Marie-Odile Monneuse

Food neophobia in the context of a varied diet induced by a weight reduction program in massively obese adolescents

Previous studies in humans have shown that short to middle-term pre-exposure to multiple foods can reduce the negative response to novel foods (neophobia). In order to explore the effects of a long-term exposure to varied foods on food neophobia, we studied a population of obese adolescents observed in a longitudinal protocol in which the multiple food experiences are induced by a residential weight reduction program (WRP) that encourages the consumption of a wide variety of foods. Seventy-two massively obese adolescents (22 boys) filled the food neophobia scale (FNS, [Pliner, P., & Hobden, K. (1992). Development of a scale to measure the trait of food neophobia in humans. Appetite 19, 105-120]) and an ad hoc food familiarity and liking questionnaire at the beginning and at the end of the program (mean duration: 8.9 months). Their scores were compared to those of a control group of 51 adolescents (14 boys) tested within a similar period. FNS results show a decrease of food neophobia, without significant difference between the control group and the WRP subjects, although only WRP have encountered new foods experiences as attested by the familiarity and liking results. Methodological considerations, concerning the characteristics of the participants, the nature of the multiple food exposure and the food neophobia measurements, will be proposed to explain differences among studies.

Taste perception in massively obese and in non-obese adolescents

OBJECTIVE The purpose is to determine whether taste functions are different in massively obese adolescents as compared with non-obese adolescents, and to what extent metabolic disorders may interfere with taste perception, as suggested by the results of recent animal studies. RESEARCH METHOD AND PROCEDURES We compared taste sensitivity and hedonic responses of 39 adolescents with severe early onset obesity (mean BMI: 39.5; min-max: 30.9-51.6) and 48 non-obese adolescents (mean BMI: 21.0; min-max: 16.5-27.9) of both sexes. We measured recognition thresholds for fructose, sucrose, citric acid and sodium chloride. Supra-threshold perceived intensity and hedonic responses were assessed for solutions of sucrose and sodium chloride. In obese subjects, the occurrence of the metabolic syndrome was assessed by measuring blood pressure and, in blood samples, fasting glycemia and insulinemia, the concentration of triglycerides and HDL cholesterol. HOMA modelling was used to assess insulin resistance. RESULTS Massively obese adolescents present a higher sensitivity to sucrose and sodium chloride than non-obese adolescents, with significantly lower recognition thresholds, and higher perceived intensities at supra-threshold levels for sucrose and salt. Hedonic responses are significantly lower for sodium chloride in the obese subjects. Among obese subjects, a significant positive correlation between taste responsiveness and the number of obesity-related metabolic disturbances is observed only in girls. CONCLUSION Massively obese subjects have higher taste sensitivity than control subjects, especially for sucrose and salt. This can be explained, to some extent, by the influence of obesity-related metabolic disorders, which appears to be gender-specific.

Taste acuity of obese adolescents and changes in food neophobia and food preferences during a weight reduction session.

The relationship between taste acuity and food neophobia, food familiarity and liking has been studied in the context of a residential weight reduction session (WRS; mean duration: 10 months) in 39 obese adolescents. Taste acuity was assessed using recognition thresholds for sucrose, citric acid, sodium chloride and 6-n propylthiouracil (PROP) and supra-threshold perceived intensities for sucrose, sodium chloride and PROP. Food neophobia was assessed by using the food neophobia scale at the beginning and at the end of the WRS. At these time points we used also a food familiarity and liking questionnaire to assess changes in food familiarity and likes or dislikes for different food categories. Taste acuity appeared to mediate behavioural food-related changes during the WRS. High taste acuity was associated with limited reductions in food neophobia; less sensitive subjects showed greater increases in the acceptability of healthy foods, especially fruits and vegetables. Therefore, taste perception (and particularly PROP perception) appears to be a predictor of the magnitude of food-related behavioural change achieved during a WRS.

Relationship between taste thresholds and hunger under debate

We determined taste recognition thresholds for six compounds (sucrose, fructose, sodium chloride, quinine sulphate, PROP and liquorice) in fasting students and, in the same subjects, after a meal. The testing procedure was the staircase-method in blind conditions. Although taste sensitivity may vary with hormonal status, our results did not show any significant difference in taste recognition thresholds between hunger and satiety. Our Bayesian analysis did not corroborate the hypothesis of increased sensitivity to nutrition-related tastants in the fasting state that was recently supported by data obtained with the two-alternative forced-choice method.

Changes in Food Neophobia and Food Preferences During a Weight Reduction Session: Influence of Taste Acuity on the Individual Trajectory

Food neophobia, the reluctance to taste novel food, is an adaptive food behavior in evolutionary terms with survival advantages. When measured by the declarative Food Neophobia Scale (FNS) it appears as a personality and heritable trait, thus susceptible to reduce the food repertory and to limit food variety consumption. Inducing changes in food neophobia would eventually overcome this risk. Furthermore, we know that PROP (6-n –propylthiouracil, a bitter chemical substance) sensitivity is genetically determined and can be used as a marker for food preference: greater PROP sensitivity is linked to a reduced consumption of vegetable and fruit consumption – as the foods taste bitter – which has health implications, and could lead to obesity. One study has shown a relationship between PROP sensitivity of Tunisian adults and their preferences and attitudes toward food. We investigated a possible mediation of taste acuity, (assessed using recognition thresholds for sucrose, citric acid, sodium chloride, and PROP) and supra-threshold perceived intensities for these substances on food preferences (assessed by food familiarity and liking questionnaire on different food categories) and FNS (assessed by using the FNS score) in the context of a 10-month residential weight reduction session (WRS) in massively obese adolescents. Taste acuity appeared to mediate behavioral food-related changes during the WRS. High taste acuity was associated with limited reduction in food neophobia whereas less sensitive subjects showed greater increase in the acceptability of healthy foods – especially fruits and vegetables – and greater reduction in food neophobia. Therefore, taste perception (and particularly PROP perception) appears to predict the magnitude of food-related behavioral change achieved during a WRS. A possible relation and/or superimposed effect of food neophobia and PROP sensitivity on food preference and food use are discussed. Application of these findings will be taken into consideration to start a diet program for obese subjects.