Weight Loss, Dietary Preferences, and Reduction in the Sense of Smell with the Use of a Novel Nasal Device

Abstract

<b><i>Introduction:</i></b> Exposure to food odors are known to increase food intake. Olfaction declines from age 50 years. <b><i>Objective:</i></b> We examined changes in the sense of smell, body weight, food preferences, and parameters of metabolic status, following the use of a specially designed nasal device. <b><i>Methods:</i></b> This is a randomized, placebo-controlled study. Participants wore a nasal device (soft silicone insert) for 5–12 h daily (device group) or inserted 2 drops of normal saline into each nostril daily (control group). Follow-up visits occurred every 2 weeks. All participants were given a 500 kcal/day reduced diet and instructed not to change their regular physical activity. Weight, food preferences, olfactory sensitivity, and blood tests were performed at baseline and after 12 weeks. <b><i>Results:</i></b> Of 156 participants, 65 (42%) completed the study. Sense of smell decreased in the device group (from 6.4 ± 0.9 to 4.4 ± 1.5, on a scale of 0–7, <i>p</i> &#x3c; 0.001), and did not change in the control group. Weight loss decreased by 6.6 ± 3.7% (<i>p</i> = 0.001) and by 5.7 ± 3.5% (<i>p</i> = 0.001) in the respective groups (between-group difference, <i>p</i> &#x3e; 0.05). Among participants aged ≤50 years, weight loss was greater in the device than in the control group (7.7 ± 4.2% vs. 4.1 ± 2.9%, <i>p</i> = 0.02). Insulin level and the homeostatic model assessment of insulin resistance (HOMA-IR) were significantly reduced in the device group (<i>p</i> = 0.02 and <i>p</i> = 0.01, respectively), but not in the control group. Food preferences for sugar (<i>p</i> &#x3c; 0.02), sweet beverages (<i>p</i> &#x3c; 0.001), and artificial sweeteners (<i>p</i> &#x3c; 0.02) were significantly reduced in the device group compared to the control group. <b><i>Conclusions:</i></b> The use of a novel self-administrated nasal device led to reduced olfactory sensitivity, improved insulin sensitivity, weight loss, and lesser preference for sweets in adults aged ≤50 years.