Evidence-based medicine

-Evidence-based medicine reports on obesity surgery: a critique
H J Sugerman1 and J G Kral2
1. 1Virginia Commonwealth University, Richmond, VA, USA
2. 2SUNY Downstate Medical Center, Brooklyn, NY, USA
Correspondence: Dr HJ Sugerman, 290 Southwinds Drive, Sanibel, FL 33957, USA. E-mail: hsugerman@comcast.net; JG Kral, SUNY Health Science Center, 450 Clarkson Avenue, Box 40, Brooklyn, NY 11203-2098, USA. E-mail: jkral@downstate.edu
Received 29 March 2004; Revised 17 October 2004; Accepted 4 November 2004; Published online 3 May 2005.
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Abstract
OBJECTIVE:

To evaluate evidence in recent authoritative 'Evidence-Based Medicine' (EBM) reports on surgery for severe obesity.
METHODS:

Focused review of Index Medicus citations and authors' own databases of publications on surgery for obesity, 1978–2004.
RESULTS:

EBM criteria for assessment of strength of evidence requiring randomized controlled studies (RCTs) in these reports are inappropriate for evaluating invasive treatments such as surgery, which have robust physiological effects, are difficult to reverse and may have more serious side effects than the drug studies for which the criteria were promulgated. Flaws in these reports include omissions of important studies demonstrating improvements in comorbidity, factual errors in descriptions of operations and faulty analyses of outcomes of laparoscopic approaches. There are misinterpretations of cited papers, and inclusion of obsolete operations as well as a study generated during the 'learning curve' of an avowed complex procedure.
CONCLUSION:

EBM analyses of surgical modalities affecting access to care require relevant evaluation criteria, true peer review and expert consultation. Authors' claims of objectivity by invoking use of evidence-based criteria applicable to drug treatment and other easily reversible forms of therapy are questionable. Decisions based on flawed EBM reports may adversely affect access to care for millions of severely obese patients.
Keywords:
obesity comorbidity, laparoscopic, gastric band, biliopancreatic diversion, duodenal switch, gastric bypass
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-Diagnosis and Treatment of Obesity in Adults: An Applied Evidence-Based Review
A. John Orzano, MD, MPH; John G. Scott, MD, PhD
Authors and Disclosures
Posted: 09/29/2004; J Am Board Fam Med. 2004;17(5) © 2004 American Board of Family Medicine
Abstract and Introduction
Abstract
Background: Obesity is epidemic and leads to substantial morbidity/mortality. Effective strategies exist for managing obesity yet are rarely used by physicians. This applied evidence-based review provides a rationale for the diagnosis and treatment of obesity in adults by providing test characteristics for the body mass index (BMI) and number needed to treat (NNT) for relevant treatments.
Methods: We integrated evidence supporting recommendations from scientific bodies addressing obesity in adults, including: the National Heart, Lung, and Blood Institute, the World Health Organization, the Canadian Task Force on Preventive Health Care, and the US Preventive Task Force. In addition, pertinent studies were identified from MEDLINE, Database of Abstracts of Reviews of Effectiveness, and the Cochrane Database.
Results: (1) manage obesity as a chronic relapsing disease; (2) use BMI as a vital sign to screen for overweight/obese patients and to decide treatment (positive predictive value of 97%); (3) modest weight loss (10%) positively affects prevention/treatment of hypertension (NNT = 3), diabetes (NNT = 9), and hyperlipidemia; (4) effective treatments exist for overweight/obese patients and a combination of diet and exercise provides the best results (NNT = 7); (5) counsel patients to achieve a goal of 10% reduction in weight (500 to 800 kcal/day decrease to affect 1- to 2-pound loss/week); (6) counsel patients to exercise to achieve a goal of any increased energy expenditure.
Conclusions: Weight loss has an impact on important disease states and risk factors. Effective strategies exist for the management of obesity when viewed as a chronic relapsing disease.
