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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.
Ge, L, Sadeghirad, B, Ball, GDC, da Costa, BR, Hitchcock, CL, Svendrovski, A, Kiflen, R, Quadri, K, Kwon, HY, Karamouzian, M, et al
BMJ (Clinical research ed.). 2020;369:m696
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Dietary recommendations to combat obesity and its associated risk for heart disease are extensive. Many different diets and patterns of eating are being tried by millions of people, however no systematic review comparing their effectiveness has been performed. This systematic review and meta-analysis aimed to determine the effectiveness of 14 popular diets and diets which restrict certain nutrients on weight loss and heart disease risk. The results identified 121 studies with 21942 patients for inclusion. The Atkins diet, the Zone diet and the Dietary Approaches to Stop Hypertension (DASH) diet were the most effective for weight loss and for reducing blood pressure. Low carbohydrate and low-fat diets achieved similar weight loss when compared to a normal diet. Low carbohydrate diets had less effect on heart disease risk factors than low fat and moderate macronutrient diets. There were no improvements in good cholesterol with any of the diets. Interestingly any benefits on weight loss for any of the diets disappeared after 12 months and this was also observed for heart disease risk, except in those on the Mediterranean diet. It was concluded that most diets show improvements to weight loss and heart disease risk factors over 6 months, however these are largely unsustainable after 12 months. Differences between diets are small and healthcare practitioners could use this study to recommend any number of diets to achieve weight loss and the Mediterranean diet in particular to decrease heart disease risk. However, it is important to understand that this may be a short-term fix and at 12 months patients need to be assessed to ensure that weight loss is sustained.
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.
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Effects of weight loss interventions for adults who are obese on mortality, cardiovascular disease, and cancer: systematic review and meta-analysis.
Ma, C, Avenell, A, Bolland, M, Hudson, J, Stewart, F, Robertson, C, Sharma, P, Fraser, C, MacLennan, G
BMJ (Clinical research ed.). 2017;359:j4849
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Obesity is known to increase the risk of many diseases including cardiovascular disease, various cancers and type 2 diabetes. Interestingly, there is evidence suggesting weight loss in obese adults may be harmful, particularly in older people with cardiovascular disease. The aim of this systematic review was to assess the effect of weight loss interventions for adults with obesity on mortality, cardiovascular disease, cancer and body weight. Based on the 30,000 participants identified, current evidence shows that weight loss interventions significantly decrease all cause mortality. There was also evidence to suggest weight loss is associated with developing new cardiovascular events, though fewer trials reported these outcomes so uncertainty remains around these results. Based on the current literature and this review, the authors conclude weight-reducing diets may reduce all cause mortality in adults with obesity and support public health measures to prevent weight gain and facilitate weight loss.
Abstract
Objective To assess whether 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, and mean differences. Heterogeneity investigated using Cochran's Q and I2 statistics. Quality of evidence assessed by GRADE criteria.Data sources Medline, Embase, the Cochrane Central Register of Controlled Trials, and full texts in our trials' registry for data not evident in databases. Authors were contacted 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 54 RCTs with 30 206 participants were identified. All but one trial evaluated low fat, weight reducing diets. For the primary outcome, high quality evidence showed that weight loss interventions decrease all cause mortality (34 trials, 685 events; risk ratio 0.82, 95% confidence interval 0.71 to 0.95), with six fewer deaths per 1000 participants (95% confidence interval two to 10). For other primary outcomes moderate quality evidence showed an effect on cardiovascular mortality (eight trials, 134 events; risk ratio 0.93, 95% confidence interval 0.67 to 1.31), and very low quality evidence showed an effect on cancer mortality (eight trials, 34 events; risk ratio 0.58, 95% confidence interval 0.30 to 1.11). Twenty four trials (15 176 participants) reported high quality evidence on participants developing new cardiovascular events (1043 events; risk ratio 0.93, 95% confidence interval 0.83 to 1.04). Nineteen trials (6330 participants) provided very low quality evidence on participants developing new cancers (103 events; risk ratio 0.92, 95% confidence interval 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.Systematic review registration PROSPERO CRD42016033217.