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Review
. 2023 Dec 25;14(1):16.
doi: 10.3390/metabo14010016.

The Role of the Olfactory System in Obesity and Metabolism in Humans: A Systematic Review and Meta-Analysis

Lolita Matiashova  1 , Anouk Lisa Hoogkamer  1 , Katharina Timper  1   2
Affiliations
Review

The Role of the Olfactory System in Obesity and Metabolism in Humans: A Systematic Review and Meta-Analysis

Lolita Matiashova et al. Metabolites. .

Abstract

Obesity, linked to chronic diseases, poses a global health challenge. While the role of the olfactory system in energy homeostasis is well-documented in rodents, its role in metabolism regulation and obesity in humans remains understudied. This review examines the interplay between olfactory function and metabolic alterations in human obesity and the effects of bariatric surgery on olfactory capabilities in humans. Adhering to PRISMA guidelines, a systematic review and meta-analysis was conducted, focusing exclusively on original human studies. From 51 articles, 14 were selected for the meta-analysis. It was found that variations in olfactory receptor genes influence the susceptibility to odors and predisposition to weight gain and poor eating habits. Bariatric surgery, particularly sleeve gastrectomy, shows significant improvements in olfactory function (SMD 2.37, 95% CI [0.96, 3.77], I = 92%, p = 0.001), especially regarding the olfactory threshold (SMD -1.65, 95% CI [-3.03, -0.27], I = 81%, p = 0.02). There is a bidirectional relationship between olfactory function and metabolism in humans. Bariatric surgery improves olfactory perception in obese patients, but it is still unclear if impacting the olfactory system directly affects eating behavior and the energy balance. However, these findings open novel avenues for future studies addressing the olfactory system as a novel target to alter systemic metabolism in humans.

Keywords: bariatric surgery outcomes; genetic variations in olfactory receptors; metabolic syndrome; metabolism; obesity; odor; olfactory function; smell; weight management.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Factors Impacting Olfactory Sensory Perception (Created using Adobe Illustrator).
Figure 2
Figure 2
Adapted from PRISMA Flow-Chart 2020 [66].
Figure 3
Figure 3
Changes in olfactory function parameters upon bariatric surgery versus control group. (a) Total TDI, (b) threshold, (c) discrimination, and (d) identification.
Figure 4
Figure 4
Comparison of Roux-en-Y Gastric Bypass (RYGB) versus Sleeve Gastrectomy (SG). Changes in olfactory function according to olfactory identification (TDI).
Figure 4
Figure 4
Comparison of Roux-en-Y Gastric Bypass (RYGB) versus Sleeve Gastrectomy (SG). Changes in olfactory function according to olfactory identification (TDI).
Figure 5
Figure 5
Changes in olfactory function according to visual analogue scale (VAS) score upon Roux-en-Y Gastric Bypass (RYGB) versus Sleeve Gastrectomy (SG).
Figure 6
Figure 6
Risk of bias of the studies investigated.
See this image and copyright information in PMC

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