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.