ReviewThe Counterweight programme: Prevalence of CVD risk factors by body mass index and the impact of 10% weight change
Introduction
The World Health Organisation (WHO) has recognized a global epidemic of obesity [1]. The prevalence of obesity in the United Kingdom (UK) is 23.6% men and 23.8% women in England [2] and, 22.4% and 26%, respectively in Scotland [3]. Prediction of trends of obesity in England suggests 26% men and 28% women will be clinically obese by 2010, imposing a great burden on healthcare resources [4].
The Counterweight programme was developed to examine the current approaches to obesity management in UK primary care, and to develop an evidence-based model for the management of this chronic disease. Interventions in primary care currently target high-risk individuals with existing obesity-related conditions [5]; the mean BMI of patients recruited for weight management in primary care was 37 and 75% had at least one pre-existing obesity-related disease [6]. A 10% weight loss has been associated with clinically meaningful reductions in hypertension, lipids and mortality risk [7]. There is however little evidence published as to the reduction in risk of developing an obesity-related disease with this weight loss target.
The prevalence of obesity-related pathology rises with increasing BMI [8], [9], [10]. The risk of developing type 2 DM doubles at BMI 23 to <25 kg/m2 compared to BMI < 23 kg/m2, increasing exponentially to around 40-fold at BMI > 35 kg/m2 [11]. Hypertension prevalence rises progressively with increasing BMI, more at younger ages and less after age 60 years [8]. The prevalence of hypercholesterolaemia increases at BMI > 25 kg/m2 compared to BMI 18.5 to <25 kg/m2. High density lipoprotein (HDL) cholesterol levels fall as BMI increases, particularly under age 60 years [1], [8]. Coronary heart disease (CHD) prevalence increases progressively with BMI > 22 kg/m2 [11], [12], and the effect of weight on CHD mortality are partly independent of traditional risk factors [13].
Obesity-related disease increases within the normal weight range [11], [12], while increased risks have been documented in obese patients (BMI ≥ 30 kg/m2) compared to normal weight (BMI 18.5 to <25 kg/m2) little work has examined the progressive effects of intermediate increments of BMI ≥ 25 kg/m2. Such studies are particularly important with the rising prevalence of overweight and obesity, to inform governments and healthcare financiers of the likely health economic costs of this epidemic and to allow resource targeting. The general population trend is for weight gain throughout our lifespan [14], with a consistent increase in the number of overweight and obese individuals [7]. This raises questions about the critical point in the natural history of weight gain for intervention, to maximize the prevention of obesity-related co-morbidities.
This paper firstly examines the relationship between grades of overweight/obesity and the prevalence of physician-recorded cardiovascular co-morbidities in primary care, and identifies BMI thresholds associated with the greatest health risk. Secondly, the theoretical effects on disease risk of a 10% weight loss or gain are examined.
Section snippets
Methods
The Counterweight Project developed and tested a weight management intervention programme in primary care, incorporating a large cross-sectional analysis of obese, overweight and normal weight patients (Table 1). The Counterweight Programme was approved by the West Midlands Multi-Centre Research Ethics Committee (MREC) and subsequently by Local Research Ethics Committees (LREC) in each region. Project methodology is published in detail elsewhere [15].
Procedures
Invitation letters were sent offering assistance in establishing a structured approach to weight management within existing resources; eighty general practices from seven UK centres were willing to be involved in obtaining data on obesity-related diseases in their practices. The Counterweight practices show variations in size, geographical location and socio-economic deprivation, and are broadly representative of UK general practices (Table 2).
A subset of 6150 obese patients was sampled using a
Statistical analysis
Data were analysed in SPSS 13.0 using logistic regression to obtain OR for each obesity-related co-morbidity in relation to the normal weight BMI band (18.5 to <25 kg/m2). Adjustment was made for sex, age, country of residence (Scotland or England), and practice socio-economic deprivation category. Males and females were analysed separately, as were age groups. BMI trend was assessed by fitting the models again, but replacing BMI band with continuous linear and quadratic variables.
To assess the
Results
Of the 6150 obese patients, 70% had grade I obesity (BMI 30 to <35 kg/m2) and 10% grade III obesity (BMI ≥ 40 kg/m2). Of the 1150 overweight patients, 60% had a BMI 25 to <27.5 kg/m2. One third of the normal and overweight patients, and 41% of obese were current smokers (Table 3). Results are presented as a summary of the OR of having an obesity-related co-morbidity as BMI increases using BMI bands, and then a modelling of the change in risk with 10% weight loss/gain.
Prevalence of type 2 DM rises
Discussion
Increasing weight has major impact on many chronic diseases, with significantly increased risks for type 2 DM, hypertension, dyslipidaemia and CHD in both sexes.
We demonstrate a significant curvilinear link between increasing weight and prevalence of type 2 DM, although we did not see the continued increase at BMI ≥ 35 seen by others [9], [11], [16]. These findings may reflect the under-diagnosis of, and lack of formal testing for, type 2 DM in the obese in UK primary care [17]. There is an
Conclusion
This study confirms the central role of obesity in CV and metabolic disease risk with significant increases in the prevalence of type 2 DM, hypertension, dyslipidaemia, CVD and CHD with increasing BMI. In the UK, little is known about current management practices for obesity in the primary care setting [5] and many resources are spent on the treatment of obesity-related co-morbidities [7]. The substantial reduction in risk of developing CVD risk factors associated with modest weight loss,
Acknowledgements
Roche Products Ltd. provided a six-year educational grant-in-aid to the Counterweight Project Board and to The Robert Gordon University, Aberdeen. The programme was designed and run by the Counterweight Project Team independent of Roche Products Ltd. We are grateful to the participating practices for their enthusiasm and cooperation and to all the patients who participated. Thanks go to Professor A. Barnett and Professor J. Wilding who participated in the initial discussions in the development
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