Targeting the Gut-brain Axis to Facilitate Weight Loss in High Fat Diet Consumers

Change in saturated fat intake as measured by the ASA24

Saturated fat intake will be measured monthly by the automated self-administered 24-Hour recall (ASA24) for 16 months starting from baseline.Saturated fat intake will be reported in grams.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in total saturated fat intake as measured by 3-day food diaries

Saturated fat intake will be measured monthly by 3-day food diaries for 16 months starting from baseline. The 3-day food diaries will be processed with the Nutrition Data System for Research (NDSR). Saturated fat intake will be reported in grams.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in total fat intake as measured by 3-day food diaries

Fat intake will be measured monthly by 3-day food diaries for 16 months starting from baseline. The 3-day food diaries will be processed with the Nutrition Data System for Research (NDSR). Total fat intake will be reported in grams.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in total saturated fat intake as measured by C-reactive protein

Saturated fat intake will be measured by plasma C-reactive protein in mg/L

Time frame: Baseline, 8 month

Change in brain response to milkshake

The Blood-oxygen-level-dependent response (BOLD) in the dorsal striatum to the taste of milkshake and tasteless stimuli will be measured using a 3T fMRI scanner at baseline for all participants and at month 8 for participants in the intervention group.

Time frame: baseline, 8 month

Change in fat perception with Visual Analogue Scale

Fat perception will be measured with the Visual Analogue Scale. Participants will be asked to sample Jello's and puddings of differing fat concentrations and rate their perceptual attributes at baseline, month 4, month 8, and month 16 The Visual Analogue Scale (VAS) will be used to assess perceptual attributes such as oiliness, fattiness, and creaminess, while accounting for hunger, fullness, thirst, and wanting. The VAS is a horizontal line anchored by 'not at all' at one end and 'extremely' at the other. The scale value of 'not at all' will be 0% and the scale value of 'extremely' will be 100%. Higher values indicate that a subject perceives these attributes as more intense.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in fat perception with General Labeled Magnitude Scale

Fat perception will be measured with the General Labeled Magnitude Scale (GLMS). Participants will be asked to sample Jello's and puddings of differing fat concentrations and rate their perceptual attributes at baseline, month 4, month 8, and month 16 The GLMS will assess intensity perception. The GLMS is a vertical line with quasi-logarithmic spaced labels that start at the bottom 'barely detectable' to 'strongest imaginable' at the top.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in fat preference with Labeled Hedonic Scale

Fat preference will be measured. Participants will be asked to sample Jello's and puddings of differing fat concentrations and rate their hedonic attributes at baseline, month 4, month 8, and month 16 The Labeled Hedonic Scale (LHS) will assess liking. The LHS is a vertical line with quasi-logarithmic spaced labels that start at the bottom with 'most imaginable dislike' and go to 'most imaginable like' at the top, with the label 'neutral' in the middle. The scale value of 'most imaginable dislike' will be -100; the scale value of 'neutral' will be 0; the scale value of 'most imaginable like' will be 100. Higher values indicate greater liking of the sample.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in sensitivity to the long-chain oleic acid C18:1 - measured by a 3-alternative forced choice test

Subjects will be presented with a set of three samples, one test sample with a specific concentration of fat and two control samples. Subjects will be instructed to choose "the odd one out". If the subject chooses incorrectly, the fat concentration of the fatty test sample will be increased in the next set of three samples. If the subject chooses correctly, the next set of three samples will have the fatty test sample would contain the same fat concentration as in the previously correctly identified set with two control samples. This will continue until the subject correctly chooses the fatty test sample three times consecutively.