Introduction
Obesity is epidemic worldwide, and the United States is no exception. Initial results from the 1999 National Health and Nutrition Survey (NHANES) estimate that 61% of US adults are either overweight or obese; adult obesity nearly doubled, increasing from 15% to 27%, during the 14-year reporting period of NHANES III.[5] Strong evidence links obesity to increased morbidity and mortality.[1,6] Psychosocial consequences are substantial as well,[7-10] including a limitation of capacity for physical activity.[11] Moreover, in the United States, the economic costs of obesity have been assessed at 6.8% of total health costs.[12] Although prospective studies of weight loss by obese persons have not demonstrated improvements in long-term morbidity and mortality, reductions have been shown in risk factors for several cardiovascular, pulmonary, and cancer conditions.[1,6,13-15]
Primary care physicians are in a special position to treat obesity. It is estimated that primary care doctors see 11.3% of the US population every month[16] and that overweight patients are over-represented in this patient population.[17] A number of scientific bodies have published treatment recommendations based on systematic reviews of the literature[6,15,18-21] that could be used by primary care physicians. Although there are some differences of opinion, there is consensus on the treatment of obese patients with comorbid conditions (diabetes, hypertension, and hyperlipidemia) and partial agreement on treatment of all overweight and obese[16,17] patients. However, these disparate treatment recommendations currently are not framed in such a way that they can be integrated easily into the other competing demands of primary care practice. Perhaps because of this, only 27% to 42% of obese patients seeking medical help are advised by their health professionals to lose weight.[22,23]
This applied evidence-based review provides a rationale for the diagnosis and treatment of obesity in adults by providing test characteristics for the body mass index (BMI) and number needed to treat (NNT) for relevant treatments, thereby synthesizing the evidence and recommendations in a way that we feel will be useful to practicing clinicians. We believe that obesity should be approached as a chronic disease with genetic, environmental, and behavioral components.[24,25] We acknowledge the public health aspect of obesity,[1] an epidemic requiring measures aimed at its social determinants,[1,26,27] that are beyond the direct scope of the primary care encounter. Furthermore, we recognize that because of variation in physician style and patient characteristics, a "one size fits all" cookbook approach to the treatment of obesity will not be helpful. The purpose of this review is to provide a resource for primary care physicians that can be adapted for use in the way most appropriate for any individual practice.
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52. Finer N, Bloom SR, Frost GS, Banks LM, Griffiths J. Sibutramine is effective for weight loss and diabetic control in obesity with type 2 diabetes: a randomised, double-blind, placebo-controlled study. Diabetes Obes Metab 2000;2:105-12.
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57. Segal KR, Dunaif A, Gutin B, Albu J, Nyman A, Pi-Sunyer FX. Body composition, not body weight, is related to cardiovascular disease risk factors and sex hormone levels in men. J Clin Invest 1987;80: 1050-5.
58. Curtin F, Morabia A, Pichard C, Slosman DO. Body mass index compared to dual-energy x-ray absorptiometry: evidence for a spectrum bias. J Clin Epidemiol 1997;50:837-43.
59. Smalley KJ, Knerr AN, Kendrick ZV, Colliver JA, Owen OE. Reassessment of body mass indices. Am J Clin Nutr 1990;52:405-8.
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-Does birth weight predict childhood obesity?
Robert K Persons, DOTristan L. Sevdy, MD, FAAFP
Eglin Family Medicine Residency, Eglin Air Force Base, Fla
William Nichols, MLS
Eglin Air Force Base, Fla
Evidence-based answer
Yes. A birth weight greater than 4,000 g is associated with an increased risk of obesity in both childhood and adolescence (strength of recommendation [SOR]: B, systematic review and multiple cohort studies).
Clinical commentary
Lifestyle matters, too
David Krulak, MD, MPH
Camp Lejeune, NC
Few people have more questions than brand-new parents. Physicians often answer these inquiries from their pool of clinical experience or pearls handed down by mentors. It’s refreshing to be able to address a parental query on the basis of good evidence rather than empiricism.
