<p>In light of the rapidly increasing number of people with diabetes worldwide and the resulting surge in medical costs, we have attempted to reassess the effectiveness of inexpensive and readily available balneotherapy on diabetes and obesity by summarizing recent related papers. For this analysis, 22 studies were selected through searches of multiple databases, including MEDLINE, Embase, CENTRAL, Medical Central Journal Web, and Web of Science. The selected studies consisted of 12 full-body baths, six on foot baths, two on saunas, and two on drinking water therapies. Among participants receiving full-body bath therapy, reductions in blood glucose levels and weight loss were reported. Moreover, immersion in hot water at high temperatures appeared to be more effective. In balneotherapy, using water containing solutes was more effective than using plain hot water. Saunas were effective in reducing participants’ blood glucose levels and weight. Hot-spring foot baths were effective for diabetic complications such as peripheral circulatory disorders and peripheral neuropathy. Drinking water containing sulfur or bicarbonate was effective in reducing the blood glucose levels. The previously reported effects of hot-spring therapy on diabetes and obesity were reconfirmed, and it became evident that the solutes present in hot-spring water contributes to its therapeutic effects. However, in the present analysis, only three studies included more than 100 participants. Although larger studies are desirable, hot-spring interventions are not well-suited to large-scale trials requiring uniform conditions. Therefore, it is essential to continue collecting new findings and comprehensively evaluating the therapeutic effects of balneotherapy, as demonstrated in this review.</p>