Weight loss and risk reduction of obesity-related outcomes in 0.5 million people: evidence from a UK primary care database

Abstract

High body mass index (BMI) is known to be associated with various conditions, including type 2 diabetes (T2D), osteoarthritis, cardiovascular disease (CVD) and sleep apnoea; however, the impact of intentional weight loss on the risk of these and other outcomes is not well quantified. We examined the effect of weight loss on ten selected outcomes in a population from the UK Clinical Practice Research Datalink (CPRD) GOLD database. Included individuals were >18 years old at the index date (first BMI value between January 2001 and December 2010). They were categorised by their weight pattern between year 1 post-index and year 4 post-index (baseline period) as having stable weight (-5% to +5%) or weight loss (-25% to -10%, plus evidence of intervention or dietary advice to confirm intention to lose weight). For inclusion, individuals also required a BMI of 25.0-50.0 kg/m² at the start of the follow-up period, during which the occurrence of ten obesity-related outcomes was recorded. Cox proportional hazard models adjusted for BMI, comorbidities, age, sex and smoking status were used to estimate relative risks for weight loss compared with stable weight. Individuals in the weight-loss cohort had median 13% weight loss. Assuming a BMI of 40 kg/m² before weight loss, this resulted in risk reductions for T2D (41%), sleep apnoea (40%), hypertension (22%), dyslipidaemia (19%) and asthma (18%). Furthermore, weight loss was associated with additional benefits, with lower risk of T2D, chronic kidney disease, hypertension and dyslipidaemia compared with maintaining the corresponding stable lower BMI throughout the study. This study provides objective, real-world quantification of the effects of weight loss on selected outcomes, with the greatest benefits observed for the established CVD risk factors T2D, hypertension and dyslipidaemia.

Fig. 1. Study design and objectives.

a Study design showing weight trajectories for the stable-weight (−5% to +5% BMI; orange), weight-loss cohorts (−25% to −10% BMI; blue) and corresponding stable lower BMI (grey). b Illustration of the comparisons made as part of objective 1 and objective 2 at the end of the follow-up period. c Example hazard ratio profiles (HRs and 95% CI) showing the comparative benefit patterns before weight loss (orange) with the risk after weight loss (blue) relative to the corresponding stable lower BMI (grey). ^aRecord indicating either a weight-loss diet, weight-loss drug prescription, or referral to a dietician or for bariatric surgery during the baseline period, to confirm the intention to lose weight; ^bDate of first BMI calculation. BMI body mass index, CI confidence interval, CKD chronic kidney disease, HR hazard ratio, MI myocardial infarction, T2D type 2 diabetes.

Fig. 2. Prevalence of baseline comorbidities.

Bar chart showing the prevalence of comorbidities at baseline (i.e., the start of the follow-up period) in the stable-weight and weight-loss cohorts. CKD chronic kidney disease, CV cardiovascular, T2D type 2 diabetes.

Fig. 3. Risk profiles before and after weight loss for ten obesity-related outcomes (objective 1).

Risk profiles and 95% CI (shaded area) showing the risk of outcomes before (dashed line) and after (solid line) weight loss. HRs are expressed relative to a stable BMI of 30 kg/m². BMI body mass index, CI confidence interval, CKD chronic kidney disease, HR hazard ratio, MI myocardial infarction, T2D type 2 diabetes.

Fig. 4. Risk profile for median 13% weight loss for ten obesity-related outcomes (objective 2).

Changes in outcome risks are plotted as the risk before (orange open circles) and after (blue closed circles) weight loss relative to the corresponding stable lower BMI (grey squares) for each BMI profile. BMI body mass index, CKD chronic kidney disease, HR hazard ratio, MI myocardial infarction, T2D type 2 diabetes.