Study protocol for BeWEL: the impact of a body weight and physical activity intervention on adults who have had a colorectal adenoma

Colorectal cancer (CRC) is the third most commonly diagnosed cancer and the second highest cause of cancer death in the UK. Most cases occur in people over 50 years and CRC often co-exists with other lifestyle related disorders including obesity, type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). These diseases share risk factors related to the metabolic syndrome including large body size, abnormal lipids and markers of insulin resistance indicating common aetiological pathways. This 3 year study will be a two-arm, multicentre, randomised controlled trial comparing the BeWEL lifestyle (diet, physical activity and behaviour change) programme against usual care. The pre-trial development will take 6 months and participants will be recruited over a 12 month period and undertake the intervention and follow up for 12 months (total 24 months recruitment and intervention implementation) with a further 6 months for data collection, analysis and interpretation. Four hundred and fifty two participants who have had a colorectal adenoma detected and removed (through the national colorectal screening programme) will provide 80% power to detect a weight loss of 7% over 12 months. Primary outcomes are changes in body weight and waist circumference. Secondary outcomes will include cardiovascular risk factors, psycho-social measures and intervention costs. The results from this study will enhance the evidence base for lifestyle change in patients at higher risk of chronic disease including obesity related cancers