Table 1. Main limitations identified in existing systematic reviews that served as constraints to interpretation of the evidence and what we did to address them in our review.

What answering the research question requires	Why was it identified as a limitation in existing reviews?	What we did to address identified limitations in our review
Explicit definition of treatment and control diets with complete macronutrient profile	If unclear, any effects seen on weight loss and CVD risk factors cannot be attributed to a well-defined intervention diet compared to a well-defined control diet	Used explicit cut-off ranges for macronutrients for treatment and control diets; the complete macronutrient profile of intervention diets had to be available (proportions of total energy intake)
Recommended energy intake in treatment and control groups needs to be similar	If different, any effects seen on weight loss and CVD risk factors would be confounded by total energy intake	Only included isoenergetic diet comparisons
Co-interventions, such as drugs given as part of the intervention, or recommendations for exercise, need to be similar in the comparison groups	If different, any effects on CVD risk factors could be confounded by co-interventions	Only included interventions with a diet component alone, or combined interventions that were similar to prevent confounding by co-interventions
Appropriate study design for the question	Methodological heterogeneity: some reviews included both controlled and uncontrolled trials	Only included randomised controlled trials
Meaningful and comparable follow-up in trials needs to be considered	Outcomes of trials with different follow-ups were pooled; generalised conclusions about weight loss may be skewed by early changes; or follow-up may be insufficient to detect CVD risk factor changes	Only included studies with 12 weeks or more follow-up; and outcomes were grouped by defined lengths of follow-up

CVD: cardiovascular disease.

Note: see Supporting Information S1 for the critical summary of existing systematic reviews.