Appetite Measurement and Inter-individual Variability
Creators: name: Cheon, Eunjin
Publisher: name: Purdue University Graduate School
Year: 2022
Subjects: Nutritional science
Clinical nutrition
Food chemistry and food sensory science

description: Appetitive sensations are widely viewed as important signals for eating decisions. Intra- and inter-individual variability have been reported in short-term studies, but it is still unknown whether individual differences are consistent over time and, whether individuals at the appetite extremes vary in energy intake. Therefore, a seventeen-week observational study was conducted to examine the stability of appetitive sensations (hunger, fullness, and thirst), implications of individual differences in appetite on energy intake and eating patterns, as well as associations between appetitive sensations and selected individual characteristics (age, gender, BMI). Ninety-seven (90 completers) healthy adults recorded the intensity of their hunger, fullness, and thirst hourly during all waking hours and reported their energy intake for three days at weeks 1, 9 and 17. There were marked and stable inter-individual differences for each sensation over the 17 weeks: hunger (ANOVA, p&lt;0.001, correlation coefficients of ratings between weeks: week 1 vs week 9, r=0.72 (p&lt;0.001), week 1 vs week 17, r=0.67 (p&lt;0.001), week 9 vs week 17, r=0.77 (p&lt;0.001)), fullness (ANOVA, p&lt;0.001, correlation coefficients of ratings between weeks: week 1 vs week 9 r=0.74 (p&lt;0.001), week 1 vs week 17, r=0.71 (p&lt;0.001), week 9 vs week 17, r=0.81 (p&lt;0.001)), and thirst (ANOVA, p&lt;0.001, correlation coefficients of ratings between weeks: week 1 vs week 9 r=0.82 (p&lt;0.001), week 1 vs week 17, r=0.81 (p&lt;0.001), week 9 vs week 17, r=0.88 (p&lt;0.001)). Cross-correlation functions revealed energy intake and eating pattern exerted stronger effects on appetitive sensations than the reverse. However, the absolute effect sizes of the directional effects were small. No robust effects of the studied individual characteristics (gender, age, BMI) were observed. The primary finding is that acute and chronic sensations of hunger, fullness and thirst are stable across individuals, but are poor predictors of energy intake. This dissertation focuses on the study above, but as part of the training experience, two additional studies were conducted. One entailed appetite concept training to improve the validity of appetite measurements. A potential barrier to accurate appetite measurement is low conceptual understanding by study participants and resulting poor sensitivity and accuracy of responses. While each appetitive sensation is independent and has a unique definition, reported similar patterns between appetitive sensations in multiple studies raise questions about whether participants fully comprehend appetite concepts and provide accurate responses. To overcome this potential limitation, appetite concept materials were developed, and two groups of individuals were provided training either with these materials or unrelated sensory information followed by measurement of appetite responses to five different pre-loads. This study terminated early due to the COVID-19 pandemic and thus we cannot draw a conclusion for now due to the limited number of participants. A second study sought to gain insights on the sensory qualities of fatty acids as part of an effort to determine if oral fat detection is based, in part, on gustatory cues. It has been argued that if fat taste is a primary, the sensations imparted by fats should yield unique percepts and these may be determined by fatty acid chain length. In particular, because acids impart a sour taste, free fatty acids may simply be detected as sour. The fat taste study entailed measurement of intensity ratings with or without sour adaptation (to assess sour notes), tongue locations of taste detection, and subjective descriptors of fatty acids. This study examined intensity and quality ratings of NEFA's ranging from C2 to C18. Oral sites and the time course of sensations were also monitored. Given all NEFA contain carboxylic acid moieties capable of donating hydrogen ions, the primary stimulus for sour taste, testing was conducted with and without sour adaptation to explore the contribution of sour taste across the range of NEFA. Short chain NEFA (C2-C6) were rated as predominantly sour, and this was diminished in C2 and C4 by sour adaptation. Medium chain NEFA (C8-C12) were rated as mainly irritating with long chain NEFA (C18) described mostly as bitter. The latter may reflect the lack of “fatty” lexicon to describe the sensation. Short chain NEFA were mostly localized to the anterior tongue and were of rapid onset. The sensation from medium chain NEFA was attributed to the lateral tongue while medium and long chain NEFA sensations were predominantly localized to the back of the tongue and throat and had a longer lag time. The findings indicate there is a systematic transition of NEFA taste quality and irritation with increments in chain length and this is consistent with multiple modes of transduction.