According to the latest research, patients suffering from prostate cancer who are overweight or obese are more likely to die of their disease.
Nevertheless, the scientists didn’t manage to find any association between obesity and developing the prostate cancer in the first place.
"Although we didn’t discover that obesity increases the risk of experiencing prostate cancer, we managed to find that it does actually increase the risk of dying from it. Therefore, this research truly sheds more light on the obesity connection," said lead author of the study, Margaret E. Wright, a research fellow with the division of Cancer Epidemiology and Genetics at the National Cancer Institute.
The findings were published in the February 15 issue of Cancer. Wright and her team emphasized that as recently as 2000, almost 66 per cent of American citizens of both genders were classified as overweight or obese.
Overweight tied to a variety of risks
Previous studies had not uncovered a clear connection between obesity and a greater risk for the beginning of prostate cancer, however the authors observed that excess weight is clearly associated with risk increases for type 2 diabetes, cardiovascular disease, chronic illnesses and many other kinds of cancer.
Prostate cancer affects one in six men and is the most widespread type of non-skin cancer in the United States, according to the data of American Prostate Cancer Foundation. Risk increases along with age, with over 65 per cent of all cases diagnosed in men over the age of 65.
In terms of risk factors, both genetics and lifestyle choices - especially diet and exercise habits- are believed to play a role.
How the research was carried out
Concentrating on body mass index - a ratio of weight to height - as one potential risk factor for the beginning and development of prostate cancer, Wright and her team evaluated health questionnaires completed by almost 288 000 men who were between the ages of 50 and 71 when the research began in 1995.
All the men were members of AARP and were taking part in a larger diet and health research started by the organization. In the smaller BMI sample, none of the men had been previously diagnosed with cancer, with the exception of non-melanoma skin cancer.
The preliminary questionnaire - as well as a consequent 1996 follow-up completed by almost 173 000 of the subjects - gathered information concerning height, weight, BMI, and the frequency with which patients underwent prostate-specific antigen (PSA) testing and digital rectal exams (DRE) in the three years before the research.
The scientists observed that when the research started, about 29 per cent of the men were normal weight, a half of them were overweight and 21 per cent were obese.
From the beginning of 1995 to the end of 2000, Wright and her colleagues discovered that nearly 10 000 of the men developed prostate cancer. By the end of 2001, 173 of these men had died of the illness.
Risk increases with BMI
The authors of the research discovered that the risk of death from prostate cancer turned up to rise as BMI increased. In comparison with men of normal weight, overweight men were at a 25 per cent greater risk of dying of the disease. Slightly obese men - those with a BMI between 30 and 34.9 - had a 46 per cent greater risk. And seriously obese men - those with a BMI of 35 or more - had double the normal risk of death.
Furthermore, the more weight a man gained after the age of 18, the higher the risk of dying if diagnosed with prostate cancer.
There were many factors, such as age, race, family history of prostate cancer, and screening history that did not seem to have any influence on the observed connection between too much weight and fatality risk.
The authors indicated that their research was the very first one to uncover evidence of the BMI-prostate cancer fatality connection.
"This is a large research, and this finding really solidifies previous suggestions indicating that this connection is real," she said. "So whereas we still have to conduct more studies to find out exactly how this works, I’m not astonished with the association."
We have to fight obesity
"We have to keep on addressing the increasing occurrence of obesity in this country and others," Wright added, "due to the fact that obesity is connected with many, many diseases. So we would, of course, definitely suggest that people maintain a healthy weight through diet and physical activity."
According to Dr Philip Arlen, director of the Clinical Research Group in the Laboratory of Tumour Immunology and Biology with the Centre for Cancer Research at the US National Cancer Institute, the existence of the apparent connection between obesity and prostate-cancer mortality was not astonishing.
"This adds to observations in several different studies that suggest that patients who are in better condition - thinner, more active, or with a lower BMI - may develop a less aggressive type of cancer and do better than patients with a sedentary lifestyle," explained Arlen. He did not belong to the team of scientists.
"There are many various factors that may play role, and BMI may not be predictive in terms of experiencing prostate cancer," he added. "But it seems that among patients already diagnosed with this illness, those who are physically active and not obese may face a better outcome."
