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Recent research: five papers on overweight - mortality, cardiovascular risk, diets, and schools

Here are five papers mostly looking at aspects of overweight.  The first, published recently in the Lancet, is a huge study on the effects of body-mass index (BMI) on subsequent mortality in nearly 900,000 adults.  It shows progressive excess mortality above the BMI range 22.5-25 kg/m2.  (To calculate your BMI click here).  At 40-45 kg/m2, the reduction in life expectancy of 8-10 years is comparable to the effects of being a smoker.  The second paper, by Neovius et al, also involved large numbers - over 45,000 older adolescents.  Again it showed excess mortality at long term follow-up, and commented "Obesity and overweight were as hazardous as heavy and light smoking, respectively".  The third study by Katseva et al looked at modifiable risk factors in European patients with cardiac disease.  The findings were depressing with obesity, for example, increasing stepwise from 25% at first survey, to 32.6% at second, to 38% at third survey.  Overall the authors concluded "These time trends show a compelling need for more effective lifestyle management of patients with coronary heart disease ... To salvage the acutely ischaemic myocardium without addressing the underlying causes of the disease is futile; we need to invest in prevention." 

The fourth and fifth papers are about "treatment".  The Sacks et al paper compared weight loss diets.  They wrote "The possible advantage for weight loss of a diet that emphasizes protein, fat, or carbohydrates has not been established, and there are few studies that extend beyond 1 year. Methods: We randomly assigned 811 overweight adults to one of four diets; the targeted percentages of energy derived from fat, protein, and carbohydrates in the four diets were 20, 15, and 65%; 20, 25, and 55%; 40, 15, and 45%; and 40, 25, and 35%." and commented "Among the 80% of participants who completed the trial, the average weight loss was 4 kg; 14 to 15% of the participants had a reduction of at least 10% of their initial body weight. Satiety, hunger, satisfaction with the diet, and attendance at group sessions were similar for all diets; attendance was strongly associated with weight loss (0.2 kg per session attended)." concluding "Reduced-calorie diets result in clinically meaningful weight loss regardless of which macronutrients they emphasize."  In some ways I find the fifth study - by Marcus et al - the most encouraging.  It showed that intervening at a school level can be helpful.  "Ten schools were selected in Stockholm county area and randomized to intervention (n=5) and control (n=5) schools. Low-fat dairy products and whole-grain bread were promoted and all sweets and sweetened drinks were eliminated in intervention schools ... Eating habits at home were assessed by parental report."  At 4 year follow-up, they found "The prevalence of overweight and obesity decreased by 3.2% (from 20.3 to 17.1) in intervention schools compared with an increase of 2.8% (from 16.1 to 18.9) in control schools (P<0.05) ... a larger proportion of the children who were initially overweight reached normal weight in the intervention group (14%) compared with the control group (7.5%), P=0.017 ... Eating habits at home were found to be healthier among families with children in intervention schools at the end of the intervention. There was no difference between children in intervention and control schools in self-reported eating disorders."  This is further work showing the importance of intervening at both individual and social levels in tackling overweight. 

Prospective Studies, C. (2009). "Body-mass index and cause-specific mortality in 900,000 adults: collaborative analyses of 57 prospective studies." The Lancet 373(9669): 1083-1096.  [Abstract/Full Text]
Background:  The main associations of body-mass index (BMI) with overall and cause-specific mortality can best be assessed by long-term prospective follow-up of large numbers of people. The Prospective Studies Collaboration aimed to investigate these associations by sharing data from many studies.  Methods: Collaborative analyses were undertaken of baseline BMI versus mortality in 57 prospective studies with 894,576 participants, mostly in western Europe and North America (61% [n=541,452] male, mean recruitment age 46 [SD 11] years, median recruitment year 1979 [IQR 1975-85], mean BMI 25 [SD 4] kg/m2).  The analyses were adjusted for age, sex, smoking status, and study.  To limit reverse causality, the first 5 years of follow-up were excluded, leaving 66,552 deaths of known cause during a mean of 8 (SD 6) further years of follow-up (mean age at death 67 [SD 10] years): 30,416 vascular; 2070 diabetic, renal or hepatic; 22,592 neoplastic; 3770 respiratory; 7704 other.  Findings: In both sexes, mortality was lowest at about 22.5-25 kg/m2.  Above this range, positive associations were recorded for several specific causes and inverse associations for none, the absolute excess risks for higher BMI and smoking were roughly additive, and each 5 kg/m2 higher BMI was on average associated with about 30% higher overall mortality (hazard ratio per 5 kg/m2 [HR] 1.29 [95% CI 1.27-1.32]): 40% for vascular mortality (HR 1.41 [1.37-1.45]); 60-120% for diabetic, renal, and hepatic mortality (HRs 2.16 [1.89-2.46], 1.59 [1.27-1.99], and 1.82 [1.59-2.09], respectively); 10% for neoplastic mortality (HR 1.10 [1.06-1.15]); and 20% for respiratory and for all other mortality (HRs 1.20 [1.07-1.34] and 1.20 [1.16-1.25], respectively).  Below the range 22.5-25 kg/m2, BMI was associated inversely with overall mortality, mainly because of strong inverse associations with respiratory disease and lung cancer. These inverse associations were much stronger for smokers than for non-smokers, despite cigarette consumption per smoker varying little with BMI.  Interpretation: Although other anthropometric measures (eg, waist circumference, waist-to-hip ratio) could well add extra information to BMI, and BMI to them, BMI is in itself a strong predictor of overall mortality both above and below the apparent optimum of about 22.5-25 kg/m2.  The progressive excess mortality above this range is due mainly to vascular disease and is probably largely causal.  At 30-35 kg/m2, median survival is reduced by 2-4 years; at 40-45 kg/m2, it is reduced by 8-10 years (which is comparable with the effects of smoking).  The definite excess mortality below 22.5 kg/m2 is due mainly to smoking-related diseases, and is not fully explained.

