Food reinforcement and obesity

Transcription

1 Food reinforcement and obesity Leonard H. Epstein SUNY Distinguished Professor of Pediatrics and Social and Preventive Medicine School of Medicine and Biomedical Sciences University at Buffalo

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4 Behavioral Economics ❿ Studying food reinforcement involves understanding motivational factors that influence the choice to eat ❿ Behavioral economics, or behavioral choice theory, involves understanding factors that influence choice between two or more alternatives 4

5 Overview ❿Defining food reinforcement ❿How reinforcing is food? ❿Food reinforcement, energy intake and obesity ❿Factors that moderate food reinforcement and eating ❿Food reinforcement and weight loss ❿Concordant dopamine genetics and parent-child weight loss 5

6 Definition of food reinforcement 6

7 Food Reinforcement ❿ The reinforcing value of food, or reinforcer efficacy, describes how hard someone will work to get access to food. ❿ The reinforcing value of food represents one aspect of the motivation to eat ❿ Other related (but not the same) definitions include reward, incentive salience, hedonics, wanting

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9 Hypothetical demand for food Omax 100 Inelastic Elastic Calories Consumed Responses Per Session Pmax 100 Hypothetical Demand Curve Output Function Fixed Ratio 9

10 How powerful a reinforcer is food? 10

11 Elsmore, T. F., Fletcher, G. V., Conrad, D. G., & Sodetz, F. J. (1980). Reduction of heroin intake in baboons by an economic constraint. Pharmacology, Biochemistry and Behavior, 13,

12 Christensen, Kohut, Handler, Silberberg & Riley. (2009). Demand for food and cocaine in Fisher and Lewis rats. Behavioral Neuroscience, 123,

13 Comparison of Essential Values Reinforcer 1/α Food 1230 Food 1/3 Free 885 Alfentanil/Remi. 872 Cocaine 796 Fentanyl 549 Food 2/3 Free 364 Methohexital 329 Nalbuphine 246 Saccharin 126

14 Food reinforcement and obesity 14

15 Reinforcing value of food ❿ 1000 s s of studies have used food as a reinforcer to understand basic mechanisms of learning,, and the neurobiology of food as a reinforcer ❿ Subjects who find food more reinforcing consume more food in ad lib eating situations (Epstein et al 2004). ❿ Food is more reinforcing for obese vs. non-obese obese subjects (Saelens and Epstein 1996, Temple et al, 2008). ❿ Food reinforcement phenotype reliable (test-retrest r >.80) ❿ Reinforcing value sensitizes over time for obese subjects (Temple et al, 2009, Clark et al, 2010) ❿ Food reinforcement predicts weight gain Lean children who find food more reinforcing gain more weight than lean children who do not find food as reinforcing (Hill, Saxton, Webber, Blundell, Wardle, 2009). 15

16 General paradigm for studying food reinforcement and genetics of food reinforcement ❿ Food reinforcement studied during a progressive ratio schedule of reinforcement task Can be single or concurrent schedules ❿ Concurrent schedules provide alternatives ❿ Ad lib eating for high energy dense, palatable snack foods studied in separate session ❿ Subjects provided preload prior to either session This reduces eating just due to hunger, as reinforcer deprivation will increase reinforcing value Enables study of hedonic,, rather than homeostatic hunger ❿ Saliva collected for genetic analysis 16

17 Effect of food reinforcement on energy intake Energy intake by food reinforcement group Energy intake (kcal) Low High Reinforcement group Epstein, Temple, Neaderhiser, Salis, Erbe, & Leddy (2007). Food reinforcement, the dopamine D2 receptor genotype and energy intake in obese and non-obese humans. Behav Neurosci 2007;121:

18 Obese Adults Find Food More Reinforcing than Non-Obese Number of Button Presses Non-obese (n=45) * Obese (n=29) Epstein, Temple, Neaderhiser, Salis, Erbe, & Leddy (2007). Food reinforcement, the dopamine D2 receptor genotype and energy intake in obese and non-obese humans. Behav Neurosci 2007;121:

19 Obese children find pizza more reinforcing than non-obese obese children 20 overweight, 25 non-overweight 8-12 year-old children Responses for food A. B Non-Overweight (n=25) Overweight (n=20) Energy Consumed (KCal) * Schedules of reinforcement 0 Non-overweight Overweight Temple, Legierski, Giacomelli, Salvy & Epstein. (2008). Overweight children find food more reinforcing and consume more energy than nonoverweight children. American Journal of Clinical Nutrition, 87,

20 Overweight children find snack foods more reinforcing than lean children 23 overweight, 22 nonoverweight 8-12 year-old children Choice of snack foods or video games, mazes, word searchers, magazines Non-Overweight Overweight Number of Button Presses Food Non-Food Alternative Schedule of Reinforcement Temple, Legierski, Giacomelli, Salvy & Epstein. (2008). Overweight children find food more reinforcing and consume more energy than nonoverweight children. American Journal of Clinical Nutrition, 87,

