Cancer prevention through weight control-where are we in 2020?

Abstract

Growing data from epidemiological studies highlight the association between excess body fat and cancer incidence, but good indicative evidence demonstrates that intentional weight loss, as well as increasing physical activity, offers much promise as a cost-effective approach for reducing the cancer burden. However, clear gaps remain in our understanding of how changes in body fat or levels of physical activity are mechanistically linked to cancer, and the magnitude of their impact on cancer risk. It is important to investigate the causal link between programmes that successfully achieve short-term modest weight loss followed by weight-loss maintenance and cancer incidence. The longer-term impact of weight loss and duration of overweight and obesity on risk reduction also need to be fully considered in trial design. These gaps in knowledge need to be urgently addressed to expedite the development and implementation of future cancer-control strategies. Comprehensive approaches to trial design, Mendelian randomisation studies and data-linkage opportunities offer real possibilities to tackle current research gaps. In this paper, we set out the case for why non-pharmacological weight-management trials are urgently needed to support cancer-risk reduction and help control the growing global burden of cancer.

Fig. 1. Expected effects of lowering BMI on cancer risk—how Mendelian Randomisation can guide research.

Current estimates from genetically informed Mendelian randomisation (MR) studies can be used to set expectations for the results of future randomised controlled trials. A recent meta-analysed MR estimate of BMI for colorectal cancer (from Jarvis et al.) suggests that a 5 kg/m² lower BMI would reduce the risk of developing colorectal cancer by ~20%. This MR estimate reflects lifetime exposure to this relatively lower BMI, and so the magnitude of reduced colorectal cancer risk in response to short-term BMI reduction is expected to differ.