Low Carbohydrate versus Isoenergetic Balanced Diets for Reducing Weight and Cardiovascular Risk: A Systematic Review and Meta-Analysis

Abstract

BackgroundSome 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 FindingsWe 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.ConclusionsTrials 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.

In the footsteps of Einstein, Sagan and Barnard: Identifying South Africa’s most visible scientists

“…Fellow scientists have challenged the scientific basis of the low-carbohydrate-high-fat diet 60 , while colleagues at the University of Cape Town have accused him of making outrageous and unproven claims and have distanced themselves from his dietary recommendations 61 .…”

Naude et al. avoid answering the essential question: Mistake or mischief?

“…To the Editor: It is common cause that the Naude/Stellenbosch University/University of Cape Town meta-analysis [1] played a decisive role in the multimillion rand prosecution of Prof. T Noakes by the Health Professions Council of South Africa (HPCSA), which has now been ongoing for more than 3 years. The complainant, Claire JulsingStrydom, referred to the importance of a meta-analysis generally and/or the Naude et al [1] meta-analysis specifically on 12 separate occasions during her testimony.…”

“…The complainant, Claire JulsingStrydom, referred to the importance of a meta-analysis generally and/or the Naude et al [1] meta-analysis specifically on 12 separate occasions during her testimony. On 24 November 2015, under oath, she said of the Naude et al [1] publication: 'So before any media statements could be made we had to get that information and all these associations were waiting on that. It is not like the way you are saying it, it is not like everybody joined together to now make a statement against Prof. Noakes.…”

“…We were all waiting for the evidence to be published. ' Another prosecution witness, Prof. H Vorster, referred to the Naude et al [1] meta-analysis five times and quoted from it verbatim once. A third prosecution witness, Prof. A Dhansay, referenced the meta-analysis twice, using the term 'Cochrane' to ensure that it was afforded the appropriate esteem.…”

“…Without the 'correct conclusion' from this meta-analysis, it is possible that the HPCSA trial against Noakes might never have happened. Therefore, the importance of the Naude et al [1] meta-analysis extends far beyond any role purely as a neutral scientific publication.…”