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Let us not ignore body weight gain (by Annie S. Anderson)

Professor Annie S. Anderson
Centre for Research in Cancer Prevention and Screening, Ninewells Medical School, University of Dundee

It is predicted that global obesity will reach 18% in men and over 21% in women by 2025 (1).  Obesity is associated with the development of diabetes, cardiovascular disease and 11 cancers including breast and bowel cancer (2).  Globally, and especially in the developing world, no country can afford the increasing cost of surgical, medical and oncological treatments.  Prevention must be part of the solution to decrease Non Communicable Diseases and that includes obesity prevention.
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(ISBNPA and Annie Anderson thanks Marion Lean for the picture)

Food, drink, activity and inactivity are four key partners in the development and solutions of our obesity epidemic.  All ISBNPA researchers who work in these fields should at some stage consider body size in their work – because excess body fat will impact on measurements, intervention (design, eligibility and response) and health planning.  In academic public health circles there have been some interesting debates on whether overweight is really as big a health problem as some suspect and research continues to pursue the concept of being metabolically fit rather than worry about fat. While such arguments will fuel debates for a long time they may cloud the basic messages and actions that address the following
a) increasing physical activity is an important health behaviour (at whatever size) 
b) the impact of increasing activity on body weight is most effective when combined with appropriate dietary measures (3) 
c) If we fail to measure body size then we are ignoring  the creep of weight gain that leads to first to overweight and onwards towards obesity
No-one is born obese. We can produce many figures on weight categories by age group and we know that obese children and adolescents are 5 times more likely to become obese adults (4). We can describe weight gain in adult life using excellent cohort studies such as the EPIC study which has reported an increase of around 400g per annum (5) and we can model body weight trajectories based on a few simple measurement points.
I wonder whether we should re-think our measurements. The important warning signs of weight gain in adult life are virtually ignored and surely continuous monitoring must be part of the armoury of obesity prevention.  In  life stages where weight gain is crucial (pregnancy, infancy and childhood) good monitoring  processes are in place such as WHO infant growth charts (6) but beyond these critical points we seem to turn a blind eye and wait till a magic BMI cut point (overweight or obesity) is reached. 
Weight gain may also be of particular concern in the development of cancer, notably post-menopausal breast cancer. Numerous studies have highlighted weight gain as a risk factor (Independent of body weight status) for this disease including kg gained after the age of 50 years (7,8). BMI is, of course, a proxy for body fat storage and although not ideal provides a useful practical clinical guide. Noting an increase in dress size or trouser measurements might be even more useful (9) because these measures need no technical equipment (even with the inconsistency of differing sizes within the retail sector). When was the last time you asked someone if they can still get in to their wedding outfit bought ten years earlier? 
So my hope is that public health efforts in obesity can be extended beyond debate on the merits of physical activity and diet to a focus on raising awareness of unintentional weight gain, setting goals for maximum annual weight gain and facilitating help and guidance when waistbands begin to increase irrespective of starting size.
References
1. NCD Risk Factor Collaboration (NCD-RisC) (2016).  Trends in adult body-mass index in 200 countries from 1975 to 2014: a pooled analysis of 1698 population-based measurement studies with 19·2 million participants.  Lancet Apr 2;387(10026):1377-96
3. Foster-Schubert KE, Alfano CM, Duggan CR et al (2012).  Effect of diet and exercise, alone or combined, on weight and body composition in overweight-to-obese postmenopausal women.  Obesity (Silver Spring) Aug;20(8):1628-38. doi: 10.1038/oby.2011.76. Epub 2011 Apr 14.  
4. Simmonds M, Llewellyn A, Owen CG, Woolacott N (2016).  Predicting adult obesity from childhood obesity: a systematic review and meta-analysis. Obes Rev. Feb;17(2):95-107. doi: 10.1111/obr.12334. Epub 2015 Dec 23.
5. Romaguera D, Norat T, Vergnaud AC (2010).  Mediterranean dietary patterns and prospective weight change in participants of the EPIC-PANACEA project.  Am J Clin Nutr. Oct;92(4):912-21. doi: 10.3945/ajcn.2010.29482. Epub 2010 Sep 1
6. Department of Health (2009).  Using the new UK–World Health Organization 0–4 years growth charts. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/215564/dh_127422.pdf
7. Eliassen AH, et al (2006).  Adult weight change and risk of postmenopuasal breast cancer.  JAMA. Jul 12;296(2):193-201
8. Ahn J, Schatzkin A, Lacey Jr JV, et al (2007). Adiposity, adult weight change, and postmenopausal breast cancer risk. Arch Intern Med. Oct 22;167(19):2091-102.
9. Fourkala EO, Burnell M, Cox C et al (2014).  Association of skirt size and postmenopausal breast cancer risk in older women: a cohort study within the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS). BMJ Open Sep 24;4(9):e005400. doi: 10.1136/bmjopen-2014-005400.
Professor Annie S. Anderson
Centre for Research in Cancer Prevention and Screening, Ninewells Medical School, University of Dundee