Effects of weight loss interventions for adults who are obese on mortality, cardiovascular disease and cancer: a systematic review and meta-analysis

Chenhan Ma, Alison Avenell, Mark Bolland, Jemma Hudson, Fiona Stewart, Clare Robertson, Pawana Sharma, Cynthia Fraser, Graeme MacLennan

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Abstract

Objective
To assess if weight loss interventions for adults with obesity affect all-cause, cardiovascular and cancer mortality, cardiovascular disease, cancer, and body weight.

Design
Systematic review and meta-analysis of randomised controlled trials (RCTs) using random effects, estimating risk ratios (RRs) and mean differences (MDs). Heterogeneity investigated using Cochran’s Q and I2 statistics. Quality of evidence assessed by GRADE criteria.

Data sources
We searched Medline, Embase, the Cochrane Central Register of Controlled Trials, and full texts in our trials’ registry for data not evident in databases. We contacted authors for unpublished data.

Eligibility criteria for selecting studies
RCTs of dietary interventions targeting weight loss, with or without exercise advice or programmes, for adults with obesity and follow-up ≥ 1 year.

Results
We included 54 RCTs with 30,206 participants. All but one trial evaluated low-fat reducing diets. For the primary outcome, there was high quality evidence that weight loss interventions decrease all-cause mortality (34 trials, 685 events; RR 0.82, 95% CI (Confidence Interval): 0.71 to 0.95), 6 fewer deaths per 1000 participants (95% CI 2 fewer to 10 fewer). For other primary outcomes there was moderate quality evidence for an effect on cardiovascular mortality (8 trials, 134 events; RR 0.93, 95% CI: 0.67 to 1.31) and very low quality evidence for an effect on cancer mortality (8 trials, 34 events; RR 0.58, 95% CI 0.30 to 1.11).

Twenty four trials (15,176 participants) reported high quality evidence on participants developing new cardiovascular events (1043 events; RR 0.93, 95% CI 0.83 to 1.04).

Nineteen trials (6330 participants) provided very low quality evidence on participants developing new cancers (103 events; RR 0.92, 95% CI 0.63 to 1.36).

Conclusions
Weight reducing diets, usually low in fat and saturated fat, with or without exercise advice or programmes, may reduce premature all-cause mortality in adults with obesity.
Original languageEnglish
Article numberj4849
JournalBMJ
Volume359
DOIs
Publication statusPublished - 14 Nov 2017

Keywords

  • obesity
  • weight reduction
  • reducing diet
  • mortality
  • cardiovascular disease
  • cancer
  • systematic review
  • randomised controlled trials

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