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Rethinking Leptin Resistance: Why Junk Light and Indoor Living May Be Driving Metabolic Dysfunction



Emerging research suggests that leptin resistance is not solely a consequence of obesity or chronic inflammation - it may be driven by disrupted hypothalamic signalling, rooted in circadian misalignment and inadequate exposure to natural light.



Leptin acts centrally through the arcuate nucleus of the hypothalamus, where it stimulates pro-opiomelanocortin (POMC) neurons to release alpha-melanocyte stimulating hormone (alpha-MSH). This peptide plays a pivotal role in appetite regulation, thermogenesis, and neuroimmune balance via melanocortin-4 receptor (MC4R) pathways (Schwartz et al., 2000; Myers et al., 2009).



However, this leptin - POMC–MSH axis is not autonomous. It is entrained by wavelength-specific circadian input, particularly blue-enriched light (460–480 nm) in the early part of the day. These signals act via melanopsin-containing retinal ganglion cells to synchronise the suprachiasmatic nucleus (SCN) and downstream hypothalamic circuits governing metabolic rhythms (Buijs et al., 2003; Bedrosian & Nelson, 2017).



When this input is absent, as in modern indoor environments dominated by artificial, low-intensity lighting and prolonged screen exposure - circadian gene expression is disrupted. POMC neuronal sensitivity declines, and leptin signalling becomes impaired, even in the presence of normal or elevated circulating levels (Kalsbeek et al., 2011; Wright et al., 2013).



Compounding this, chronic exposure to artificial blue light in the evening further disrupts melatonin production and downstream hormonal timing. The result is central leptin resistance, blunted satiety signals, energy misallocation, and low-grade inflammation.



From a functional medicine perspective, this repositions leptin resistance as not simply a biochemical or dietary issue, but a neurological and environmental one. Sitting under artificial light, detached from solar cues, disrupts the very hypothalamic circuitry designed to regulate energy balance.



Restoring light hygiene through early daylight exposure, reduction of evening screen use, and consideration of near-infrared light for hypothalamic support may be as fundamental to metabolic repair as any dietary or supplement intervention.



Lauren Wallis BSc MSc DipCLN


Functional Medicine Nutritionist | IFM Certified Health Coach













 
 
 

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