Nicole Avena

Obesity in the US

The Addiction Model is Appropriate for Use with Food

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In 2012, ~69% of adults in the U.S. were overweight, of which ~35% were obese.

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Being obese or overweight is associated with multiple comorbid health concerns (e.g., heart disease, diabetes).

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Increased body weight can also have psychological, economical, and social consequences.

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The cost of both overweight and obesity in the US was estimated to be $113.9 billion in 2008, 510% of healthcare spending (Tsai et al., 2011).

Nicole M. Avena, Ph.D. New York Obesity Research Center Columbia University

Outline of the Presentation  The problem of obesity  A brief outline of factors thought to contribute to the rise in obesity  Background on food-reward and select associated brain systems

Why are so many people overweight or obese?

 Defining an addiction  Assessment of “food addiction” in laboratory animal models  Points for further discussion

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Nicole Avena

Portion Size and Portion Creep

Obesity is an endpoint, with multiple contributing factors Sedentary lifestyle Genetic disorders (PraderWilli syndrome)

Genetic vulnerability

Food Reward (addiction?)

Obesity Increases in portion sizes

Food accessibility

Stress and endocrine factors

Social norms regarding food

Food Acquisition Is Easier Than It Used To Be What is a food?

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Nicole Avena

Hunger- vs. Hedonically-driven Eating

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Nicole Avena

Could some people be “addicted” to eating highlypalatable foods rich in sweets and fats in ways that resemble drug addiction? Could such out-of-control eating result in increased body weight and obesity in some individuals?

What happens in select parts of the brain when we eat?  Drugs that are abused act on brain systems that reinforce natural behaviors (e.g., sex, feeding).

What is an addiction?

 There are overlaps in the brain regions activated by palatable foods and drugs of abuse.

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Nicole Avena

How Do We Define Addiction?

DSM-V Criteria for Substance Use Disorders Criterion C: Risky Use

The DSM-V describes a substance use disorder as… “a cluster of cognitive, behavioral, and physiological symptoms indicating that the individual continues using the substance despite significant substance-related problems.”

Criterion D: Pharmacological

• Recurrent substance use in situations in which it is physically hazardous

• Tolerance - requiring an increased dose of the substance to achieve the desired effect or a markedly reduced • The individual may continue substance effect with the usual dose use despite knowledge of having a persistent or recurrent physical or • Withdrawal - occurs when blood or psychological problem that is likely to tissue concentrations of a substance have been caused or exacerbated by decline in an individual who had the substance maintained prolonged heavy use of the substance Note: The DSM-V indicates that “for certain classes [of drugs] some symptoms are less salient, and in a few instances not all symptoms apply (e.g., withdrawal symptoms are not specified for inhalant use disorder).

DSM-V Criteria for Substance Use Disorders Criterion A: Impaired Control

• Binge - Taking the substance in larger • Recurrent substance use may result in amounts or over a longer period than a failure to fulfill major role obligations at work, school, or home originally intended • Desire to limit or quit - Persistent desire to cut down or regulate substance use and may report multiple unsuccessful efforts to decrease or discontinue use

• Substance use is continued despite having recurrent social or interpersonal problems caused or exacerbated by the effects of the substance

• Time - A great deal of time is spent obtaining, using, or recovering from the effects of the substance

• Important social, occupational, or recreational activities may be given up or reduced

• Craving - an intense desire or urge for the drug

The Utility of Animal Models

Criterion B: Social Impairment  Allow us to study physical and psychological disorders, and possible treatments, in ways that would otherwise be unfeasible  Allow us to isolate the biological mechanisms associated with a disorder without the influence of potentially confounding variables such as social and cultural influences

Note: animal models provide a method of investigating specific aspects or symptoms, that characterize a disorder.

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Nicole Avena

Bingeing/Tolerance

Rada, Avena, and Hoebel (2005)

Daily Intermittent Sucrose and Chow Daily Ad libitum Sucrose Twice

Added Sugar Consumption in the United States

Added sugar, as measured here, includes: white, brown and raw sugar, syrup, honey, and molasses that were eaten separately or used as ingredients in processed or prepared foods such as breads, cakes, soft drinks, jams, and ice cream.

The National Cancer Institute (2010)

Sucrose and Chow

Alterations in Brain Dopamine Levels •

Increases in dopamine (DA) release wane with repeated exposure to chow; however, these increases continue in response to sugar.