21 Reinforcing value of food predicts weight gain in adults over 12 months 2.5 p = p = Weight Change (kg) BMI Change Low FR High FR -0.4 Low FR High FR N = 32 N = 46 N = 32 N = 46

22 The relationship between food reinforcement and weight is mediated by usual energy intake Usual energy intake (FFQ) R = 0.47, p < 0.01 R = 0.26, p < 0.05 RRV foo d R = 0.26, p < 0.05 BMI Controlling for usual energy intake, relationship between RRV food and BMI is not significant, p > 0.05

23 Food reinforcement and sugar ❿ In preclinical animal research, animals will work for access to sugar, animals will binge on sugar, and sugar sensitizes animals to the self-administer drugs of abuse (Avena, 2008). Alcohol, amphetamines and opiods ❿ Using a dataset with 273 participants that included food reinforcement and laboratory energy intake of a sample of palatable foods that vary in fat, carbohydrates, protein and total sugar, we examined which component of food was the strongest predictor of food reinforcement Controlling for the other macronutrients ❿ Each macronutrient was related to food reinforcement, but when controlling for the other macronutrients,, only sugar was an independent predictor of the relative reinforcing value of food

24 250 Sugar energy intake (kcal) <0.2 >2 and <0.5 >0.5 Proportion of responding for food versus reading Epstein, L.H., Carr, K.A., Lin, H., & Fletcher, K.D. (In press).. Food reinforcement, energy intake and macronutrient choice. American Journal of Clinical Nutrition.

25 Impulsivity and Obesity ❿ Impulsivity in young children predicts weight gain (Francis & Susman, 2009; Seeyave et al., 2009). ❿ Impulsivity is related to obesity in women (Nederkoorn, Smulders, Havermans, Roefs, & Jansen, 2006; Weller, Cook, Avsar & Cox JE, 2008) and children (Guerrieri, Nederkoorn, & Jansen, 2008). ❿ Impulsivity is related to food purchases (Nederkoorn, Guerrieri, Havermans, Roefs, & Jansen, 2009). ❿ Impulsive children benefit less from obesity treatment (Nederkoorn, Jansen, Mulkens, & Jansen, 2007).

26 Combining reinforcing value and impulsivity as factors that influence energy intake ❿ Drug addiction is often conceptualized as a function of excessive reward from drugs paired with failure of executive function inhibitory function. We have called this REINFORCEMENT PATHOLOGY (Epstein, Bickel et al, 2010) ❿ This theoretical approach has also been applied to eating in a number of theoretical papers, but this hypothesis remains to be tested ❿ To test this, we studied 28 non-obese obese females Measured delay discounting of money, Food reinforcement, Ad libitum eating.

27 Impulsivity moderates the effect of food reinforcement on energy intake 1100 High delay discounting Low delay discounting Total energy intake (kcal) Low High Food Reinforcement Rollins BY, Dearing KK, Epstein LH. (2010). Delay discounting moderates the effect of food reinforcement on energy intake among non-obese women. Appetite, 55:

28 Dietary disinhibition, food reinforcement, eating and obesity ❿ Disinhibition is associated with tendency to overeat in obesogenic environments. ❿ Disinhibition is related to current BMI, food consumption,and prospective weight gain (Bryant, King, Blundell, 2008). ❿ Disinhibition is related to impulsivity (Yeomans, Leitch, Mobini, 2008). ❿ Using the dataset of 273 participants we explored the relationship between food reinforcement, dietary disinhibition, energy intake and body weight.

29 34 Effect of Dietary Disinhibition on BMI 32 *p < * BMI Disinhibition <6 >6

30 RRVfood Dietary Disinhibition p = BMI RRVfood <32 >32 <32 >32 Disinhibition <6 <6 >6 >6

31 Does food reinforcement predict weight change in child behavioral weight control program? ❿ 241 families with an overweight year-old child were studied in a family-based weight control program for 4 months, and then randomized to 2 different maintenance procedures. ❿ Food reinforcement and availability of alternative non-snack food reinforcers was assessed at baseline.

32 Percent overweight change (0-4 month) Low High Level of non-snack food reinforcers in the environment Low food reinforcement High food reinforcement 32

33 Dopamine, dopamine genetics and food reinforcement 33

34 Dopamine ❿ Dopamine modulates the reward value of food, drink, sexual behavior, social reinforcers, and drugs of abuse (Berrige & Robinson 1998; Martel P 1996). ❿ Dopamine increases in the striatum of animals and humans during both food expectation (Volkow ND 2002) and food consumption (Volkow ND 2002). ❿ Striatal dopamine is crucial to maintaining caloric requirements for an animal s s survival (Szczypka MS 2001). ❿ Nucleus accumbens dopamine is crucial to the rewarding properties of food (Szczypka MS 2001).

