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Meta-Analysis
. 2020 Apr 1;369:m696.
doi: 10.1136/bmj.m696.

Comparison of Dietary Macronutrient Patterns of 14 Popular Named Dietary Programmes for Weight and Cardiovascular Risk Factor Reduction in Adults: Systematic Review and Network Meta-Analysis of Randomised Trials

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Meta-Analysis

Comparison of Dietary Macronutrient Patterns of 14 Popular Named Dietary Programmes for Weight and Cardiovascular Risk Factor Reduction in Adults: Systematic Review and Network Meta-Analysis of Randomised Trials

Long Ge et al. BMJ. .
Free PMC article

Abstract

Objective: To determine the relative effectiveness of dietary macronutrient patterns and popular named diet programmes for weight loss and cardiovascular risk factor improvement among adults who are overweight or obese.

Design: Systematic review and network meta-analysis of randomised trials.

Data sources: Medline, Embase, CINAHL, AMED, and CENTRAL from database inception until September 2018, reference lists of eligible trials, and related reviews.

Study selection: Randomised trials that enrolled adults (≥18 years) who were overweight (body mass index 25-29) or obese (≥30) to a popular named diet or an alternative diet.

Outcomes and measures: Change in body weight, low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol, systolic blood pressure, diastolic blood pressure, and C reactive protein at the six and 12 month follow-up.

Review methods: Two reviewers independently extracted data on study participants, interventions, and outcomes and assessed risk of bias, and the certainty of evidence using the GRADE (grading of recommendations, assessment, development, and evaluation) approach. A bayesian framework informed a series of random effects network meta-analyses to estimate the relative effectiveness of the diets.

Results: 121 eligible trials with 21 942 patients were included and reported on 14 named diets and three control diets. Compared with usual diet, low carbohydrate and low fat diets had a similar effect at six months on weight loss (4.63 v 4.37 kg, both moderate certainty) and reduction in systolic blood pressure (5.14 mm Hg, moderate certainty v 5.05 mm Hg, low certainty) and diastolic blood pressure (3.21 v 2.85 mm Hg, both low certainty). Moderate macronutrient diets resulted in slightly less weight loss and blood pressure reductions. Low carbohydrate diets had less effect than low fat diets and moderate macronutrient diets on reduction in LDL cholesterol (1.01 mg/dL, low certainty v 7.08 mg/dL, moderate certainty v 5.22 mg/dL, moderate certainty, respectively) but an increase in HDL cholesterol (2.31 mg/dL, low certainty), whereas low fat (-1.88 mg/dL, moderate certainty) and moderate macronutrient (-0.89 mg/dL, moderate certainty) did not. Among popular named diets, those with the largest effect on weight reduction and blood pressure in comparison with usual diet were Atkins (weight 5.5 kg, systolic blood pressure 5.1 mm Hg, diastolic blood pressure 3.3 mm Hg), DASH (3.6 kg, 4.7 mm Hg, 2.9 mm Hg, respectively), and Zone (4.1 kg, 3.5 mm Hg, 2.3 mm Hg, respectively) at six months (all moderate certainty). No diets significantly improved levels of HDL cholesterol or C reactive protein at six months. Overall, weight loss diminished at 12 months among all macronutrient patterns and popular named diets, while the benefits for cardiovascular risk factors of all interventions, except the Mediterranean diet, essentially disappeared.

Conclusions: Moderate certainty evidence shows that most macronutrient diets, over six months, result in modest weight loss and substantial improvements in cardiovascular risk factors, particularly blood pressure. At 12 months the effects on weight reduction and improvements in cardiovascular risk factors largely disappear.

Systematic review registration: PROSPERO CRD42015027929.

Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the first author) and declare: no support from any organisation for the submitted work. BS reports funding from Mitacs Canada in the past three years, and the International Life Sciences Institute (ILSI), North America to support his graduate work for his 2015 academic year (the ILSI funding is outside the required three year period requested on the ICJME form). In 2016-17, BS worked for the Cornerstone Research Group, a contract research organisation. AS reports personal fees from Dalhousie University. RTT reports grants from Sanofi Canada, outside the submitted work. As part of his recruitment to Texas A&M University, BCJ receives funds from Texas A&M AgriLife Research to support investigator initiated research related to saturated and polyunsaturated fats. Support from Texas A&M AgriLife institutional funds are from interest and investment earnings, not a sponsoring organisation, industry, or company. BCJ also received funding in 2015 from ILSI (outside the required three year period requested on ICJME form) to assess the methodological quality of nutrition guidelines dealing with sugar intake using internationally accepted GRADE (grading of recommendations, assessment, development, and evaluation) and AGREE (appraisal of guidelines for research and evaluation) guideline standards. The authors conducted the review of methodological quality of nutrition guidelines independently without involvement of the funder. No other relationships or activities that could appear to have influenced the submitted work.

Figures

None
Fig 1
Fig 1
Flow diagram of literature selection
Fig 2
Fig 2
Network plots of all included studies for macronutrient patterns and popular named diets
Fig 3
Fig 3
Macronutrient pattern network meta-analysis results with corresponding GRADE (grading of recommendations, assessment, development, and evaluation) certainty of evidence for six month weight loss (kg). Values correspond to difference in median weight loss between column and row at six months, for positive values the diet indicated in the column is favoured (eg, low fat had a median weight loss of 4.37 kg at six months compared with usual diet). Values in bold indicate a statistically significant treatment effect
Fig 4
Fig 4
Macronutrient pattern network meta-analysis results with corresponding GRADE (grading of recommendations, assessment, development, and evaluation) certainty of evidence for six month systolic blood pressure (SBP) and diastolic blood pressure (DBP) reduction (mm Hg). Values correspond to difference in median DBP reduction (above, right of macronutrient patterns) and SBP reduction (below, left of macronutrient patterns)between column and row at six months (eg, low fat had a median DBP reduction of 1.80 and a median SBP reduction of 3.59 compared with dietary advice). Values in bold indicate a statistically significant treatment effect
Fig 5
Fig 5
Macronutrient pattern network meta-analysis results with corresponding GRADE (grading of recommendations, assessment, development, and evaluation) certainty of evidence for reduction in low density lipoprotein (LDL) cholesterol and increase in high density lipoprotein (HDL) cholesterol (mg/dL) at six months. Values correspond to difference in median HDL cholesterol increase (above, right of macronutrient patterns) and LDL cholesterol reduction (below, left of macronutrient patterns) between column and row at six months (eg, low fat had a median HDL cholesterol increase of 0.10 mg/dL and a median LDL cholesterol reduction of 5.47 mg/dL at six months compared with dietary advice). Values in bold indicate a statistically significant treatment effect
Fig 6
Fig 6
Summary of results of popular named diets network meta-analysis for all outcomes at six months. The number is the point estimates of effect in comparison with usual diet

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