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Guidelines on Overweight and Obesity: Electronic Textbook
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APPENDIX I.A.1. GUIDELINES DEVELOPMENT METHODOLOGY

The panel has attempted to provide primary care practitioners with recommendations regarding effective strategies to evaluate and treat overweight and obesity in adults. The panel anticipates that the recommendations also will be followed by the large proprietary weight loss industry in the United States. The guideline is based on a systematic review of the scientific literature published in MEDLINE from January 1980 through September 1997. This was done in the interest of time and economy. This information was supplemented by material provided by the panel and a search of appropriate references in eligible articles. The panel identified randomized controlled trials as the strongest level of evidence for the evaluation of treatment efficacy. Thus, evidence from randomized controlled trials (RCTs) serves as the basis for many of the recommendations contained in this guideline.

However, in some instances, the panel had to make recommendations in the absence of RCTs.  Each evidence statement (other than those with no available evidence) and each recommendation is categorized by level of evidence (A through D) as described in Table A-1.

Table A-1: Evidence Categories

Evidence Category Sources of Evidence Definition
A
Randomized controlled trials (rich body of data) Evidence is from endpoints of well-designed RCTs (or trials that depart only minimally from randomization) that provide a consistent pattern of findings in the population for which the recommendation is made. Category A therefore requires substantial numbers of studies involving substantial numbers of participants.
B
Randomized controlled trials (limited body of data) Evidence is from endpoints of intervention studies that include only a limited number of RCTs, post hoc or subgroup analysis of RCTs, or meta-analysis of RCTs. In general, Category B pertains when few randomized trials exist, they are small in size, and the trial results are somewhat inconsistent, or the trials were undertaken in a population that differs from the target population of the recommendation.
C
Nonrandomized trials  Observational studies Evidence is from outcomes of uncontrolled or nonrandomized trials or from observational studies.
D
Panel Consensus Judgment Expert judgment is based on the panel's synthesis of evidence from experimental research described in the literature and/or derived from the consensus of panel members based on clinical experience or knowledge that does not meet the above-listed criteria. This category is used only in cases where the provision of some guidance was deemed valuable but an adequately compelling clinical literature addressing the subject of the recommendation was deemed insufficient to justify placement in one of the other categories (A through C).

Statements for which there is no available evidence are so indicated.

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