Endogenous Opioids May be Driving Obesity

Obesity: A Multi-factorial Pathology

Obesity is a multi-factorial pathology, which creates many physiological compensatory mechanisms which result in disease. Its also a pathology which is rooted in many causal components that feed into a cycle of continued behavior which supports the pathology. From neuropsychology, to the gut microbiome, there are many facets of the obesity epidemic to take into consideration. In recent medical research news, the endogenous opioid system was center stage, as researchers looked at how opioid receptor activation is influenced and influences appetite.1

Researchers Used (PET) to View How Feeding is Related to Hedonia-dependent Endogenous Opioid Release

The endogenous opioid system is related to a lot of functions of appetite and has also been implicated in hedonic elements of eating, which contribute to obesity. The current study used positron emission tomography (PET) to look at how feeding is related to hedonia-dependent endogenous opioid release in humans.

The Study

Ten healthy men participated in the study. They were scanned at 3 different times. Once, after a 10 hour fasting period, after eating a palatable meal (pizza), and after eating a non-palatable meal (a nutritional drink). The scans revealed opioid receptor activation with both meals, however, interestingly, opioid receptor activation was more pronounced with the non-palatable nutritional drink. This may indicate a stronger homeostatic mechanism of endogenous opioid release in terms of appetite regulation. The activation of opioid receptors after feeding was independent of subjective hedonic responses to the meal. This suggests both a hedonic and homeostatic mechanism of endogenous opioid release. With increased opioid release there was a decrease in feeding triggered hedonia.

Study Suggests Possible Mechanism Involving Endogenous Opioid System Perpetuates Overfeeding

This research suggests that there may be a mechanism involving the endogenous opioid system that perpetuates overfeeding, leading to obesity. A possible theory is that continuous overfeeding desensitizes the endogenous opioid system, leading to a dysregulated homeopathic response to feeding and less appropriate satiety signals. This is a direction the research team is pursuing in terms of future treatments for obesity.


  1. Tuulari JJ, Tuominen L, De boer FE, et al. Feeding Releases Endogenous Opioids in Humans. J Neurosci. 2017;37(34):8284-8291.
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Node Smith, ND, is a naturopathic physician in Portland, OR and associate editor for NDNR. He has been instrumental in maintaining a firm connection to the philosophy and heritage of naturopathic medicine among the next generation of docs. He helped found the first multi-generational experiential retreat, which brings elders, alumni, and students together for a weekend camp-out where naturopathic medicine and medical philosophy are experienced in nature. Four years ago he helped found the non-profit, Association for Naturopathic ReVitalization (ANR), for which he serves as the board chairman. ANR has a mission to inspire health practitioners to embody the naturopathic principles through experiential education. Node also has a firm belief that the next era of naturopathic medicine will see a resurgence of in-patient facilities which use fasting, earthing, hydrotherapy and homeopathy to bring people back from chronic diseases of modern living; he is involved in numerous conversations and projects to bring about this vision.

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