Abstract

Obesity is a chronic, relapsing disease characterized by complex perturbations in glucose homeostasis, lipid 
metabolism, adipokine secretion, inflammation and organ-specific function. These changes often precede overt 
clinical complications by years, creating an important window in which early detection and intervention could 
prevent progression to type 2 diabetes, fatty liver disease and cardiovascular events. Conventional diagnostics 
rely on intermittent blood tests that are invasive, inconvenient and poorly suited to continuous risk 
stratification. Nanobiosensors, integrating nanostructured transducers with selective biorecognition elements, 
are emerging as powerful tools for sensitive, real-time and non-invasive monitoring of metabolic biomarkers in 
easily accessible biofluids such as sweat, saliva, tears, urine and exhaled breath. This review summarizes the 
pathophysiological basis of obesity-associated metabolic dysregulation and the rationale for early, non-invasive 
detection. It then discusses design principles and transduction mechanisms of nanobiosensors, including 
electrochemical, optical and plasmonic platforms. Advances in sampling interfaces for sweat, saliva, tears, breath 
and urine are examined, together with state-of-the-art nanobiosensors for glucose, lipids, adipokines and 
inflammatory markers, including multiplex and wearable systems. We highlight integration with mobile health 
technologies, data analytics and multimodal sensing, and critically examine challenges in analytical validation, 
clinical translation, regulation and equity. Finally, future directions are outlined for personalized, continuous 
metabolic risk monitoring using nanobiosensors as a cornerstone of precision obesity care.