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Critical Thinking in Global Challenges

Week 4

Global challenge focus: Obesity, Dr John Menzies

Greetings MOOCers and welcome to the introductory talk on the second topic related to the

challenge of obesity. This week we are going to address the concept of food addiction, the

idea that the high levels of obesity we see in our modern society may be driven, at least in

part, by an uncontrolled compulsion to eat. A desire to eat that is analogous to a drug

addicts desire to use a drug.

We saw in last weeks session that the prevalence of obesity has been steadily increasing

over the past few decades and I mentioned the simple idea that obesity is driven by

overeating. One notable thing, in Western countries at least, is that the increase in obesity

has been accompanied by an increase in food availability. But this does not directly explain

obesity, just because more food is available and it has become relatively cheaper, that does

not mean that we should necessarily eat more. But the root cause of obesity is overeating.

So what drives this overconsumption?

Slide 1 There are many factors that can drive eating. One of the most important is reward,

the idea that we find high-sugar, high-fat palatable foods like chocolate more appealing,

more rewarding and more pleasurable to eat. Compared to bland foods like grains and green

vegetables, we experience chocolate as more rewarding, so much so that we will eat it even

when we are not hungry.

Slide 2 There is no doubt that we are more motivated to consume these rewarding foods in

preference to other sorts of food. But is it possible that our natural, evolved preference for

energy-dense foods could tip into something more dangerous?

Could we become addicted to these foods? By addiction I mean uncontrolled eating, eating

that does not result in a pleasant sensation of satiety and fullness but in physical discomfort

or feelings of regret or shame.

The idea of food addiction has been around for at least the past ten years and seems now to

have entered the public consciousness.

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Slide 3 This shows a selection of stories from the online media that compare overeating with

addictions to heroin or tobacco. It is certainly clear that heroin addiction and an addiction to

smoking exist, and on the face of it, it might seem appealing to consider that an addiction to

food also exists. Not least because understanding such a phenomenon might lead to a better

understanding of how the brain controls food choice.

But addiction of any sort is a complex condition, so what evidence is there for addiction to

food? Long gone are the days where people who misused substances were considered to

have some sort of behavioural or moral defect. We now recognise that using substances like

alcohol or tobacco or other drugs can change the way the brain functions, and change it in

an undesirable way. However, unlike say, diabetes for example, where the insulin and

glucose in a patients blood can be measured to provide a diagnosis, addiction is much

harder to define. Instead of being able to measure changes in body processes empirically,

we must use psychological or psychiatric criteria to define addiction.

Slide 4 Such criteria already exist to diagnose addiction to drugs. For a diagnosis several but

not all of these criteria need to be fulfilled. One is tolerance needing more of the drug to

achieve the same effect. Others are the development of a withdrawal syndrome after

stopping use, taking more of the substance than one intends, unsuccessful attempts to stopusing the substance, or continued use despite unwanted consequences.

Is it possible that these criteria could be adapted to develop a way of defining food

addiction? Recently, that has been attempted by adoption of the Yale Food Addiction Scale.

This scale has been proposed to be a valid way of determining whether an individual is food

addicted.

Slide 5 The scale is a questionnaire that asks the responder to think about their eating

behaviour in the last year, with particular reference to palatable high-sugar or high-fat foods

like chocolate or fried foods. They are asked whether they frequently overeat even when

they are not hungry, whether they worry about eating certain foods, or trying not to eat

them, whether overeating or the fear of overeating has resulted in them missing work or

social activities, that sort of thing. By indicating how often they have such feelings or

experiences a score is generated which is used as the basis for a diagnosis of food addiction.

Use of the Yale scale is starting to become rather widespread

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Slide 6 and it has been suggested that patients defined as food addicted using this scale are

more susceptible to food cravings and binge eating. Furthermore, these patients are

suggested to be more impulsive and more emotionally reactive. And they may also show a

greater tendency to eat during periods of stress.

There is, rightly I think, a reluctance to characterise extreme forms of everyday activities as

psychiatric or medical problems. How would we decide who lies at the upper limit of normal

behaviour and who is at the lower limit of food addicted? As with most psychiatric diseases,

this would be decided case by case with the attendant problems of different diagnoses

between different psychiatrists and so on. And if food addiction does exist does it

necessarily lead to obesity? Is it possible that a food addict could maintain a normal body

weight? Similarly, it is surely not the case that all obese individuals are addicted to food.

Slide 7 At any rate, what might be the consequences of acceptance by the medical

community of food addiction as a real phenomenon? Might it lead to a reduction in personal

responsibility in certain groups? Would the overweight claim No! This is not my fault! Im

addicted to food, my brain made me do it!. Would there be a rush to medicalise the

problem?

Would drug companies try to develop treatments for food addiction? Perhaps by adaptingmedicines already used for, say, alcohol dependence? How would the food industry

respond? A new market could open up foods for the food-addicted. Would governments

feel compelled to act to control this new public health problem, to create legislation to

control our access to foods? Even if we could treat food addiction, what unintended

consequences might that have on other normal human behaviours?

Considering what we currently understand about the pathways in the brain that mediate the

sensations of reward and pleasure, it seems to be the case that the pleasure associated with

many behaviours, not just eating, but sex and caring for ones children for example, all

converge on the same brain pathways. If we were able to reverse food addiction by reducing

the reward and pleasure associated with food maybe there would be unintended

consequences. Perhaps we would also dull our responses to the other pleasures of life.

Surely an unwanted outcome.