Obesity, visceral adiposity, and prostate cancer: What is the role of lifestyle interventions?

Abstract

The findings from Dickerman et al's research highlight the need to consider and implement lifestyle interventions to target weight loss and the risk of prostate cancer. Interventions that combine 2 lifestyle behaviors, diet and exercise, may be most impactful.

Excess body fat has long been recognized as a serious health risk, with the World Health Organization identifying obesity as a global health epidemic more than 20 years ago.1 Since that time, research has continued to demonstrate the negative impact of excess body fat by showing associations between obesity and metabolic syndrome, type 2 diabetes, cardiovascular disease, sleep-related breathing abnormalities, infertility, osteoarthritis, and liver and gallbladder disease.2 Obesity has also previously been associated with certain cancers, particularly cancers targeting the colon, breast (among postmenopausal women), endometrium, esophagus, and kidneys, as well as advanced prostate cancer. Although targeting obesity has remained critical, research is also focusing on the importance of the location of fat tissue, with particular concerns centering on visceral fat.3, 4 High levels of visceral fat have been associated with a large number of medical conditions, including insulin resistance, type 2 diabetes, hypertension, and cardiovascular disease, as well as all-cause mortality.3-6

In novel research building upon this evidence for the importance of the distribution of body fat to the risk of disease,3-6 Dickerman et al7 conducted a prospective examination of whether fat distribution was associated with prostate cancer outcomes. Working with cohort data from the Age, Gene/Environment Susceptibility–Reykjavik (AGES-Reykjavik) study, the investigators used computed tomography imaging of fat in the abdomen and thigh as well as prostate cancer outcomes to identify associations between visceral fat and the risk of advanced disease and between thigh subcutaneous fat and the risk of fatal prostate cancer. The association between visceral fat and advanced and fatal disease held, and indeed was stronger, among men with a lower body mass index (BMI). Although the study presents an advancement in considerations of fat distribution and prostate cancer, it is important to consider 2 points. First, the BMI cutoff for lean men was based on participant median values. As such, men with BMIs under 27 kg/m² were considered lean when, traditionally, this classification would include both normal-weight men and overweight men, who would likely have higher visceral fat. This BMI categorization may influence the generalizability of findings. Second, fat in multiple locations (ie, visceral fat and thigh subcutaneous fat) was associated with clinically relevant prostate cancer. This supports existing evidence for the link between body fatness, regardless of location, and advanced prostate cancer indicated previously.

The findings from Dickerman et al's research,7 in addition to existing evidence on obesity and prostate cancer, highlight the need to examine lifestyle interventions that target fat loss in promoting optimal prostate cancer outcomes. Two lifestyle behaviors frequently examined within weight-loss research are diet and exercise. These behaviors are targeted because of their influence on energy balance.8-11 When each lifestyle behavior is considered separately, diet is a commonly used and effective method for targeting weight loss because exercise has limited impact on total weight loss.12, 13 Although many types of diets have been studied (eg, low-carbohydrate, low-fat, high-protein, and Mediterranean diets), a recent meta-analysis has found that a low-carbohydrate/high-protein dietary intervention results in the greatest weight loss.12

However, in light of the strong emphasis in the article on the findings associating visceral fat and advanced prostate cancer among men with lower BMIs and in light of existing knowledge on the detrimental impact of visceral fat, there is also a need to determine what behavior may be most effective in targeting this regional fat distribution. In these cases, exercise may be particularly beneficial.10, 14, 15 For example, in research comparing overweight men with high and low levels of fitness, those with higher levels of fitness had significantly lower visceral fat, and this suggests that physical activity targeting fitness may be critical in reducing visceral fat.16 Indeed, regardless of total body weight or weight loss, increases in physical activity, more specifically exercise, have been related to significant decreases in visceral fat.10, 14

Because of the importance of both behaviors in targeting fat loss identified as necessary by the current analysis from the AGES-Reykjavik study, it may be most beneficial to frame lifestyle interventions for prostate cancer with an approach that combines both behaviors—in this case, diet plus exercise. Existing research and meta-analyses support the beneficial impact of combining both behaviors for achieving greater weight loss.17, 18 The goal of intervening with these combined behaviors would be to reduce body fat, with a particular emphasis on visceral fat, without a decline in muscle mass. As a result, although many interventions use aerobic-based approaches, resistance training may be important for achieving optimal changes in body composition.17

In light of the findings by Dickerman et al7 and the existing body of knowledge on diet and exercise, new opportunities arise for knowledge development and practice for researchers and clinicians. First, researchers could benefit from including measures that assess visceral fat as outcomes in interventions, whereas clinicians would benefit from collecting knowledge of fat location in addition to the total weight. This information, alongside existing outcome measures such as inflammatory markers, may be beneficial in indicating whether prostate cancer risks are being targeted during treatment.

Second, the research provides support for the importance of the timing of lifestyle interventions. According to the information provided by Dickerman et al7 on the cohort in the AGES-Reykjavik study, optimal benefits may be experienced prior to diagnosis through early preventative interventions. Within the AGES-Reykjavik study, the men who demonstrated higher visceral fat also had lower self-reported physical activity during youth and midlife. Although a direct association was not made, through knowledge of the importance of diet and physical activity in targeting fat, interventions should potentially prioritize targeting these lifestyle factors during youth or emerging adulthood in order to decrease the risk of prostate cancer. Indeed, research on physical activity and prostate cancer suggests that adolescence and young adulthood may be optimal years for preventive behaviors such as physical activity.19 In sum, the evidence linking fat and particularly fat distribution to prostate cancer outcomes opens a number of directions for enhancing the direction and quality of lifestyle interventions.

Funding Support

No specific funding was disclosed.

Conflict of Interest Disclosures

The authors made no disclosures.