The data compel us to inform parents that a new baby who weighs more than 4 kg is at increased risk of childhood obesity. However, all parents should be counseled that the lifestyle choices they make for their child are far more likely than birth weight to influence future obesity. Education about appropriate diet and physical activity is the bedrock from which to attack the childhood obesity epidemic.
Evidence summary
The number of children 2 years and older who are overweight has tripled in the past 2 decades; the current prevalence of over-weight children and adolescents in the US is 15%.1 By contrast with adults—in whom overweight and obesity are defined separately as a body mass index (BMI) above 25 kg/m2 and 30 kg/m2, respectively—overweight and obesity are synonymous in children and are defined as a BMI above the 95th percentile for age and sex.2 Children and adolescents with a BMI between the 85th and 95th percentiles are considered at risk for overweight.2
Overweight children are vulnerable to adverse health outcomes, including insulin resistance, hyperlipidemia, hypertension, depression, sleep apnea, asthma, steatohepatitis, genu varum, and slipped capital femoral epiphysis.2 The many variables that have been suggested to influence childhood obesity include birth weight, gestational age, parental obesity, socioeconomic status, single parent household, and birth order.3-5
Birth weight and later BMI: Consistently linked
A systematic review of 19 longitudinal, observational studies comparing birth weight with later BMI indicates that the association between the 2 is positive and consistent in multiple cohorts.3 Eleven studies focused on outcomes in childhood; another 8 measured outcomes into adulthood.
Fifteen of the 19 studies (79%), ranging in size from 1028 to 92,940 subjects, found a positive association between birth weight and later BMI. However, the data were too heterogeneous to combine into a single summary measure. One representative study quantified the relative risk (RR) for severe obesity (>95th percentile BMI) at 5 years of age as 1.7 (95% confidence interval [CI], 1.2-2.9) for birth weights between the 85th and 94th percentiles and 1.8 (95% CI, 1.1-2.9) for birth weights greater than the 95th percentile.3 Studies that didn’t find such an association had smaller sample sizes (137 to 432 subjects) and, therefore, may have lacked the power to detect an association.
Gestational diabetes. A subsequent retrospective cohort survey of 14,881 children born to mothers with gestational diabetes—and controlled for age, sex, and Tanner stage—found that the odds ratio (OR) for adolescent overweight was 1.4 (95% CI, 1.2-1.6) for each 1-kg increment in birth weight.4 The correlation persisted (OR=1.3; 95% CI, 1.1-1.5) when other covariates were controlled (television viewing, physical activity, energy intake, breastfeeding duration, birth order, household income, mother’s smoking, dietary restraint, and mother’s current BMI).
Large for gestational age. A US national cohort study of 3192 children adjusted for gestational age, found that large-for-gestational-age (LGA) infants with birth weights above the 90th percentile remained longer and heavier through 83 months of life.5 The triceps and subscapular skinfold measurements at 3 years of age for children born LGA were virtually identical to those of children born appropriate for gestational age, but by 6 years of age, skinfold measurements had diverged considerably, to more than 0.60 standard deviations. The researchers concluded that intrauterine growth is associated with obesity in early childhood.
Finally, a large Chinese population-based, case-control study (N=1322), found birth weight above 4.0 kg to be a risk factor for obesity in preschool-age children (OR=3.77; 95% CI, 2.06-6.29).6 The absolute rate of overweight increased from 8% to 26% among LGA infants.
In adolescence, parental weight may be a factor
A prospective cohort study of 1993 white LGA infants found a greater propensity to become obese in adolescence, but only if their mothers or fathers were also obese (RR=5.7).7 Children with lean parents did not have an increased risk of being over-weight in adolescence.
Recommendations
Although major organizations don’t focus on infant birth weight as a predictor of overweight, they do address childhood obesity. The American Academy of Pediatrics states that genetic, environmental, or combinations of risk factors predisposing children to obesity can and should be identified.2 The US Preventive Services Task Force concludes that the evidence is insufficient to recommend for or against routine screening for overweight in children and adolescents as a means of preventing adverse health outcomes (Grade I recommendation).1
• ACKNOWLEDGEMENTS •
The opinions and assertions contained herein are the private view of the author and not to be construed as official or as reflecting the view of the US Air Force Medical Service or the US Air Force at large.