Time frame: Baseline, 4 month, 8 month, 16 month

Change in sugar perception with General Labeled Magnitude Scale

Sugar perception will be measured with the General Labeled Magnitude Scale. Participants will be asked to sample Jello's and puddings of differing sugar concentrations and rate their perceptual and attributes at baseline, month 4, month 8 , and month 16 The GLMS will assess intensity perception. The GLMS is a vertical line with quasi-logarithmic spaced labels that start at the bottom 'barely detectable' to 'strongest imaginable' at the top.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in sugar preference with Labeled Hedonic Scale

Sugar perception will be measured with the Labeled Hedonic Scale. Participants will be asked to sample Jello's and puddings of differing sugar concentrations and rate their hedonic attributes at baseline, month 4, month 8, and month 16 The LHS will assess liking. The LHS is a vertical line with quasi-logarithmic spaced labels that start at the bottom with 'most imaginable dislike' and go to 'most imaginable like' at the top, with the label 'neutral' in the middle.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in fat concentration preference measured by the Monell forced choice test

Fat concentration preference will be measured by the Monell forced-choice test. Participants will be asked to sample Jello's and puddings of differing fat concentrations at baseline, month 4, month 8 , and month 16. Subjects will be presented with pairs of puddings of varying fat concentrations in a two-series test. Subjects will taste two puddings of different fat concentrations and indicate their preferred pudding. The following pairs of puddings will be presented based on the subject's previous choice. This will continue until selection of the same fat concentration twice relative to both a lower and a higher concentration, or until the lowest or highest concentration is chosen twice consecutively.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in sweet concentration preference measured by the Monell forced choice test

Sweet concentration preference will be measured by the Monell forced-choice test. Participants will be asked to sample Jello's and puddings of differing sugar concentrations at baseline, month 4, month 8 , and month 16. Subjects will be presented with pairs of puddings/Jello's of varying sugar concentrations in a two-series test. Subjects will taste two puddings/Jello's of different sugar concentrations and indicate their preference. The following pairs of puddings/Jello's will be presented based on the subject's previous choice. This will continue until selection of the same sugar concentration twice relative to both a lower and a higher concentration, or until the lowest or highest concentration is chosen twice consecutively.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in food reinforcement with RED-13

The relative reinforcing value of foods will be measured using the Reward-Related Eating (RED-13) Questionnaire. This questionnaire results in a score from 0 as the lowest measure of reward-based eating drive and 36 as the highest.

Time frame: Baseline and 8 month

Change in food reinforcement with Becker DeGroot Markov Auction Task

The relative reinforcing value of foods will be measured using a computerized auction task at baseline and month 8. The relative reinforcing value of foods will be measured with a modified version of the Becker DeGroot Markov Auction task. The outcome measure is willingness to pay, such that higher willingness to pay indicates higher relative reinforcing value of foods.

Time frame: Baseline and 8 month

Change in cognition with Kirby Delay Discounting

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include Kirby Delay Discounting, which measures temporal discounting (tendency for people to prefer small, immediate, monetary rewards over larger, delayed rewards). The steepness of the discounting curve represents the tendency for temporal discounting, such that a more steeply declining curve indicates a tendency to devalue rewards as they become more temporally remote.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in cognition with the Relational Task

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include the Relational Task which measures visual relational processing. The number of correct responses in the relational condition is the outcome measurement, such that more correct responses indicates higher visual relational processing.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in cognition with Penn Progressive Matrices Test

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include the Penn Progressive Matrices Test, which measures fluid intelligence. The number of correct responses is the outcome measurement, such that more correct responses indicates higher fluid intelligence.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in cognition with Oral Reading Recognition Test

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include the Oral Reading Recognition Test, which measures language decoding and reading. The score based on accuracy is the outcome measure, such that a higher score indicates higher language decoding and reading ability.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in cognition with Variable Short Penn Line Orientation Test

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include the Variable Short Penn Line Orientation Test, which measures visuospatial processing. The number of correct responses is the outcome measure, such that a higher number of correct responses indicates higher visuospatial processing ability.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in cognition with Matrix Reasoning Task (Core NMOB)

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include the Core Neuropsychological Measures for Obesity and Diabetes (Core NMOB). Core NMOB includes the Matrix Reasoning task, which reflects general cognitive ability or nonverbal reasoning ability. Accuracy across 35 trials is the outcome measure, such that higher accuracy indicates higher general cognitive ability or nonverbal reasoning ability.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in cognition with Digit Symbol Substitution (Core NMOB)

