Hydrotherapy for Overweight and Obesity: A Systematic Review of Anthropometric and Lipid Outcomes

Overweight and obesity are chronic metabolic conditions associated with excess adiposity, impaired physical function, dyslipidemia, and increased cardiometabolic risk. Among hydrotherapy-based modalities, structured aquatic exercise may provide a low-impact exercise option by reducing weight-bearing joint loading, providing water resistance, and facilitating exercise participation, whereas passive hydrothermal interventions and hydrogen-rich water involve different therapeutic mechanisms. This systematic review evaluated the effects of hydrotherapy-based and water-based interventions on anthropometric and lipid profile outcomes in individuals with overweight or obesity. A systematic search was conducted in the Cochrane Central Register of Controlled Trials (CENTRAL), Google Scholar, MEDLINE, PubMed, and Scopus as the main sources, with Web of Science and ScienceDirect as additional sources. MEDLINE and PubMed were retained as separately named prespecified search sources despite their substantial overlap. Searches were conducted without time limits during the registered review period from June 23 to July 31, 2026. Published English-language human intervention studies were eligible if they evaluated hydrotherapy, aquatic exercise, aqua aerobics, water-based aerobic training, aquatic high-intensity interval training, balneotherapy, sauna-based therapy, steam bath, dry sauna, immersion-based therapy, or hydrogen-rich water and reported at least one extractable anthropometric or lipid outcome. Ten studies were included in the qualitative synthesis. Active water-based exercise interventions showed the most consistent pattern of improvement in body weight, body mass index, waist-related measures, body fat percentage, and fat mass. In one randomized double-blind placebo-controlled study, hydrogen-rich water was associated with reductions in body mass index, waist-to-hip ratio, total cholesterol, and triglycerides. Passive hydrothermal interventions showed more variable anthropometric and lipid findings. Reported safety findings were generally reassuring, although adverse-event, adherence, and withdrawal reporting was inconsistent. Hydrotherapy-based interventions may have a complementary role in obesity management. Within the available evidence, structured active aquatic exercise demonstrated the most consistent pattern of anthropometric improvement; however, the certainty of evidence across most outcome domains was low to low-to-moderate, warranting cautious interpretation.