Ingestive Behavior Core (PI: Harry Kissilef, Ph.D.)

Rationale

The Core was established to enable investigators to examine biomarkers, with an emphasis on behaviors that could potentially become phenotypes for control of food intake in humans. Behavioral biomarkers include the size of a meal eaten under controlled conditions, rate of eating, and the report of feelings related to physiological biomarkers such as visceral stimulation by food, the physiological states of organs (e.g. the stomach and intestine), the change in hormone levels, or gastric emptying induced by eating, microstructure of eating (such as licks, swallows, chews, or the overall rate of eating), and indicators of motivation to eat, such as pressing a computer key for food, other items, or money. By providing a controlled laboratory setting for collecting measures of both types of biomarkers, hypotheses could be tested about the mechanisms that underlie normal and disturbed eating behavior, particularly in patients with obesity. Behavioral assessment of eating is a unique aspect of this Core, which has now become routine at the NYORC. As far as we know no other place in the world offers so many services related to ingestive behavior. The behavioral measures constitute a category of "behavioral assay", to quantify such factors as amount consumed in a test meal, or effort expended to get a certain amount of food reward. This core requires a technology just as sophisticated as one conducting molecular analysis. Indeed, behavioral assays, like body composition, or hormone measurements require very specialized equipment and training. The specialized equipment and training needed to set up these measurements is not something that can be done efficiently in every institution

Facilities Available

1. Specialized tables for automatic weighing of food as it is eaten (eating monitors) and recording the weights on a computer for analysis of cumulative intake curves,
2. Pumps that control delivery of food into cups for enforcing a fixed or variable rate of eating
3. Tape recorders and video monitors for instructing and observing subjects during eating.
4. Gamma camera for measuring gastric emptying
5. Facilities for collection of blood during and after eating
6. Facilities for intragastric, intraduodenal and intravenous infusion.
7. (in preparation) A facility for measuring motivation to eat by means of an operant conditioning paradigm and computer controlled pump for delivery of food or fluid reinforcer.
8. Specialized scaling devices for children to rate their feelings and sensations
9. An off site facility, The Substance Use Research Center (SURC) at Columbia Presbyterian, under the supervision of Dr. Richard Foltin, can provide housing and monitoring up to 4 research participants for 24-hr intervals on food intake, eating behavior and related activities.
10. Software for nutrient analysis from food diaries

Activities

The activities of the Core include performance of standardized eating behavior tests and related physiological measurements as well as provision of advice to outside investigators who have funded grants and wish to develop methodology for investigating human eating behavior. In addition, the Core directors will assist users in designing studies that will use the Core laboratory. The laboratory will be available to investigators from other institutions who wish to be trained. Training will also be available for undergraduates, graduate students, post-doctoral fellows and new investigators with K-awards. The laboratory will develop innovated methods for carrying out its major aims as described further below. The laboratory will promote collaborations especially those of a translational nature (i.e. from animal to human, adult to child, and normal to disordered eating behavior).

