Obesity and alcohol consumption are both important modifiable risk factors for cancer. We examined the joint association of adiposity and alcohol consumption with alcohol- and obesity-related cancer incidence. This prospective cohort study included cancer-free UK Biobank participants aged 40–69 years. Alcohol consumption was categorised based on current UK guidelines into four groups. We defined three markers of adiposity: body fat percentage (BF %), waist circumference and BMI and categorised each into three groups. We derived a joint alcohol consumption and adiposity marker variable with twelve mutually exclusive categories. Among 399 575 participants, 17 617 developed alcohol-related cancer and 20 214 developed obesity-related cancer over an average follow-up of 11·8 (SD 0·9) years. We found relatively weak evidence of independent associations of alcohol consumption with cancer outcomes. However, the joint association analyses showed that across all adiposity markers, above guideline drinkers who were in the top two adiposity groups had elevated cancer incidence risk (e.g. HR for alcohol-related cancer was 1·53 (95 % CI (1·24, 1·90)) for within guideline drinkers and 1·61 (95 % CI (1·30, 2·00)) for above guideline drinkers among participants who were in the top tertile BF %. Regardless of alcohol consumption status, the risk of obesity-related cancer increased with higher adiposity in a dose–response manner within alcohol consumption categories. Our study provides guidance for public health priorities aimed at lowering population cancer risk via two key modifiable risk factors.

The objective of this cross-sectional study was to clarify the association between alcohol and obesity using data from 106 182 adults in England and Scotland (46·7 % male; mean 46·9 (sd 16·9) years). Trained interviewers asked participants about alcohol intake. Obesity was defined as BMI≥30 kg/m2. Potential confounders included age, sex, smoking, physical activity, longstanding illness, psychological distress and socioeconomic status. Compared with those who drank at least five times a week, obesity risk was 1·21 (95 % CI 1·15, 1·27) in those who drank one to four times a week, 1·53 (95 % CI 1·43, 1·62) in those who drank one to two times a month, 1·61 (95 % CI 1·52, 1·71) in those who drank less than once every couple of months, 1·34 (95 % CI 1·23, 1·47) in those who were former drinkers, and 1·03 (95 % CI 0·95, 1·11) in those who were never drinkers. Compared with those who drank a harmful volume, obesity risk was 0·78 (95 % CI 0·68, 0·90) in those who drank within guidelines, 0·69 (95 % CI 0·54, 0·88) in former drinkers and 0·50 (95 % CI 0·40, 0·63) in never drinkers; and, these associations were biased away from the null after adjustment for drinking volume. Abstinence was associated with increased risk of obesity in women. These data suggest that the association between drinking frequency and obesity is bell-shaped, with obesity risk not significantly different in those who drink most often and never drinkers. Drinking volume has a positive confounding effect on the association between drinking frequency and obesity, which may help explain the conflicting findings of other studies.

Physical inactivity is an important risk factor for many chronic diseases and contributes to obesity and poor mental well-being. The present paper describes the main advantages and disadvantages, practical problems, suggested uses, and future developments regarding self-reported and objective data collection in the context of dietary surveys. In dietary surveys, physical activity is measured primarily to estimate energy expenditure. Energy expenditure surveillance is important for tracking changes over time, particularly given the debates over the role of the relative importance of energy intake and expenditure changes in the aetiology of obesity. It is also important to assess the extent of underreporting of dietary intake in these surveys. Physical activity data collected should include details on the frequency, duration and relative intensity of activity for each activity type that contributes considerably to overall activity and energy expenditure. Problems of validity and reliability, associated with inaccurate assessment, recall bias, and social desirability bias, are well-known; children under 10 years cannot report their activities accurately. However, despite such limitations, questionnaires are still the dominant method of physical activity assessment in dietary surveys due to their low cost and relatively low participant burden. Objective, time-stamped measures that monitor heart rate and/or movement can provide more comprehensive, quantitative assessment of physical activity but at greater cost and participant burden. Although overcoming many limitations of questionnaires, objective measures also have drawbacks, including technical, practical and interpretational issues.

The aim of the present study was to investigate the relationships of physical activity types and sedentary behaviour with BMI and waist circumference (WC). The sample comprised 6215 adults (2775 men, 3440 women) aged 16 years and over living in Scotland. Self-reported physical activity of moderate to vigorous intensity (MVIA) included domestic activity, walking, and sports and exercises. MVIA levels were classified as being inactive, being insufficiently active, being sufficiently active for general health benefits and being sufficiently active for obesity prevention. Sedentary time was defined as television and other screen-based entertainment time (TVSE). Dependent variables were BMI-defined obesity (BMI-OB) and WC-defined obesity (WC-OB). TVSE was positively related to both WC-OB (adjusted OR 1·69 (95 % CI 1·39, 2·05) for ≥ 4 h of TVSE per d compared with < 2 h/d) and BMI-OB (OR 1·88; 95 % CI 1·51, 2·35) independently of MVIA. Those classified as most active who reported ≥ 4 h/d of TVSE had higher prevalence of BMI-OB (18·9 v. 8·3 %; P < 0·05) and WC-OB (28·0 v. 10·0 %; P < 0·01) than those equally active with < 2 h/d of TVSE. Sports and walking were related inversely to WC-OB (OR for no time compared with ≥ 30 min/d: 1·55 (95 % CI 1·24, 1·94); 2·06 (95 % CI 1·64, 2·58)), but only walking was related to BMI-OB (OR 1·94; 95 % CI 1·58, 2·37). Domestic physical activity was not related to BMI-OB or WC-OB. In conclusion, physical activity and sedentary behaviour are independently related to obesity. Public health recommendations should both promote physical activity and discourage engagement in sedentary pursuits.