6 per cent.
Men in their 50s and 60s are at the greatest risk of prostate cancer and, overall, the research team estimated that if the average 55- to 64-year-old male in the UK reduced their body mass index to within the ideal range of 18.5 to 24.9, there would be 1300 fewer prostate cancer deaths per year.
“There have been many studies linking a high-fat diet with an increased risk of death from prostate cancer in both prostate cancer models and people,” says Dr Naomi Elster, the director of research at Prostate Cancer Research.
But why is it that fat has such a lethal connection with this cancer?
A deadly crosstalk
As part of their research, Fletcher and her colleagues are analysing fat cells from around the prostate, along with tumour samples taken from obese men undergoing surgery to treat their cancer.
So far this has shown that the fat cells and prostate cells appear to talk to each other through a range of chemical signals that are released into the area surrounding the prostate. These signals seem to be very different in obese men compared with their lighter counterparts and might be telling the prostate cells to grow, leading to cancer. This crosstalk then continues after the person develops the disease, fuelling the tumours to grow more rapidly and ultimately spread to other parts of the body.
“It’s thought that the fat around the prostate in obese men releases more nutrients and other signals that cancer cells can use to fuel their growth,” says Fletcher. “The fat cells also produce molecules, which we call mini-cells, which essentially parcel up information and transfer it to prostate cancer cells, a little like delivering a letter. The cancer cells read the content and then alter their behaviour.”
Once prostate cancer is established, it seems that prostate cancer cells can even reprogram the surrounding body fat to act as a dedicated nutritional resource to further fuel the survival and growth of the cancer, helping it resist treatments such as hormone therapy and chemotherapy.
Improving prevention and treatment
At the same time, understanding the complex interaction between body fat and the prostate could help improve the treatment of the disease.
Fletcher says that the mini-cells that act as messengers between fat and the prostate could be used as new drug targets for the most aggressive forms of prostate cancer to improve patient survival. Right now, data from Cancer Research UK shows that 50 per cent of all men with the most lethal forms of the disease will die within five years.
Being able to identify these molecules through blood or urine tests soon after a patient is diagnosed could also help personalise the treatment pathways for different patients.
“This might allow us to monitor at-risk men, to catch dangerous cancers early when they have a better chance of successful treatment, or it could be used by doctors to identify when a patient needs more aggressive upfront treatment,” says Fletcher.
Another hope is that the data that emerges from the project can be used in support of government and NHS-backed weight-loss programmes. Fletcher points out that a common side effect of hormone therapies for prostate cancer is an accumulation of belly fat, which in some cases may fuel the disease.
“Results from our study may allow us to lobby policymakers for the introduction of assisted healthy lifestyle interventions such as exercise and dietary changes alongside such treatments to reduce side effects and boost treatment response,” she says.
However, Elster says that rather than being judgmental about obesity, she hopes this research will yield more treatment options that work effectively for all prostate cancer patients, whatever their weight.
“There are so many reasons an individual might be overweight or obese, and many of those reasons might be out of our control, such as genetics, poverty and lack of access to healthy food, or underlying medical issues,” she says. “We must make sure that effective treatment options exist that work for all prostate cancer patients, whether they are a healthy weight, overweight or obese.”
How to reduce belly fat
- Choose a diet that works for you, and that you can stick to, like writer Ben Rowell found with his Ten Pound Diet. Intermittent fasting has been shown to be good for your gut, and the diet with the most research showing that it’s good for your health is the Mediterranean diet.
- Minimise sugar, processed snacks, and high-fat ready meals - try to cook from scratch as much as possible with real, not packaged, foods.
- Move every day and incorporate strength training into your workouts, as muscle burns more calories and boosts your metabolism, particularly in midlife.
- Drink in moderation, as alcohol contains empty calories that fuel weight gain.
- Stress is thought to be a cause of visceral fat around your belly, as the stress hormone cortisol can increase the amount of it we store. Although easier said than done, implementing stress-management strategies into your daily routine - like yoga, mindfulness and walks outside - is a good way to manage this.
- For more information, see the Prostate Cancer Foundation NZ website