More than one-third of individuals are overweight and obese in the world. Their risks of chronic health conditions are increased, which places additional burden on their family, caregivers, and healthcare system. Dietary modification is widely used for overweight and obese individuals. We investigated the effects of ketogenic diet (KD) and low-carbohydrate diet (LCD) in improving body weight (BW), body mass index (BMI), fat mass (FM), and body fat percentage (BFP) in overweight or obese individuals. A three-step approach was adopted for searching relevant randomised controlled trials (RCTs) across five electronic databases. Two reviewers conducted the screening, review, and quality appraisal independently. A random-effects model was used because of variations in intervention and participant characteristics. Sensitivity and subgroup analyses were conducted to assess heterogeneity and variations in the results, respectively. Thirty-three RCTs involving 2821 individuals were included. Overall meta-analysis results indicated that KD/LCD significantly reduced BW, BMI, and BFP, but not FM, in individuals with a carbohydrate intake of ≤100 g/d. Subgroup analyses revealed significant improvements in BW, BMI, and FM in individuals on KD/LCD for ≥1 month and in all parameters for those with a carbohydrate intake of ≤50 g/d. High statistical heterogeneity was noted because of variations in interventions and participant characteristics. Adults with overweight or obesity should consume KD/LCD for ≥1 month and limit carbohydrate intake to ≤50 g/d. Further multicentre or multicountry RCTs are needed to improve the generalisability of our findings. We recommend integrating text messaging and evidence-based information to support interventions and ensuring stringent medical supervision throughout the intervention. CRD42022353074.

The use of medication is effective in managing metabolic syndrome (MetS), but side effects have led to increased attention on using nutraceuticals and supplements. Astaxanthin shows positive effects in reducing the risk of MetS, but results from individual studies are inconclusive. This systematic review summarizes the latest evidence of astaxanthin in adults with risk factors of MetS. A systematic search of English and Chinese randomized controlled trials in 14 electronic databases from inception to 30 June 2021 was performed. Two reviewers independently screened the titles and abstracts, and conducted full-text review, quality appraisal, and extraction of data. Risk of bias was assessed by PEDro. A total of 7 studies met the inclusion criteria with 321 participants. Six studies were rated to have excellent methodological quality, while the remaining one was rated at good. Results show marginal effects of astaxanthin on reduction in total cholesterol and systolic blood pressure, and a significant attenuating effect on low-density lipoprotein cholesterol. Further robust evidence is needed to examine the effects of astaxanthin in adults at risk of MetS.