Obesity and cancer: An update of the global impact

Highlights

• The prevalence of obesity is increasing and only in a few countries it starts to flatten.

• As a consequence of the global rise of obesity, the current and the future burden of cancers related to obesity are rising.

• Not only affecting the occurrence of cancer, the increasing prevalence of obesity also affects prognosis among cancer survivors.

• The prevention of the obesity pandemic is complex and requires a locally tailored approach to reduce harms on cancers and other diseases.

Abstract

In view of the growing global obesity epidemic, this paper reviews the relation between recent trends in body mass index (BMI) and the changing profile of cancer worldwide. By examining seven selected countries, each representing a world region, a pattern of increasing BMI with region and gender-specific diversity is noted: increasing levels of BMI were most pronounced in the Middle East (Saudi Arabia), rather modest in Eastern Asia (India) and generally more rapid in females than in males. This observation translates into a disproportionate distribution of cancer attributable to high levels of BMI, ranging by sex from 4–9% in Saudi Arabia and from 0.2–1.2% in India. Overweight and obesity may also influence cancer outcomes, and hence have a varying impact on cancer survival and death in different world regions. Future challenges in cancer studies exploring the association with overweight and obesity concern the measurement of adiposity and its potentially cumulative effect over the life course. Given the limitations of BMI as an imperfect measure of body fatness, routine anthropometric data collection needs to be extended to develop more informative measures, such as waist circumference in settings where the gold standard tools remain unaffordable. Furthermore, questions surrounding the dose-response and timing of obesity and their associations with cancer remain to be answered. Improved surveillance of health risk factors including obesity as well as the scale and profile of cancer in every country of the world is urgently needed. This will enable the design of cost-effective actions to curb the growing burden of cancer related to excess body weight.

Introduction

The global prevalence of overweight and obesity (body mass index (BMI) ≥25 kg/m²) has increased markedly over the past decades from 24.6% in 1980, to 34.4% in 2008. Over the same period, the prevalence of obesity (BMI ≥30 kg/m²) has doubled, from 6.4% to 12.0% [1]. In many countries these changes have impacted on the main non-communicable diseases including heart disease [2], type 2 diabetes [2], as well as cancer [3], [4], [5]. Excess body weight has been causally linked to an increased risk of ten different cancer types, including cancer of the oesophagus (adenocarcinoma), colorectum, gallbladder, pancreas, liver, breast (post-menopausal), ovary, endometrium, kidney and prostate (advanced stage) [3], [6], [7], [8], [9], [10], [11], [12], [13]. These cancers alone (described hereafter as obesity-related cancers) comprise about 27% of the total global burden of cancer (based on GLOBOCAN 2012 data [14] and at present impact more on populations in highly-developed countries, where 67% of all obesity-related cancers are diagnosed. This observation is further confirmed by a recent study showing that 82% of all new cancer cases caused by excess body weight in 2012 were found in high income countries, as compared to only 18% in their lesser income counterparts [15].

Transitions in global cancer patterns have also been observed and have partly been linked to the growing obesity epidemic [16]. One example is the changing trends in oesophageal adenocarcinoma, a subtype of oesophageal cancer that is strongly associated with excess weight, with obesity increasing risk by greater than two-fold compared with normal weight [17]. Since the early-1990s, studies from high income countries such as the U.S. have noted a steep rise in the incidence of oesophageal adenocarcinoma, surpassing the incidence of oesophageal squamous cell carcinoma, which is related mainly to tobacco smoking [18]. At the global level, oesophageal adenocarcinoma now contributes 25% of the total oesophageal cancer burden in highly developed countries, in contrast to 6% in less developed countries [19].

In this paper, we provide an overview of the impact of overweight and obesity on the global burden of cancer. We link geographical and temporal patterns of BMI to the corresponding scale and profile of cancer, and quantify the number of new cancer cases attributable to high BMI in countries representing seven world regions. The challenges in surveillance of body composition in ethnically diverse populations are briefly summarized, and future research avenues on this basis discussed. We conclude with a perspective on specific actions required to curb the growing burden of cancers related to excess body weight, with a focus on locally-tailored strategies.