Photobiomodulation Acutely Augments Resting Metabolism in Women with Obesity

Background/Objectives: Photobiomodulation (PBM) is a non-invasive, low-level laser treatment shown to improve insulin resistance, glucose metabolism, and obesity-related inflammation. This study examined whether PBM could acutely enhance mitochondrial efficiency and energy metabolism in women with obesity. Methods: In a randomized, crossover within-subject design, 16 women with obesity (43 ± 5 years; BMI: 36 ± 4 kg/m²) and 16 sedentary normal-weight women (43 ± 5 years; BMI: 22.7 ± 2 kg/m²) underwent PBM (front and back exposure; red light, 633-660 nm; NIR, 850-940 nm) and a sham stimulation (SHAM), as a control, for 12 min. Resting energy expenditure (REE) was assessed via indirect calorimetry before and after exposure. Secondary measures included skin autofluorescence, heart rate, blood pressure, profile of mood states, rate of perceived exertion (RPE), and flexibility. Diet and physical activity were controlled. Results: A 2 × 2 × 2 ANOVA revealed a significant group × time interaction (F_3,60 = 3.054, p = 0.03) and a main effect of time (F_1,60 = 10.88, p = 0.001). Women with obesity showed a significant increase in REE post-PBM compared to pre-PBM (+9.3%, 1624 ± 314 vs. 1486 ± 327 kcal/day; p < 0.001), with no change in the respiratory exchange ratio. Additionally, RPE decreased and flexibility improved in both groups following PBM. Front and back skin temperatures increased significantly post-PBM, with greater changes observed in the back versus the front. Conclusions: These preliminary findings indicate that PBM acutely enhances energy utilization efficiency in women with obesity, increasing resting energy expenditure without modifying substrate oxidation. PBM may represent a promising non-invasive adjunctive strategy for improving the metabolic health of obese individuals.