Microalgae and Cyanobacteria in the Obesity Evidence Landscape: A PRISMA-ScR Scoping Review with Mechanistic and Safety Mapping

Microalgae and cyanobacteria are investigated for compounds that may relate to obesity and metabolic phenotypes, yet the evidence base remains scattered and inconsistently reported. We conducted a PRISMA-ScR scoping review of PubMed, Europe PMC, and OpenAlex and mapped eligible full-text studies to a controlled vocabulary covering intervention concepts, mechanistic pathway nodes, and obesity-related outcome domains. Of 2651 reports sought for full text, 936/2651 (35.3%) were not retrieved; therefore, evidence maps should be interpreted as conditioned on full-text accessibility. We included 836 studies and summarized study density (counts only) by population/model tier, mechanistic reporting depth, chemical class, and safety/toxin flags. The literature is concentrated in animal models (485 studies) and human studies (292), with fewer in vitro/ex vivo reports (59). Mechanistic reporting was often limited: 582 studies did not provide extractable mechanistic endpoints, whereas 254 reported biomarker or pathway "anchors". Across intervention concepts, lipid/PUFA, carotenoids, phycobiliproteins, and polysaccharides were most common; within the anchored subset, inflammation (NF-κB), AMPK signaling, adipogenesis (PPARγ-related), and lipogenesis were the most frequently mapped nodes. Together, this evidence map clarifies where mechanistic anchoring and safety documentation are sparse and provides a clear starting point for downstream evaluation.