35 Dopamine Genetics ❿ Release, reuptake and receptor binding determine brain dopamine activity, which is influenced in part by genetics ❿ We are studying a full range of dopamine genes that could influence dopaminergic activity, including: Synthesis (tyrosine hydroxylase) Transport (SCL6A3 or DAT1) Receptors (DRD1 - DRD5) Breakdown (monoamine oxidase (Mao-a); a); catechol-o- methyltransferase (COMT) And non-dopamine genes, including opiod, serotonin, FTO and melanocortion 4 polymorphisms. ❿ Rapid dopamine transport and/or reduced dopamine binding to D2 receptors may be associated with addictive behaviors, increased eating, and obesity (Wang, Volkow et al 2001; Epstein et al 2002)

36 Dopamine Receptors ❿ D1 class and D2 class receptors ❿ D1 like (D1 & D5) receptors are excitatory, D2 like (D2, D3, D4) receptors inhibitory ❿ Concentration of D1 and D2 receptors times D3- D5 receptors ❿ DRD 2 gene codes for D2 receptors. ❿ A1 allele = lower density D2 s s (reduced( dopamine signaling) ❿ A1/A1, A1/A2 and A2/A2. ❿ A1 allele associated with obesity (Noble et al 1994; Wang et al 2001). ❿ A1 allele associated with activation of brain reward centers (Stice et al., 2009)

37 Individuals with the Taq 1 A1 Allele of the t DRD2 genotype have increased food reinforcement DRD2 Genotype 157 subjects studied, 69 obese, 88 nonobese A2/A2 N = 99 A1/A1 & A1/A2 N = Responses A1 allele is related to fewer D2 receptors FR Schedules of reinforcement

38 Obese Individuals with the Taq 1 A1 Allele Have the Highest Levels of Food Reinforcement Number of Button Presses Non-Obese/A2/A2 (n=25) Non-Obese/A1/A1 or A1/A2 (n=20) Obese/A2/A2 (n=12) Obese/A1/A1 or A1/A2 (n=17) * * * Total Button Presses A2/A2 * A1/A1 or A1/A Non-Obese Obese Epstein, Temple, Neaderhiser, Salis, Erbe, & Leddy, (2007). Food reinforcement, the dopamine D2 receptor genotype and energy intake in obese and non-obese humans. Behavioral Neuroscience, 121,

39 Taq 1 A1 Interacts with Food Reinforcement 1000 to Increase Energy Intake A2/A2 A1/A2 or A1/A1 Energy Consumed (KCal) Low High Food Reinforcement Level Epstein, Temple, Neaderhiser, Salis, Erbe, & Leddy, (2007). Food reinforcement, the dopamine D2 receptor genotype and energy intake in obese and non-obese humans. Behavioral Neuroscience, 121,

40 Does concordance of parent/child DRD2 Taq1 genes relate to similarity of weight loss? ❿ Parent and child weight loss are correlated in family-based behavioral weight loss programs that target parent and child Observed up to five years after treatment In current study, correlations between child and parent zbmi changes at 6 and 12 months were 0.69 and ❿ We have observed significant relationships between parent and child food reinforcement ❿ 26 families with obese parents and obese year-old children were studied. ❿ Families were coded as to whether the parent and child had the same number of DRD2 Taq1 alleles. 15 concordant, 11 discordant

41 Change at 6 Months Change at 12 Months Discordant for Taq1 A1 alleles Concordant for Taq1 A1 alleles Child zbmi Change Child zbmi Change Parent 0-6 zbmi Change Parent 0-1 zbmi Change If CONCORDANT parent/child zbmi changes of 0.78 and 0.89 at 6 and 12 months (p s < 0.001). If parents were at least moderately successful in weight loss (> 1 SD above mean zbmi change), children showed double the change in zbmi at six months (-.352 vs -.175) and over four times the change at twelve months (-.466 vs -.109). Epstein LH, Dearing KK, Erbe RW. Parent-child concordance of Taq1 A1 allele predicts similarity of parent-child weight loss in behavioral family-based treatment programs. Appetite; 2010, 55:

42 Summary ❿ THE MOTIVATION TO EAT IS AN IMPORTANT DETERMINANT OF OVEREATING AND OBESITY Food reinforcement is related to energy intake Food reinforcement is related to obesity Food reinforcement sensitizes over time The influence of food reinforcement on energy intake and BMI is moderated by impulsivity and disinhibition Food reinforcement may predict weight gain Food reinforcement may predict weight loss Dopamine genetics are related to food reinforcement and energy intake Sharing dopamine genetics (and possibly the food reinforcement phenotype) may be a mechanism for the similarity in parent/child weight loss in behavioral obesity programs

43 Acknowledgements ❿ Jim Roemmich, Ph.D. ❿ Brian Saelens, Ph.D. ❿ Jenn Temple, Ph.D. ❿ Kelly Dearing Fletcher, M.P.H. ❿ Rocco Paluch, M.S. ❿ John Leddy, M.D. ❿ Robbert Salis, M.D. ❿ Richard Erbe, M.D. ❿ Myles Faith, Ph.D. ❿ Henry Lin, B.S ❿ Katelyn Carr, B.S. ❿ Oreo Cookie Blues, Lonnie Mack, Strike Like Lightning,