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include the Core Neuropsychological Measures for Obesity and Diabetes (Core NMOB). Core NMOB includes the Digit Symbol Substitution task, which reflects processing speed. The number of correctly matched symbols, within the administration time (90 seconds) is the outcome measure, such that higher number of correctly matched symbols indicates higher processing speed.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in cognition with Go/No-Go Task (Core NMOB)

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include the Core Neuropsychological Measures for Obesity and Diabetes (Core NMOB). Core NMOB includes the Go/No-Go task, which reflects response inhibition. The sensitivity index (d') and commission error rate is the outcome measure, such that higher d' and lower commission error rates indicate higher response inhibition.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in cognition with Penn Word Memory Test

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include the Penn Word Memory Test, which measures verbal episodic memory. The number of correct responses is the outcome measure, such that a higher number of correct responses indicates higher verbal episodic memory.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in cognition with Dimensional Change Card Sorting (Core NMOB)

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include the Core Neuropsychological Measures for Obesity and Diabetes (Core NMOB). Core NMOB includes the Dimensional Change Card Sorting task, which reflects cognitive flexibility and task-switching ability. The accuracy score is the outcome measure, such that higher accuracy indicates higher cognitive flexibility and task-switching ability.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in cognition with Picture Sequence Memory (Core NMOB)

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include the Core Neuropsychological Measures for Obesity and Diabetes (Core NMOB). Core NMOB includes the Picture Sequence Memory task, which reflects learning and memory. The accuracy score is the outcome measure, such that higher accuracy indicates higher learning and memory abilities.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in cognition with Stockings of Cambridge (SOC) test (CANTAB)

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include the Cambridge Neuropsychological Test Automated Battery (CANTAB). The CANTAB includes the Stockings of Cambridge test, which reflects spatial planning. Outcome measures assess the problem difficulty level reached, mean moves used and thinking time are the outcome measures. Scores will be compared to normative data from age and sex-matched peers.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in cognition with Intra-Extra Dimensional Set Shift test (CANTAB)

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include the Cambridge Neuropsychological Test Automated Battery (CANTAB). The CANTAB includes the Intra-Extra Dimensional Set Shift test, which reflects rule acquisition and reversal. Outcome measures assess the number of errors made, the number of trials completed, the number of stages completed and latency. Scores will be compared to normative data from age and sex-matched peers.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in cognition with delayed non-matching to sample test (CANTAB)

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include the Cambridge Neuropsychological Test Automated Battery (CANTAB). The CANTAB includes the delayed non-matching to sample test, which reflects visuospatial memory. Outcome measures include latency (the participant's speed of response), the number of correct patterns selected and a statistical measure giving the probability of an error after a correct or incorrect response. Scores will be compared to normative data from age and sex-matched peers.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in cognition with Paired Associates Learning task (CANTAB)

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include the Cambridge Neuropsychological Test Automated Battery (CANTAB). The CANTAB includes the Paired Associates Learning task, which assesses episodic memory and new learning. Outcome measures include the errors made by the participant, the number of trials required to locate the pattern(s) correctly, memory scores and stages completed. Scores will be compared to normative data from age and sex-matched peers.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in cognition with Probabilistic-Feedback Reward Task

A neuropsychological test battery will be performed to assess obesity or dopamine-related differences in cognition at baseline, month 4, month 8, and month 16. The neuropsychological test battery will include the Probabilistic-Feedback Reward Task, which assesses the ability to learn from positive and negative outcome. Outcome measures include the number of times a symbol associated with positive feedback is chosen and the number of times a symbol associated with negative feedback is avoided. Scores will be compared to normative data from age and sex-matched peers.

Time frame: Baseline, 4 month, 8 month, and 16 months

Change in resting energy expenditure

Indirect Calorimetry (IC) will be performed to measure fasting resting energy expenditure at baseline and month 8.

Time frame: Baseline and 8 month

Change in respiratory exchange ratio

Indirect Calorimetry (IC) will be performed to measure fasting respiratory exchange ratio at baseline and month 8

Time frame: Baseline and 8 month