Neovius, M., J. Sundstrom, et al. (2009). "Combined effects of overweight and smoking in late adolescence on subsequent mortality: nationwide cohort study." BMJ 338(feb24_2): b496-.  [Free Full Text]
Objective To investigate the combined effects on adult mortality of overweight and smoking in late adolescence. Design Record linkage study with Cox proportional hazard ratios adjusted for muscle strength, socioeconomic position, and age. Setting Swedish military service conscription register, cause of death register, and census data. Participants 45 920 Swedish men (mean age 18.7, SD 0.5) followed for 38 years. Main outcome measures Body mass index (underweight (BMI <18.5), normal weight (18.5-24.9), overweight (25-29.9), and obesity (>/=30)), muscle strength, and self reported smoking (non-smoker, light smoker (1-10 cigarettes/day), heavy smoker (>10/day)) at mandatory military conscription tests in 1969-70. All cause mortality. Results Over 1.7 million person years, 2897 men died. Compared with normal weight men (incidence rate 17/10 000 person years, 95% confidence interval 16 to 18), risk of mortality was increased in overweight (hazard ratio 1.33, 1.15 to 1.53; incidence rate 23, 20 to 26) and obese men (hazard ratio 2.14, 1.61 to 2.85; incidence rate 38, 27 to 48), with similar relative estimates in separate analyses of smokers and non-smokers. No increased risk was detected in underweight men (hazard ratio 0.97, 0.86 to 1.08; incidence rate 18, 16 to 19), though extreme underweight (BMI <17) was associated with increased mortality (hazard ratio 1.33, 1.07 to 1.64; incidence rate 24, 19 to 29). The relative excess risk due to interaction between BMI and smoking status was not significant in any stratum. Furthermore, all estimates of interaction were of small magnitude, except for the combination of obesity and heavy smoking (relative excess risk 1.5, -0.7 to 3.7). Compared with non-smokers (incidence rate 14, 13 to 15), risk was increased in both light (hazard ratio 1.54, 1.41 to 1.70; incidence rate 15, 14 to 16) and heavy smokers (hazard ratio 2.11, 1.92 to 2.31; incidence rate 26, 24 to 27). Conclusions Regardless of smoking status, overweight and obesity in late adolescence increases the risk of adult mortality. Obesity and overweight were as hazardous as heavy and light smoking, respectively, but there was no interaction between BMI and smoking status. The global obesity epidemic and smoking among adolescents remain important targets for intensified public health initiatives.

Kotseva, K., D. Wood, et al. (2009). "Cardiovascular prevention guidelines in daily practice: a comparison of EUROASPIRE I, II, and III surveys in eight European countries." Lancet 373(9667): 929-40.  [PubMed]
BACKGROUND: The first and second EUROASPIRE surveys showed high rates of modifiable cardiovascular risk factors in patients with coronary heart disease. The third EUROASPIRE survey was done in 2006-07 in 22 countries to see whether preventive cardiology had improved and if the Joint European Societies' recommendations on cardiovascular disease prevention are being followed in clinical practice. METHODS: EUROASPIRE I, II, and III were designed as cross-sectional studies and included the same selected geographical areas and hospitals in the Czech Republic, Finland, France, Germany, Hungary, Italy, the Netherlands, and Slovenia. Consecutive patients (men and women </=70 years) were identified after coronary artery bypass graft or percutaneous coronary intervention, or a hospital admission with acute myocardial infarction or ischaemia, and were interviewed at least 6 months later. FINDINGS: 3180 patients were interviewed in the first survey, 2975 in the second, and 2392 in the third. Overall, the proportion of patients who smoke has remained nearly the same (20.3% in EUROASPIRE I, 21.2% in II, and 18.2% in III; comparison of all surveys p=0.64), but the proportion of women smokers aged less than 50 years has increased. The frequency of obesity (body-mass index >/=30 kg/m(2)) increased from 25.0% in EUROASPIRE I, to 32.6% in II, and 38.0% in III (p=0.0006). The proportion of patients with raised blood pressure (>/=140/90 mm Hg in patients without diabetes or >/=130/80 mm Hg in patients with diabetes) was similar (58.1% in EUROASPIRE I, 58.3% in II, and 60.9% in III; p=0.49), whereas the proportion with raised total cholesterol (>/=4.5 mmol/L) decreased, from 94.5% in EUROASPIRE I to 76.7% in II, and 46.2% in III (p<0.0001). The frequency of self-reported diabetes mellitus increased, from 17.4%, to 20.1%, and 28.0% (p=0.004). INTERPRETATION: These time trends show a compelling need for more effective lifestyle management of patients with coronary heart disease. Despite a substantial increase in antihypertensive and lipid-lowering drugs, blood pressure management remained unchanged, and almost half of all patients remain above the recommended lipid targets. To salvage the acutely ischaemic myocardium without addressing the underlying causes of the disease is futile; we need to invest in prevention.

