# Olfactory Capacity and Obesity: A Narrative Review of the Literature
## 3 Results
### Studies in Adults  
[PERSON]'s study [54] included two experiments. The first study showed that odor sensitivity was greater in the unsatiated state compared to the satiated state, particularly in the group with a lower BMI. Conversely, the second study found that participants with a higher BMI exhibited greater sensitivity to food odors when satiated than unsatiated. In contrast, in participants with a lower BMI, there were no differences in odor sensitivity between the two states. In [PERSON] study [39], participants of both sexes with varying BMIs were compared, revealing a decrease in olfactory sensitivity in individuals with a higher BMI. In another study by [PERSON] [55], participants with and without obesity completed a standardized olfactory threshold test for an ecologically valid food-related odor (chocolate). The findings suggested that obese individuals exhibit greater olfactory sensitivity and preference for an odor associated with energy-dense foods (chocolate). In [PERSON]'s study [27], 67 participants with varying BMIs were evaluated for olfactory ability using the Sniffin' Sticks test and a food-associated odor test. Eating behavior measures were also assessed, and the olfactory bulb volume was measured using magnetic resonance imaging (MRI). No association was found between olfactory function and BMI; however, the volume of the olfactory bulb was significantly smaller in obese participants compared to those with normal weight. Additionally, an inverse correlation was observed between olfactory bulb size and BMI. In [PERSON]'s study [56], 221 participants of both sexes were evaluated and categorized into groups of normal weight, overweight, and Grade I and II obesity. Significant reductions were found in total scores and subtest scores for taste and smell in individuals with Grade I and II obesity compared to those with normal weight and overweight. Additionally, the frequency of nutrient intake showed a progressive increase across BMI stages. Significant associations were found between BMI and taste/smell subtests, as well as the intake of sugar, flavor, carbohydrates, saturated fats, monounsaturated fats, and polyunsaturated fats. [PERSON] et al. (2004) reported that morbidly obese patients (\(n=101\), both sexes) with a BMI \(>45\) were more likely to have olfactory dysfunction compared to those with a BMI \(<45\). Specifically, individuals with a higher BMI were significantly more prone to experiencing absolute olfactory dysfunction or anosmia [57]. A study by [PERSON] et al. [58] evaluated the effect of the rs2821557 polymorphism in the human Kv1.3 gene on olfactory function and BMI across different age groups. Additionally, various studies have shown that individuals with olfactory disorders report changes in their eating habits, favoring foods with stronger flavors and higher energy content, such as fats, sugars, spices, and salt, over foods like vegetables, which leads to increased body weight. For example, in a study by [PERSON] et al. [59], 120 women were recruited, nearly half of whom (37 out of 80) had olfactory dysfunction. The following nutritional risk pattern was associated with lower olfactory perception: reduced interest in food-related activities (e.g., enjoying cooking or eating a wide variety of foods); lower preference for foods with sour/bitter flavors (e.g., citrus fruits) or spicy flavors (e.g., horseradish); higher intake of sweets; lower intake of low-fat dairy products; and a nutrient intake profile indicative of a higher risk of heart disease. In the study by [PERSON] et al. [12], participants with quantitative olfactory impairment and control participants were recruited. They were asked to identify odors and rate them in terms of intensity, pleasantness, familiarity, irritation, and edibility. The researchers found that participants with reduced olfactory capacity were less attracted to new foods and tended to experience less pleasure while eating.