|Weight loss interventions in young people (18 to 25 year olds): a systematic review
|Poobalan AS, Aucott LS, Precious E, Crombie IK, Smith WC
The review concluded that weight loss interventions showed some effects in people aged 18 to 25 years. The authors' conclusions reflect the evidence presented, but differences between the studies, small sample sizes and limitations of the analysis make the reliability of the conclusions uncertain.
To evaluate the effectiveness of weight loss interventions in young adults (18 to 25 years old) who are vulnerable to weight gain.
MEDLINE, EMBASE, CINAHL, PsycINFO and The Cochrane Library were searched from 1980 to March 2008 with no language restrictions. Search terms were reported. Reference lists of retrieved studies and review articles were scanned for additional studies.
Randomised controlled trials (RCTs), controlled clinical trials, non-randomised trials and cohort studies with control groups that assessed lifestyle weight loss interventions aimed at young adults (18 to 25 years) were eligible for inclusion. Studies of drug and surgical interventions and studies in children, adolescents and young people with chronic diseases were excluded. Abstracts and studies that did not specifically report that they included only young adults were excluded. Outcomes of interest were weight loss or change to risk factors (total cholesterol, high-density lipoprotein (HDL) cholesterol, blood glucose, insulin and maximum oxygen uptake).
Interventions in the included studies included diet and exercise, behavioural and motivational programmes, combined intervention (diet, physical activity and behavioural skills) and conjugated linolenic acid. More than half of the included studies had female participants only, some had males only and two studies had both. Duration of interventions ranged from two to 56 weeks; 12 weeks was the most common. Most studies assessed outcomes immediately after the intervention.
Two reviewers independently assessed studies for inclusion initially and then by one reviewer.
Assessment of study quality
Validity was assessed using the Jadad scale and criteria adapted from the Cochrane Collaboration. Assessment criteria included random allocation of concealment, comparability of groups at baseline, blinding of healthcare providers and outcomes assessors, follow-up time, percentage of follow-up, drop-out details, use of validated outcome measures, quality of reporting of outcomes and intention-to-treat (ITT) analysis (maximum score 20). Study quality was categorised as strong (more than 15 points), moderate (between 10 and 15 points) and weak (less than 10 points).
The authors did not state how many reviewers assessed validity.
Data for relevant outcomes were extracted and used to calculate mean differences and standard deviations.
Two reviewers independently extracted data. Disagreements were resolved through discussion.
Methods of synthesis
Any study groups that received an intervention (including groups defined as control groups by primary study authors) were analysed longitudinally before and after the intervention. Interventions were grouped by category. Pooled weighted mean differences (WMD) and corresponding 95% confidence intervals (CIs) were calculated using a fixed-effect model (statistical heterogeneity absent) or a random-effects model (significant statistical heterogeneity). A meta-linear regression model was used to assess the association of risk factors with weight status.
Results of the review
Fourteen studies (499 participants, range 16 to 67) were included in the review: nine randomised controlled trials (RCTs), one controlled clinical trial, three non-RCTs and one retrospective controlled cohort study. Only two studies were considered to be of strong methodological quality, 10 were considered to be moderate and two were considered to be weak. Twenty study groups were included in the analysis.
Overall there were a non-statistically significant reduction in weight loss after the intervention irrespective of intervention type (WMD -3.01 kg, 95% CI -8.5 to 2.5; 20 groups). There were non-statistically significant reductions in weight post-intervention for behavioural or motivational interventions (WMD -2.40kg, 95% CI -5.4 to 0.6 kg; four groups). There were significant reductions for interventions that combined diet, exercise and motivational skills (WMD -2.96kg, 95% CI -4.4 to -1.5; three groups). Weight loss reductions for aerobic exercise interventions post-intervention were not statistically significant (WMD -3.37kg, 95% CI -10.75 to 3.99; 10 groups).
Regardless of intervention, there were significant improvements post-intervention in HDL cholesterol (WMD 0.06mmolL-1, 95% CI 0.03 to 0.19), insulin levels (WMD -9.65pmolL-1, 95% CI -15.35 to -3.96) and glucose levels (WMD -0.26mmolL-1, 95% CI -0.41 to -0.11). There were also improvements post intervention in total cholesterol level and maximum oxygen uptake, but these differences were not significant.
Weight loss interventions showed some effects in young people (aged 18 to 25 years). The varied components and duration of interventions made it difficult to identify the most effective intervention for weight loss in this age group.
The review question was clearly stated. Inclusion and exclusion criteria were clearly defined. Some relevant sources were searched. A lack of language restrictions reduced the risk of language bias. No attempts were made to locate unpublished studies and this introduced potential for publication bias. The authors' original intention was to evaluate controlled studies only, but most of the included studies only conducted a longitudinal before-and-after analysis. Validity was assessed using appropriate criteria, but few details were reported. Appropriate methods to reduce reviewer error and bias were used for study selection and data extraction; it was unclear whether similar methods were used for the validity assessment.
Studies were combined in a within-group analysis on pre-post intervention data using either a random effect or fixed effect model depending on heterogeneity. The authors did not report what statistical tests were used to assess heterogeneity. Analysis of uncontrolled data was subject to potential biases and confounding factors. Differences in the included studies in terms of study designs, participants, settings and aims may have limited the generalisability of the results and it may not have been appropriate to combine such heterogeneous studies in a meta-analysis. As the authors noted, most of the included studies had small sample sizes, short-term interventions and no follow-up after completion of the intervention.
The authors' conclusions reflect the evidence presented, but differences between the studies, small sample sizes and limitations of the analysis make the reliability of the conclusions uncertain.
Implications of the review for practice and research
Practice: The authors did not state any implications for practice.
Research: The authors stated that long-term cohort studies with larger samples may be useful to assess health benefits associated with weight loss/maintenance programmes. Further research was needed to explore young people's reasons for participation and their choice of intervention in obesity prevention and treatment programmes.
Poobalan AS, Aucott LS, Precious E, Crombie IK, Smith WC. Weight loss interventions in young people (18 to 25 year olds): a systematic review Obesity Reviews 2010; 11(8): 580-592
Subject indexing assigned by NLM
Adolescent; Adult; Behavior Therapy; Clinical Trials as Topic; Cognitive Therapy; Cohort Studies; Diet, Reducing; Female; Humans; Male; Obesity /epidemiology /prevention & control /therapy; Treatment Outcome; Weight Loss; Young Adult
Database entry date
This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.