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

Introduction: Exposure to food odors are known to increase food intake. Olfaction declines from age 50 years.

Objective: 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.

Methods: 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.

Results: 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, p < 0.001), and did not change in the control group. Weight loss decreased by 6.6 ± 3.7% (p = 0.001) and by 5.7 ± 3.5% (p = 0.001) in the respective groups (between-group difference, p > 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%, p = 0.02). Insulin level and the homeostatic model assessment of insulin resistance (HOMA-IR) were significantly reduced in the device group (p = 0.02 and p = 0.01, respectively), but not in the control group. Food preferences for sugar (p < 0.02), sweet beverages (p < 0.001), and artificial sweeteners (p < 0.02) were significantly reduced in the device group compared to the control group.

Conclusions: 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.