Study designs of evaluations included in the review
Inclusion criteria relating to the study design were not specific. Studies that did not state the duration of treatment, or if the duration was less than 12 weeks, were excluded. Case series had to have a follow-up period of at least 12 months to be included. Retrospective case series, and case series that did not report the number of participants initially included in the study, were excluded.
Specific interventions included in the review
Studies of commercial weight loss programmes that were assessed under the same conditions as would be expected in practice were eligible for inclusion. The programmes varied in terms of staff qualifications, diet, physical activity, behaviour modification and support.
Participants included in the review
Studies conducted in the USA on an adult population of at least 10 participants were eligible for inclusion. The number of participants in the included studies ranged from 40 to 517, with the majority of the participants being women (from 48 to 100%; 3 trials were comprised exclusively of women).
Outcomes assessed in the review
Inclusion criteria relating to the outcomes were not specified. The outcomes reported were maximum and long-term weight change.
How were decisions on the relevance of primary studies made?
Two reviewers independently selected studies for the review.