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Obesity and cancer: Beware the festive season
It is the festive season, and most of our population is focused on eating, drinking and the creation of merriment.
The number of hospital or clinic parties is always at peak, and the daily caloric intake is often quite astonishing. At the risk of playing the role of Scrooge, this seems a pretty good time to take stock of our approach to food and alcohol consumption, thus giving ourselves a week to frame a realistic and beneficial set of New Year’s resolutions.
The problem of obesity
We know that we are facing an international epidemic of obesity.
It is estimated in AACR Cancer Progress Report 2017 that, by 2025, there will be 91 million obese children globally. Around one-third of our population is now considered to be overweight or obese, a 20% increase since the 1980s.
The AACR document, as well as data from the International Agency for Research on Cancer and the World Cancer Research Fund, have identified at least 14 types of cancer with causative associations linked to obesity — specifically esophageal adenocarcinoma; meningioma; multiple myeloma; and cancers of the prostate, colorectum, endometrium, gallbladder, kidney, liver, ovary, pancreas, stomach, thyroid and postmenopausal breast.
In a study published in July in JAMA, Zheng and colleagues showed that weight gain of only 2.5 kg or more in the age range of 18 to 55 years is associated with an increase in obesity-associated cancers — and other medical conditions — later in life.
There also are well-documented associations between diabetes and cancer, but Pearson-Stuttard and colleagues reported last month in The Lancet Diabetes & Endocrinology that a high BMI (> 25 kg/m2) is responsible for twice as many cancer cases as diabetes. In fact, they have claimed that nearly 800,000 new cases of cancer world-wide (around 5% of the total) in 2012 were caused by diabetes and/or obesity.
The most prominent culprits appear to be energy-dense foods — namely those high in fats and/or added sugars, as well as low in fiber — classically found in fast-food diets. The so-called “healthy diets” dominated by vegetables, fruits and whole grains seem not to be associated with cancer, and may actually have a protective effect.
In parallel, ASCO’s statement on alcohol consumption and cancer risk has cited, in association with any alcohol consumption, an increased relative risk for developing cancers of oropharynx and larynx, esophageal squamous carcinoma, liver, female breast and colo-rectum. These associations are independent of the well-established connection between cigarette and alcohol consumption, although relative risk is worsened when both risk factors are in play.
As the development and causes of both obesity and cancer are multifactorial, it is unlikely that there is a single unifying mechanism to explain the association. However, possible factors that link obesity and carcinogenesis include hyperinsulinism or the impact of the interaction between insulin-like growth factors and their receptors, chronic inflammation, and a broad range of hormonal triggers, particularly for female breast cancer. Chronic obesity is associated with an increase in circulating biomarkers of inflammation, such as C-reactive protein.
Sadly, the correlation between obesity and cancer is yet another example of disparities of care within the United States and beyond, as there are strong data to show that obesity-related cancers occur with disproportionately high frequency among the less educated and lower socioeconomic communities — mostly because high-density foods tend to be less expensive. Chronic alcoholism also is associated with lower socioeconomic status, compounded by a paucity of social support mechanisms — a situation that is likely to deteriorate in the current political climate.
Reducing risk
There is a general de facto consensus that there are many benefits from a healthy diet, weight loss, reduction of alcohol intake and increased levels of exercise.
In the present context, many sensible steps that can be taken potentially to help reduce the risk for suffering obesity-associated cancers include:
- Portion control, with an absolute reduction of caloric intake;
- Increased physical activity to more than 30 minutes daily — this can translate into measuring steps with a target in excess of 10,000 to 15,000 steps per day;
- Reduction of consumption of energy-dense foods;
- Increased consumption of vegetables, fruits, whole grains and beans, which have lower energy density;
- Reduction of intake of red meat/processed meats; and
- Reduction of alcohol consumption.
To be honest, the extent to which these steps will reduce the risk for cancer is not completely clear.
Eliasson and colleagues have reported that postmenopausal women with a sustained weight reduction of 10 kg or more will have a 50% reduction in the risk for developing breast cancer.
It may be that the reduction of circulating estrogens associated with postmenopausal weight loss is the basis for the reduction in cancer incidence. Adams and colleagues have reported, among others, that weight reduction or bariatric surgery is associated with a reduced incidence of colon cancer, with a greater effect among men. There are many anecdotal reports and case-control studies that support the efficacy of weight loss in cancer reduction in many different malignancies, and it is possible that the aggression of some obesity-related cancers, such as prostate malignancy, can be reduced somewhat by dietary intervention.
The bottom line is simple. Obesity is an international epidemic, with adverse health effects that rival those of tobacco use. Analogous to the use of tobacco, there are many simple steps that can potentially reduce the risks for obesity-associated cardiovascular disease, diabetes and cancer.
The real key is to capture the attention of the community at large — and of government in particular — to start the process of changing patterns of behavior that cause short-term satisfaction at the expense of long-term catastrophe. Our best shot at making a real difference is in addressing this problem in our children.
References:
AACR Cancer Progress Report 2017: Harnessing Research Discoveries to Save Lives. Available at: cancerprogressreport.org/Pages/cpr17-contents.aspx. Accessed on Dec. 1, 2017.
Adams TD, et al. N Engl J Med. 2007;357:753-761.
Eliasson AH, et al. JAMA. 2006;296:193-201.
Pearson-Stuttard J, et al. Lancet Diabetes Endocrinol. 2017;doi:10.1016/S2213-8587(17)30366-2.
Zheng Y, et al. JAMA. 2017;doi:10.1001/jama.2017.7092.
For more information:
Derek Raghavan, MD, PhD, FACP, FRACP, FASCO, is HemOnc Today’s Chief Medical Editor for Oncology. He also is president of Levine Cancer Institute at Carolinas HealthCare System. He can be reached at derek.raghavan@carolinashealthcare.org.
Disclosure: Raghavan reports no relevant financial disclosures.