Week 7 RF-Appetite

Question 1

Give an overview of this RF lecture

Answer 1

■ “Balloon belly” (peripheral appetite signalling).
■ “Milkshakes and fake saliva” (central reward systems and cue-
reactivity).
■ “The never-ending bowl of soup” (cognitive control of appetite).
– And manipulating eating rate

Question 2

What are Peripheral Appetite Signals?

Answer 2

1. Stretch receptors in walls of stomach which are triggered by pressure against wall after food
2. Stomach distension - stretch receptors transmit signals via the vagus (afferents) to the hypothalamus.
3. Signals satiation and inhibits food intake.
4. Compensatory response where hypothalamus will signal to stop (negative feedback)

Question 3

What was Geliebter’s (1988) methods on the “Balloon Belly”?

Answer 3

-N = 8 (4 with obesity, 4 lean).

Within-subjects design (6 conditions). Small, standardised breakfast, ingestion of ‘gastric balloon’:
-0mL inflation
-100mL
-200mL
-400mL
-800mL
-800mL inflation followed by immediate deflation
-6 conditions are the inflation ml

-Final condition was to see if a constant pressure was needed or not on stretch receptors to satiate fullness

-Dependent variable: Intake of liquid meal

Question 4

What was Geliebter’s (1988) findings on the “Balloon Belly”?

Answer 4

-The intake of liquid meal was significantly reduced when there was a balloon volume of 400ml or more

-As balloon was inflated the food intake decreases

-Needs to be constant pressure on stretch receptors to see this decrease in food intake

Question 5

What was Geliebter’s (1988) Study 2: differences in stomach capacity by body weight + findings?

Answer 5

-Inflation of balloon in 100mL steps.

-P’s asked to say when it felt uncomfortable (obese people could tolerate longer so have a larger stomach capacity)

-Larger stomach capacity in participants with obesity (relative to lean participants).

-Obese people can consume a larger amount of food until the stretch receptors are triggered

Question 6

What critical analysis is there for Geliebter’s (1988) studies?

Answer 6

-Study isolated effects of stomach distension on appetite, independent of metabolic effect of nutrient ingestion.

-Strengths included within-subjects design and standardisation of appetite at baseline.

-BUT weight-related differences in gastric capacity, metabolic needs, habitual meal size, mean that standardisation might not have been as effective for group comparisons (Study 2).

-Small sample size (8 participants)

-Naturalistic eating conditions?

Question 7

What are the Practical Implications for Geliebter’s (1988) studies?

Answer 7

-Intragastric balloon as a (temporary) therapeutic device to treat obesity.

-But potential for serious adverse events, and questionable efficacy compared to other treatment options (Tate & Geliebter, 2017, Advances in Therapy, 34, 1859-1875).

Question 8

What is the difference between liking and wanting? (Berridge, 1996; Finlayson et al., 2007).

Answer 8

Liking - Affective component - pleasure associated with eating food (may activate but doesn’t require wanting)

Wanting - Motivational component - ‘incentive salience’ (does not require liking)

Question 9

What are some issues in the “Milkshake and fake saliva” study?

Answer 9

-How to measure neural activity in response to food consumption?

-Practical challenge: eating in the scanner

-Control stimulus?

-fMRI is often used in this area of research

-Control was a tasteless liquid with milkshake texture aka ‘fake saliva’

Question 10

What Method was carried out for the “Milkshake and fake saliva” study? Burger & Stice (2013)

Answer 10

-N = 155, standardised appetite.

Measured activity in response to anticipated intake and during intake:
-Attentional regions (visual and medial prefrontal cortices).
-Reward regions (striatum).
-Gustatory and oral somatosensory regions (e.g., anterior insula, postcentral gyrus, opercula).

-2 week energy intake estimated (doubly labelled water).

-standardised appetite=ate before study so everyone’s hunger levels were similar

-anticipated intake=showing pictures of milkshake and/or water (do this as they want to look at cue reactivity)

Question 11

What were the Findings for the “Milkshake and fake saliva” study? Burger & Stice (2013)

Answer 11

Energy intake correlated with increased activity in anticipation of palatable food in:
-Visual cortex (visual processing and attention).
-Frontal operculum (gustatory [taste] cortex).

-No association energy intake and BOLD responses during consumption of palatable food.

Question 12

What is the critical analysis for Burger & Stice’s (2013) study?

Answer 12

-Provides novel evidence re: brain reward and habitual energy intake (not ‘fat mass’ driving effects as in previous studies of participants with or without obesity).