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This effect is only seen in sugar-bingeing rats, not control rats.

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This effect is also seen in response to fat (Liang, Hajnal, & Norgren, 2006).

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Rats are not overweight.

All rats

Binge group

Rada, Avena and Hoebel (2005)

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 Rats prone to overeat are more likely to cross a shock grid to access palatable food (Oswald, Murdaugh, King & Boggiano, 2011). A recent study also found that rats lever pressing for palatable food were more resistant to the effects of punishment (mild foot shock) than rats lever pressing for methamphetamine (Krasnova et al., 2014). •

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Sugar bingeing rats show signs of anxiety when given an opioid antagonist (naloxone), or when fasted from all food for 36 h. Opioid systems are perturbed by overeating, as revealed by increased muopioid receptor binding in these animals prior to withdrawal. Colantuoni et al. (2001); Avena, Bocarsly, et al. (2008)

Neural correlates of withdrawal

 Rats that overeat sugar daily show an increase in intake following a period of abstinence (Avena et al, 2005), and will work harder to access sugar-associated cues (Grimm et al., 2005).

% CHANGE FROM BASELINE

Craving

Withdrawal

30

**

12-h Daily Sugar

25 20 15 10 5 0 -5 -10 -15 -20

30-min Daily Sugar

Cross-sensitization to drugs of abuse **

Locomotor Activity (% of Day 0 beam breaks)

400

Daily Intermittent Sucrose and Chow

350

Daily Intermittent Chow

300 250

Daily Ad libitum Sucrose and Chow

200 150

Daily Ad libitum Chow

100 50

• Sugar-bingeing rats are hyperactive in response to a low dose of amphetamine.

0

Day 1

Day 21

Amph Test (0.5 mg/kg) Day 29

• Sugar-bingeing rats consume more alcohol.

DEPRIVATION

Withdrawal from sugar is concurrent with decreases in dopamine and increases in acetylcholine levels in the nucleus accumbens, similar to the pattern seen during drug withdrawal. Avena, Bocarsly, et al. (2008)

Avena and Hoebel (2003); Avena et al. (2004)

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Nicole Avena

When we have variety… we tend to eat more. Is the construct of food addiction “distracting”?

 A number of studies have revealed that when rats and humans have a variety of foods available to them, they tend to eat significantly more.  One possible reason for this is “sensory specific satiety.”

• Rats with access to a cafeteria-style diet are hyper-responsive to amphetamine in terms of dopamine release.

• However, they do not respond to a lab chow meal. These rats need “junk food” to release accumbens dopamine.

“The danger of adopting a food addiction model is that it diverts attention from the main causes of overeating and obesity” (Rogers, 2013) “…obesity is better viewed as due to a 'toxic' environment” (Rogers, 1999)  Supporting the possible role of food addiction in perpetuating obesity does not preclude the legitimacy of other factors. Rather, food addiction models in the laboratory affirm the importance of the food environment in promoting food addiction.

Geiger et al. (2009)

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Nicole Avena

The “loss of control” does not have to be “extreme” as we typically think of it. The most common addict in our society is a smoker

Food addiction may be fitting for individuals with binge eating disorder, but is it helpful for understanding obesity?

 likely a fully functioning individual  little noticeable intoxication  withdrawal syndrome is not physically life-threatening  However, because of smoking's health-related complications, it is the number 1 cause of preventable death in the U.S.  Addiction to highly-palatable, processed foods may resemble nicotine addiction

“Experts mostly agree that (drug) addiction refers to ‘the extreme or psychopathological state where control over drug use is lost’ (Altman et al, 1996). Such extreme loss of control does perhaps characterize binge eating…However, while binge eating may be thought by some to be an example of food addiction and people with binge eating disorder being more likely than non-binge eaters to be obese, most obese people do not have binge eating disorder. More mundanely, extreme loss of control does not describe at all well the repeated failure to resist energy-rich foods and large portions that gradually contributes to weight gain. This is probably the more typical pathway to obesity.” (Rogers, 2013)

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Does the title of a “food addict” confer stigma?

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Nicole Avena

Summary

Allen et al. (2012)

Thank you! Students: Collaborators: Mark Gold Pedro Rada Sarah Leibowitz

Miriam Bocarsly Susan Murray Alastair Tulloch Monica Gordillo Eric Su Stephanie Yarnell Elyse Powell

Contact: [email protected]

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