Therapeutic Potential of Astaxanthin for Body Weight Regulation: A Systematic Review and Meta-Analysis with Dose–Response Assessment

Background/Objectives: Astaxanthin, a naturally occurring carotenoid renowned for its potent antioxidant properties, has been proposed as a dietary supplement for weight management due to its potential effects on adipose tissue and skeletal muscle metabolism, as well as its anti-inflammatory properties. This meta-analysis systematically evaluated the impact of astaxanthin supplementation on body mass index (BMI) and body weight in adult populations. Methods: Comprehensive searches of reputable databases were conducted, adhering to the PRISMA guidelines, with statistical analyses performed using Jamovi. Results: The study incorporated data from nine clinical trials. Pooled results indicated no significant reduction in the context of BMI (−0.2162; 95% CI: −0.4697 to 0.0374) and a non-significant decrease in body weight (0.0230; 95% CI: −0.4534 to 0.4994) relative to control groups. The heterogeneity observed across studies was 30.1251% (p = 0.1593) for BMI and 73.3885% (p = 0.0002) for body weight management. The dose–response analysis showed no statistically significant association between astaxanthin dosage and outcomes related to BMI and body weight management. Additionally, statistical assessment of funnel plot asymmetry indicated no evidence of publication bias. Conclusions: The findings indicate that astaxanthin does not provide benefits in BMI regulation nor in weight control management, highlighting the need for additional large-scale and long-term clinical trials. This study contributes to the growing body of evidence on the role of nutraceuticals in metabolic health, providing a foundation for future clinical recommendations.