Services Provided

A. Behavioral Biomarkers

1. Food intake test - The purpose of this test is to measure food consumption under controlled conditions where the rate of eating and amount consumed can be carefully quantified to test hypotheses about the effects of signals and situations that control intake. Subjects are given single or multiple item meals and instructed to eat according to various paradigms, depending on the purpose of the study. Subjects could be asked to binge eat, eat until comfortably satisfied, eat as much as they like, or any other instruction that would involve testing a specific hypothesis. Independent variables for this test can include hormone or nutrient administration by various routes, including oral, intragastric, intraduodenal or intravenous. Simulated naturalistic environments in which ambiance or other environmental variables are manipulated can also be created and intake in such environments measured.
2. Satiation test - This test measures how much food is required for a person to reach a comfortable level of satisfaction with eating, and also the rate at which satiation develops while eating. The individual eats a large fixed amount of food (usually 975 g) and is asked to rate a series of feelings and sensations by means of validated questionnaires after aliquots ranging from 50 to 75 (30 for children) g.
3. Taste test - Subjects are given small portions of foods or fluids (3 to 5 g) and asked to evaluate them using a variety of sensory and hedonic scales. The test is used to classify subjects (for example as PROP tasters or non-tasters) and to serve as covariates for other tests, which may or not be related to eating, such as body composition, hormone levels, weight control status, etc.
4. Controlled eating rate maneuver - The purpose of this maneuver is to test hypotheses about the contribution of rate of eating to amount consumed, and to test the possibility that training subjects to eat at a certain rate might be therapeutic for eating disorders. The subject is asked to eat at a rate that keeps liquid in a small reservoir at a fixed level. As the subject eats, liquid food is pumped into the reservoir at a controlled rate. The subject must eat at the rate predetermined by the pump. The end point can be a subject's intake of the meal, or the amount subjects eat before reporting 'satisfaction' and while they are periodically interrupted as in the satiation test to make ratings of feelings and sensations.
5. Eating motivation test - The purpose of this procedure is to test hypotheses about factors that drive food intake. These could be such factors as the taste and/or type of food, or subject manipulations such as weight loss or surgery. The subject sits in front of a computer screen and presses a key. In response to the key presses, reinforcements are delivered on a predetermined schedule, in the form of actual food or drink, or points that can be exchanged at the end of the session for future food and drink or other reward. The rewarding effect of the reinforcer is determined by the pattern of responding to the various reinforcers on a particular schedule (similar but not identical to "h").
6. Child satiation test - The purpose of this test is to use specially designed scaling devices developed and validated for testing the satiating effects of foods in preschool children. Children are given the device to use both with real foods and with pictures of different types or amounts of foods and asked to rate how they presently, or would, feel after eating or looking at foods
7. Pencil and paper/computer appetite test - The purpose of this test is to measure a subject's desire for a particular type or amount of food without having the subjects actually consume the food. Lines with end-anchors (e.g. none at all extremely) for various feelings and inclinations such as hungry, full, how much you want to eat a meal, a snack, how your stomach feels, tastes in the mouth, etc. will be given to subjects at various points in an experimental manipulation or simply during the day at various time points. A version of this test will be used in conjunction with a computer program under which their choices of portions or types of foods will be measured.
8. Food value motivational test- measures the value of food compared to an alternative of equal monetary worth (either cash or non-food gift items) and the willingness to expend effort to get food or another reinforcer. It is a computer-based task that requires the participant to make a set number of discrete responses on a computer key. The investigator controls the number of responses, the time limit, the number of trials, and the performance schedule. Therefore the task can be used in a progressive ratio format or a fixed ratio format. Responses for each reinforcer vary independently and can be programmed so that one reinforcer is measured under a progressive ratio and one is measured under a fixed or different progressive ratio. Outcome variables available from the program are1) break point for each reinforcer (highest ratio completed), 2) number of responses/reinforcer; 3) rate of response; 4) pause between trials, 5) pattern of reinforcer choices
9. Eating personality tests - The laboratory routinely administers the most widely used tests such as the three factor eating inventory, restrained eating questionnaire, power of foods test (others as requested by Users).
10. Sensitivity and differential discrimination tests for appetite related biomarkers - By using some of the procedures described above (e.g. intake, satiation, pencil and paper) subjects' abilities to sense signals that might be biomarkers for satiation (such as gastric distention and intestinal stimulation by nutrients can be determined. Their abilities will be measured by means of fitting regression lines through responses regressed from stimulation by the putative biomarker. The response line will have both an onset value (i.e, stimulus which is just barely detectable) and a slope with error from which the half discriminated disparity (HDD) can be calculated. HDD is the Weber fraction - 1 and represents the ratio by which the stimulus must be increased for the difference to be detected 50% of the time.
11. Field records of eating - A variety of instruments have been developed for assessing food intake in the field. These include food diaries, food frequency questionnaires, structured interviews, and the like. Tailor-made assessments of eating will also be developed on an as needed basis in collaboration with Core service Users. This service will also include complete nutrient analysis by means of the "Nutrition Data System for Research" software. The following programs are available: Nutritionist 4, Block Food Frequency, Weight by Date Pro, Foodworks (College Edition).
12. 24 monitoring of food Intake- The Substance Use Research Center (SURC) at the Columbia University Medical Center can provide over night monitoring of research participants. Up to 4 research participants can be housed and monitored.

B. Physiological Biomarkers

1. Collection of blood for hormone measurements- Blood is drawn through an intravenous catheter for baseline measurements before, during, and after the subject consumes a fixed liquid test meal with a straw. Blood is drawn at intervals for 1-3 hours. Gastrointestinal hormones can be measured including cholecystokinin, ghrelin, GLP-1. These hormones are assayed by the Hormone and Metabolite Core.
2. Gastric distension- An intragastric balloon attached to a tube is passed into the stomach. Volumetric expansion of the stomach with water or air to different levels can be done prior to or during ingestion of a meal to observe effects on appetite and food intake. Peptide hormones can also be infused to observe the interaction with gastric distension.
3. Gastric emptying- The subject ingests a meal with a radioactive tracer, and the stomach contents are monitored with a gamma camera.
4. Eating under stress test- The purpose of these manipulations is to identify potential phenotypes and test hypotheses regarding stress induced eating behavior. Participants undergo a cold stress test (CPT), which involves placing their non-dominant hand in ice water for 2 minutes. Other paradigms include an interpersonal public speaking task stressor, which entails that participants prepare a 2-minute speech about their negative qualities. They are told they will be giving this speech to a panel of psychology graduate students. From an intravenous line, various hormones, including cortisol, which may mediate the stress-eating relationship, are measured (as described under i - Appetitive Biomarkers above). At 45 minutes following the stress, participants undergo a food intake test (Described in a) above.
5. Collection of blood for hormone measurements- Blood is drawn through an intravenous catheter for baseline measurements before during and after the subject consumes a fixed liquid test meal by straw. Blood is drawn at intervals for 1-3 hours. Gastrointestinal hormones can be measured including cholecystokinin, ghrelin, GLP-1. These hormones are assayed by the hormone and metabolite core.
6. Gastric Distension- An intragastric balloon attached to a tube is passed into the stomach. Volumetric expansion of the stomach with water or air to different levels can be done prior or during ingestion of a meal to observe effects on appetite and food intake. Peptide hormones can also be infused to observe the interaction with gastric distension.
7. Gastric Emptying, The subject ingests a meal with a radioactive tracer, and the stomach contents are monitored with a gamma camera.
8. Eating under Stress test The purpose of these manipulations is to identify potential phenotypes and test hypotheses regarding stress induced eating behavior. Participants undergo a cold stress test (CPT), which involves placing their non-dominant hand in ice water for 2 minutes. Other paradigms include an interpersonal public speaking task stressor, which entails that participants prepare a 2-minute speech about their negative qualities. They are told they will be giving this speech to a panel of psychology graduate students. From an intravenous line, various hormones, including cortisol, which may mediate the stress-eating relationship, are measured (as described under i - Appetitive Biomarkers above). At 45 minutes following the stress, participants undergo a food intake test (Described in a) above.

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