-Objective measure of energy intake.

But, cross-sectional and observational research:
-Experimental manipulation of energy intake (i.e., change energy intake to examine changes in BOLD signals) necessary to disentangle direction of causality.

Question 13

What are the Practical Implications for Burger & Stice’s (2013) study?

Answer 13

Strengthening cognitive control / inhibition of cue reactivity and reward:
-Computerised tasks training inhibition of automatic motivations toward palatable foods as a potential adjunct to weight loss programs (Lawrence et al., 2015, Appetite, 85, 91-103).

Question 14

What is the Cognitive control of appetite? (Rozin et al., 1998)

Answer 14

-How does memory for what we’ve eaten influence satiety?

-Patients with amnesia: Isolating the effect of memory of recent eating from actual ingestion of food.

-E.g., Patient R.H. (from core lecture)

Question 15

What is the “never-ending bowl of soup”? (Rozin et al., 1998)

Answer 15

-Bowl of soup with a tube attached below it via a whole to continually pump soup in or suck soup out (but without making participants aware)

-Manipulates how much people think they’re eating vs what they’ve actually eaten

Question 16

What was Brunstrom et al’s (2012) methods for the “never-ending bowl of soup”?

Answer 16

-Between-subjects design (N = 100).

-2 (perceived soup volume) x 2 (ingested soup volume).

-Hunger rated immediately after, and +1, 2, 3 hours.

-Perceived soup=what they thought they had eaten

-Ingested soup= what they had actually eaten

-Incongruent condition e.g., thought they’d eaten 300ml but actually eaten 500ml

-Congruent condition e.g., thought they’d eaten 300ml and had

Question 17

What was Brunstrom et al’s (2012) findings for the “never-ending bowl of soup”?

Answer 17

-Initially people who had eaten 300ml felt hungrier than 500ml group (no difference than thought and had actually eaten)

-2 hours after P’s who were the most hungry actually ate 500ml rather than 300ml and vice versa

-P’s levels of hunger is more to do with what they thought they had eaten rather than what they actually ate (memory plays a role in satiety)

Question 18

What was the Critical Analysis of Brunstrom et al’s (2012) study?

Answer 18

-Study isolated effects of perceived intake (cognitive influence on satiety) from actual intake.

But…
-No measure of actual food intake.

Episodic memory manipulation confounded with:
-Pre-meal expectations? Disappointment vs satisfaction with portion.
-Eating rate? Eat faster when perceived smaller portion 🡪 weaker satiety response (Wilkinson et al. (2016). PLoS One, 11(2), e0147603).

Question 19

What are the Practical Implications of Brunstrom et al’s (2012) study?

Answer 19

Attentive eating versus distracted eating – impact on meal memory and potential to influence later intake:
-Review of evidence (Robinson et al. (2013) American Journal of Clinical Nutrition, 97(4), 728-742).

Attentive eating advice via a phone app to supplement to weight loss program:
-Robinson et al. (2013). BMC Public Health, 13, 639.

Question 20

How can eating rate be manipulated?

Answer 20

Specific verbal instructions “chew 15 / 40 times per mouthful”
-Impact on satiety hormones (Zhu et al. (2013). British Journal of Nutrition, 110(2), 384-390).

-Instructions + facilitate with spoon size (Andrade et al (2008). Journal of the American Dietetic Association, 108(7), 1186-1191).

-Measure pace and provide real time feedback to increase/decrease speed (Zandian et al.(2012). BMC Public Health, 12, 1-8).

Question 21

What is the Universal Eating Monitor?

Answer 21

-Allows covert monitoring of intake (and eating rate) during meal using concealed scales underneath food tray (Kissileff et al. (1980). American Journal of Physiology, 238(1), R14-R22).

Question 22

How can oral cavity size be manipulated?

Answer 22

-Reduce oral cavity size to reduce bite size and eating rate: McGee et al. (2012). Obesity, 20(1), 126-133.

-A potential intervention (another example of University of Liverpool research!)

Question 23

What is the Overall Summary?

Answer 23

Contribution of varied and innovative research methods to current and ongoing understanding of appetite and weight management:
-“Balloon belly” (peripheral appetite signalling).
-“Milkshakes and fake saliva” (central reward systems and cue-reactivity).
-“The never-ending bowl of soup” (cognitive control of appetite).

-Critical analysis of ‘gaps’ in research methods.

-Practical applications.