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Review
. 2014 Jul 9;9(7):e100652.
doi: 10.1371/journal.pone.0100652. eCollection 2014.

Low carbohydrate versus isoenergetic balanced diets for reducing weight and cardiovascular risk: a systematic review and meta-analysis

Celeste E Naude  1 , Anel Schoonees  1 , Marjanne Senekal  2 , Taryn Young  3 , Paul Garner  4 , Jimmy Volmink  3
Affiliations
Review

Low carbohydrate versus isoenergetic balanced diets for reducing weight and cardiovascular risk: a systematic review and meta-analysis

Celeste E Naude et al. PLoS One. .

Erratum in

Abstract

Background: Some popular weight loss diets restricting carbohydrates (CHO) claim to be more effective, and have additional health benefits in preventing cardiovascular disease compared to balanced weight loss diets.

Methods and findings: We compared the effects of low CHO and isoenergetic balanced weight loss diets in overweight and obese adults assessed in randomised controlled trials (minimum follow-up of 12 weeks), and summarised the effects on weight, as well as cardiovascular and diabetes risk. Dietary criteria were derived from existing macronutrient recommendations. We searched Medline, EMBASE and CENTRAL (19 March 2014). Analysis was stratified by outcomes at 3-6 months and 1-2 years, and participants with diabetes were analysed separately. We evaluated dietary adherence and used GRADE to assess the quality of evidence. We calculated mean differences (MD) and performed random-effects meta-analysis. Nineteen trials were included (n = 3209); 3 had adequate allocation concealment. In non-diabetic participants, our analysis showed little or no difference in mean weight loss in the two groups at 3-6 months (MD 0.74 kg, 95%CI -1.49 to 0.01 kg; I2 = 53%; n = 1745, 14 trials; moderate quality evidence) and 1-2 years (MD 0.48 kg, 95%CI -1.44 kg to 0.49 kg; I2 = 12%; n = 1025; 7 trials, moderate quality evidence). Furthermore, little or no difference was detected at 3-6 months and 1-2 years for blood pressure, LDL, HDL and total cholesterol, triglycerides and fasting blood glucose (>914 participants). In diabetic participants, findings showed a similar pattern.

Conclusions: Trials show weight loss in the short-term irrespective of whether the diet is low CHO or balanced. There is probably little or no difference in weight loss and changes in cardiovascular risk factors up to two years of follow-up when overweight and obese adults, with or without type 2 diabetes, are randomised to low CHO diets and isoenergetic balanced weight loss diets.

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Conflict of interest statement

Competing Interests: No authors currently receive or have received funds from commercial organizations that could directly or indirectly benefit from the question addressed by this research or its findings. PG is Director of Evidence Building and Synthesis Research Consortium that receives money to increase the number of evidence-informed decisions by intermediary organizations, including WHO and national decision makers that benefit the poor in middle and low income countries. The Centre for Evidence-based Health Care at Stellenbosch University receives a grant from the Consortium for influencing evidence-informed decisions in the sub-Saharan region, and to develop capacity of researchers to respond to requests for timely, informed systematic reviews to inform national policies. The Heart and Stroke Foundation South Africa requested this review but did not contribute in any way financially or other, to its implementation. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials.

Figures

Figure 1
Figure 1. Flow diagram illustrating the search results and selection process, as well as the variants of the low carbohydrate diets used as treatments in the included trials.
The high fat variant of low carbohydrate diets is low in carbohydrates (<45% of total energy), high in fat (>35% of total energy) and high in protein (>20% of total energy). The high protein variant of low carbohydrate diets is low in carbohydrates (<45% of total energy), has a recommended proportion of fat (20 to 35% of total energy) and is high in protein (>20% of total energy).
Figure 2
Figure 2. Risk of bias: systematic review authors' judgements about each risk of bias item presented as percentages across all included trials using the Cochrane risk of bias tool (n = 19).
Figure 3
Figure 3. Forest plot of low carbohydrate versus balanced diets in overweight and obese adults for weight loss (kg) at 3–6 months.
Figure 4
Figure 4. Forest plot of low carbohydrate versus balanced diets in overweight and obese adults for weight loss (kg) at 1–2 years.
Figure 5
Figure 5. Forest plot of low carbohydrate versus balanced diets in overweight and obese adults with type 2 diabetes for weight loss (kg) at 3–6 months.
Figure 6
Figure 6. Forest plot of low carbohydrate versus balanced diets in overweight and obese adults with type 2 diabetes for weight loss (kg) at 1–2 years.
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Grants and funding

This review was funded by the Effective Health Care Research Consortium and the South African Medical Research Council. CN is funded by the Centre for Evidence-based Health Care (CEBHC) and the South African Medical Research Council. AS and TY are funded by CEBHC. MS is funded by University of Cape Town. JV is funded by Stellenbosch University and the South African Cochrane Centre. PG is funded by the University of Liverpool and the Evidence Building and Synthesis Research Consortium. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.