Sacks, F. M., G. A. Bray, et al. (2009). "Comparison of Weight-Loss Diets with Different Compositions of Fat, Protein, and Carbohydrates." N Engl J Med 360(9): 859-873.  [Abstract/Full Text]
Background The possible advantage for weight loss of a diet that emphasizes protein, fat, or carbohydrates has not been established, and there are few studies that extend beyond 1 year. Methods We randomly assigned 811 overweight adults to one of four diets; the targeted percentages of energy derived from fat, protein, and carbohydrates in the four diets were 20, 15, and 65%; 20, 25, and 55%; 40, 15, and 45%; and 40, 25, and 35%. The diets consisted of similar foods and met guidelines for cardiovascular health. The participants were offered group and individual instructional sessions for 2 years. The primary outcome was the change in body weight after 2 years in two-by-two factorial comparisons of low fat versus high fat and average protein versus high protein and in the comparison of highest and lowest carbohydrate content. Results At 6 months, participants assigned to each diet had lost an average of 6 kg, which represented 7% of their initial weight; they began to regain weight after 12 months. By 2 years, weight loss remained similar in those who were assigned to a diet with 15% protein and those assigned to a diet with 25% protein (3.0 and 3.6 kg, respectively); in those assigned to a diet with 20% fat and those assigned to a diet with 40% fat (3.3 kg for both groups); and in those assigned to a diet with 65% carbohydrates and those assigned to a diet with 35% carbohydrates (2.9 and 3.4 kg, respectively) (P>0.20 for all comparisons). Among the 80% of participants who completed the trial, the average weight loss was 4 kg; 14 to 15% of the participants had a reduction of at least 10% of their initial body weight. Satiety, hunger, satisfaction with the diet, and attendance at group sessions were similar for all diets; attendance was strongly associated with weight loss (0.2 kg per session attended). The diets improved lipid-related risk factors and fasting insulin levels. Conclusions Reduced-calorie diets result in clinically meaningful weight loss regardless of which macronutrients they emphasize.

Marcus, C., G. Nyberg, et al. (2009). "A 4-year, cluster-randomized, controlled childhood obesity prevention study: STOPP." Int J Obes.  [Abstract/Full Text]
Objective: To assess the efficacy of a school-based intervention programme to reduce the prevalence of overweight in 6 to 10-year-old children.  Design: Cluster-randomized, controlled study.  Subjects: A total of 3135 boys and girls in grades 1-4 were included in the study.  Methods: Ten schools were selected in Stockholm county area and randomized to intervention (n=5) and control (n=5) schools. Low-fat dairy products and whole-grain bread were promoted and all sweets and sweetened drinks were eliminated in intervention schools. Physical activity (PA) was aimed to increase by 30 min day-1 during school time and sedentary behaviour restricted during after school care time. PA was measured by accelerometry. Eating habits at home were assessed by parental report. Eating disorders were evaluated by self-report.  Results: The prevalence of overweight and obesity decreased by 3.2% (from 20.3 to 17.1) in intervention schools compared with an increase of 2.8% (from 16.1 to 18.9) in control schools (P<0.05). The results showed no difference between intervention and controls, after cluster adjustment, in the longitudinal analysis of BMIsds changes. However, a larger proportion of the children who were initially overweight reached normal weight in the intervention group (14%) compared with the control group (7.5%), P=0.017. PA did not differ between intervention and control schools after cluster adjustment. Eating habits at home were found to be healthier among families with children in intervention schools at the end of the intervention. There was no difference between children in intervention and control schools in self-reported eating disorders.  Conclusions: A school-based intervention can reduce the prevalence of overweight and obesity in 6 to 10-year-old children and may affect eating habits at home. The effect of the intervention was possibly due to its effect on healthy eating habits at school and at home rather than on increased levels of PA.

 

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