REFERENCES
1. US Preventive Services Task Force Screening and interventions for childhood obesity. Guide to Clinical Preventive Services. Rockville, MD: Agency for Healthcare Research and Quality; 2005.
2. Krebs NF, Jacobson MS. and the American Academy of Pediatrics Committee on Nutrition. Prevention of pediatric overweight and obesity. Pediatrics. 2003;112:424–430.
3. Parsons TJ, Power C, Logan S, et al. Childhood predictors of adult obesity: a systematic review. Int J Obes Relat Metab Disord. 1999;23(suppl 8):S1–S107.
4. Gillman MW, Rifas-Shiman S, Berkey CS, et al. Maternal gestational diabetes, birth weight, and adolescent obesity. Pediatrics. 2003;111(3):e221–226.
5. Hediger ML, Overpeck MD, McGlynn A, et al. Growth and fatness at three to six years of age of children born small- or large-for-gestational age. Pediatrics. 1999;104:e33.
6. He Q, Ding ZY, Fong DY, et al. Risk factors of obesity in preschool children in China: a population-based case-control study. Int J Obes Relat Metab Disord. 2000;24:1528–1536.
7. Frisancho AR. Prenatal compared with parental origins of adolescent fatness. Am J Clin Nutr. 2000;72:1186–1190.
Is The Obesity Epidemic Exaggerated?
ScienceDaily (Feb. 5, 2008) — Last week, the UK health secretary declared that we are in a grip of an obesity epidemic, but does the evidence stack up? Researchers debate the issue in the British Medical Journal.
Claims about an obesity epidemic often exceed the scientific evidence and mistakenly suggest an unjustified degree of certainty, argue Patrick Basham and John Luik.
For example, the average population weight gain in the United States in the past 42 years is 10.9kg or 0.26kg a year. Yet, between 1999-2000 and 2001-2002, there were no significant changes in the prevalence of overweight or obesity among US adults or in the prevalence of overweight among children.
Furthermore, they say, the categories of normal, overweight, and obese is entirely arbitrary and at odds with the underlying evidence about the association between body mass index and mortality.
For example, the study on which the bands for overweight and obesity in the US are based found that the death risks for men with a body mass index of 19-21 were the same as those for men who were overweight and obese (29-31). Other studies have shown negligible differences between body mass index and death rates.
The association of overweight and obesity with higher risks of disease is equally unclear, they write. And, despite supposedly abnormal levels of overweight and obesity, life expectancy continues to increase.
They suggest that some public health professionals may have deliberately exaggerated the risks of overweight and obesity, and our capacity to prevent or treat them on a population wide basis, in the interests of health. They warn that this has unwelcome implications for science policy and for evidence based medicine.
But Robert Jeffery and Nancy Sherwood argue that a large body of scientific evidence shows that obesity is a major global health problem.
In the US, the prevalence of obesity in 1976-80 was 6.5% among 6-11 year olds and 5% among 12-17 year olds. In 2003-4 it was 19% and 17% respectively. Europe can also expect to see the numbers of overweight and obese children rising by around 1.3 million a year by 2010.
The risks of obesity on many serious health conditions including high blood pressure, diabetes, heart disease and some forms of cancer, are also serious and well established, they write.
Most health economists and epidemiologists agree that the contribution of obesity to current healthcare costs is high and that it is likely to get much higher. Some have argued that we may even see real falls in life expectancy within a few decades, they add.
In summary, a large body of evidence documents that over-nutrition and obesity are a major global health problem, say the authors. With the continuing rise in obesity and limited treatment efficacy, options for averting a poor public health outcome seem to rest either on the hope that scientists are wrong in their projections or speedy investment in the development of more effective public health measures to deal with it. They think the second option a more prudent scientific and policy choice.
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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by BMJ-British Medical Journal, via EurekAlert!, a service of AAAS.