De Nardi M. et al. - Photobiomodulation and Energy Metabolism in Obese Women

In a randomized crossover trial, a single 12-minute session of photobiomodulation was followed by a 9.3% increase in resting energy expenditure in 16 obese women. The effect was acute, measured immediately after exposure in a very small sample size, and no body weight data were reported.

What this study measured

Massimo De Nardi and his colleagues conducted a randomized, intra-subject crossover trial, published in *Nutrients* in 2025. Two groups were compared: 16 obese women (age 43 ± 5 years, body mass index 36 ± 4 kg/m²) and 16 sedentary women of normal weight (age 43 ± 5 years, body mass index 22.7 ± 2 kg/m²). Each participant received one photobiomodulation treatment and one sham treatment.

The exposure lasted 12 minutes and covered the front and then the back of the body, using red light (633–660 nm) and near-infrared light (850–940 nm). The primary outcome measure was resting energy expenditure, measured by indirect calorimetry before and after the treatment. Diet and physical activity were controlled. Important point: the light was applied at rest, without any associated physical exercise, which links the observed effect solely to light exposure.

Key Findings

The values reported in the summary are as follows.

• Group × Time Interaction: F = 3.054, p = 0.03
• Main effect of time: F = 10.88, p = 0.001
• Dépense énergétique de repos chez les femmes en situation d’obésité : +9,3 %, soit 1624 ± 314 kcal/jour après photobiomodulation contre 1486 ± 327 kcal/jour avant (p < 0,001)
• Respiratory quotient: no change, so no change in the oxidized substrate
• Perceived exertion: decreased in both groups
• Flexibility: Improvement in Both Groups
• Skin temperatures: a significant increase, more pronounced on the back than on the front

The summary does not provide confidence intervals or a specific value for the normal-weight group.

How Photobiomodulation Affects Metabolism

The proposed mechanism remains hypothetical. Red and near-infrared light is thought to be absorbed by cytochrome c oxidase, the final complex in the mitochondrial respiratory chain, which could facilitate the production of adenosine triphosphate. In skeletal muscle, which is rich in mitochondria, improved mitochondrial function could alter energy expenditure at rest. An effect on oxidative stress and on the low-grade inflammation associated with obesity is also suggested. The study measured an overall metabolic outcome, not the intermediate biochemical steps.

Limits You Should Know

The sample size is very small: 32 women, 16 of whom were in the obesity group. This is a single study, not a meta-analysis, which precludes any generalizations; the authors describe their results as preliminary. The effect is acute, measured after a single session: there is no indication that it persists. Neither weight, body fat, nor body composition were monitored over time. The increase in skin temperature raises the question of a thermal contribution, which the abstract does not allow us to determine. Finally, the study population is limited to middle-aged women.

What This Means in Practice

Not much at this stage. A temporary increase in resting energy expenditure, measured immediately after a session, does not constitute a weight management method. Photobiomodulation is not a substitute for nutritional management, appropriate physical activity, or prescribed treatment. Under no circumstances does it replace antidiabetic treatment: any changes to treatment must be made exclusively by a doctor. For people with diabetes, self-monitoring of blood glucose levels remains necessary, as fluctuations in blood glucose levels have been reported elsewhere following exposure.

Frequently Asked Questions

Does photobiomodulation help with weight loss?

This study does not support that conclusion. It measured an increase in resting energy expenditure immediately after a workout, not a change in weight or body fat. No weight data is included in the abstract. Extrapolating these findings to suggest weight loss would be a misinterpretation of the published results.

What wavelengths and durations were used?

Each session lasted 12 minutes and consisted of a single exposure covering the front and then the back of the body. The wavelengths used were red (between 633 and 660 nm) and near-infrared (between 850 and 940 nm). No physical exercise was included in the protocol.

Why does this effect occur only in obese women?

The abstract reports a significant group × time interaction, indicating a different response depending on the group, without providing an explanation for this. The hypothesis that mitochondrial function was initially more impaired is plausible, though it is not demonstrated here.

Reference

De Nardi M, Allemano S, Buratti M, Conti E, Filipas L, Gotti D, Luzi L, Codella R. Photobiomodulation Acutely Augments Resting Metabolism in Women with Obesity. Nutrients, 2025;17(21):3357. PMID 41228430. DOI 10.3390/nu17213357. https://pubmed.ncbi.nlm.nih.gov/41228430/

This summary is provided for informational purposes only and does not constitute medical advice. Photobiomodulation is not a substitute for prescribed treatment. Consult a healthcare professional.