If you’ve been on social media, you’ve probably seen ads for red light therapy — glowing panels, masks and spa treatments promising everything from fat and weight loss to “optimized cellular function” and boosted “energy”. There are a huge number of devices available, with some sold in pharmacies and big box retailers. Given how popular (and potentially expensive) obesity treatments can be today, it’s perhaps not a surprise that red light therapy is being pitched as a non-drug, non-invasive solution. When I see products like these, my first question is always the same: Is there evidence to support this?
What is Red Light Therapy?
Red light therapy (RLT), or low-level laser therapy (LLLT) (also sometimes called photobiomodulation (PBM)) uses light in the red light (600 – 700nm) or near-infrared (780 – 1000nm) spectrum, usually delivered by LEDs or lasers. Unlike ultraviolet light, which can damage skin, red and near-infrared light penetrate deeper without causing burns. Proponents claim this light stimulates mitochondria – the “powerhouses” of our cells – to produce more energy (ATP), which supposedly improves healing, reduces inflammation, and accelerates fat breakdown. How red light simulates mitochondria is thought to be through interaction with cytochrome c oxidase (CCO), a key enzyme in the mitochondrial electron transport chain. Red and near-infrared light are thought to be absorbed by CCO, displacing nitric oxide (NO), which otherwise blocks mitochondrial respiration.
The idea sounds appealing and astonishingly simple: shine light, energize your cells, and your body performs better. But while this effect on mitochondria has been observed in vitro, in cells in labs, translating that effect into outcomes that we actually care about, like weight loss or some other measure of improved health, is a very different challenge.
Weight Loss Claims
One of the more common promises made by red light therapy manufacturers and influencers is weight loss or just “melting fat.” Advertisements suggest that shining red light on the body can break down fat cells, reduce cellulite, and shrink waistlines without diet or exercise. While some studies do report modest reductions in waist, hip, or abdominal measurements, these conclusions typically come from small, short-duration trials. Some are device-manufacturer-sponsored, and rely on less accurate surrogate measures (e.g., inches lost) rather than direct measures of fat mass or sustained weight change. Risks of bias are high.
A 2025 meta-analysis by Sun et al. pooled 11 randomized controlled trials with 569 participants and reported statistically significant, though modest, improvements in weight (–3.54 kg), BMI (–1.18 units), and waist circumference (–7.28 cm), along with favourable changes in metabolic and inflammatory markers. The authors concluded that RLT may be a promising adjunct for weight management but emphasized the need for larger, longer-duration, and higher-quality studies. Importantly, most of the included trials were small and heterogeneous, so the true clinical relevance remains unclear.
Overall, the evidence for red light therapy as a weight loss intervention remains weak. Apparent effects may reflect temporary fluid shifts, measurement bias, or placebo effects rather than true fat loss. Red light cannot “vaporize” fat – the body has no mechanism to simply eliminate it this way, and metabolism doesn’t work like that.
Regulation and Risks
Red light therapy is generally marketed as safe and noninvasive, and studies report few adverse effects. The most common side effects include mild skin irritation, eye strain, and headaches, particularly if protective eyewear is not used. Longer-term safety after frequent and prolonged exposure has not been as well studied. Ultimately, safety depends on the specific product in use, and how it is used. There are hundreds, if not thousands of products marketed.
Cost, however, is unavoidable. Spas or wellness clinic treatments can cost hundreds, especially if you have multiple sessions. Home devices range from several hundred dollars to several thousand, with no guarantee of durability or clear evidence of effectiveness. Importantly, each product is unique (considering design, power output, and wavelengths) and it’s consequently not possible to extrapolate the findings from one product to another.
Regulation is mixed and depends on the jurisdiction. Where products are cleared for sale by regulators (e.g., the FDA in the United States) it may only be approved for marketing for limited uses like temporary pain relief or improving skin appearance. Claims about fat loss, enhanced performance, or broader health benefits do not appear to have been formally assessed and approved by any regulator. This means much of the marketing surrounding red light therapy stretches well beyond what regulators have evaluated, leaving consumers left to themselves to evaluate the claims.
Trendy, yes. Evidence-informed, no.
Red light therapy is widely promoted as a treatment for many conditions. The evidence for weight loss is not impressive. While some small studies suggest modest improvements in certain measures, the evidence is inconsistent and based on short-term outcomes. As they say, more research is required.
From a first principles perspective, it seems obvious that red light therapy cannot simply “melt fat” or trigger effortless weight loss. Moreover, sustained health changes will be necessary to sustain any temporary effects, even if they are real.
Reassuringly, red light therapy appears safe when used appropriately and carefully. However the long-term risks are less well understood. High costs is a expected side effect, with potentially substantial costs. Until better evidence emerges, I’d put a red light on red light therapy and look at any claims very skeptically.
