Eating disorder

Are consumers ‘rational’ is the sense of trying to maximise consumer surplus? In some circumstances the answer is yes. When we go shopping we do generally try to get best value for money, where value is defined in terms of utility. With limited incomes, we don’t want to waste money. If we were offered two baskets of goods costing the same amount, we would generally choose basket A if its contents gave us more utility than basket B.

So why do we frequently buy things that are bad for us? Take the case of food. Why do we consume junk food if we know fresh produce is better for us? To answer this we need to look a little closer at the concept of utility and what motivates us when we consumer things. The following article does just that. It reports on writings of Michael Pollan. Pollan looks at our motivation when choosing what and how much to eat. For much of the time our choices are governed by our subconscious and by habit.

“Millions of humans, while believing they govern their actions with conscious intelligence, clean every morsel from their dinner plates, mainly because their parents told them to. And we do this even if we don’t particularly like the food on the plate and even if we know we should be eating less of it. Unthinkingly, we follow a habit we would condemn if we looked at it clearly.”

You mar what you eat and the politics of Michael Pollan National Post (Canada), Robert Fulford (18/1/10)


  1. What is meant by ‘rational behaviour’? Is it reasonable to assume that people are rational in most circumstances?
  2. Is eating junk food consistent with the attempt to maximise consumer surplus?
  3. How relevant is the principle of diminishing marginal utility in explaining the amount of junk food we eat?
  4. To what extent are the problems that Pollan identifies examples of (a) imperfect information; (b) irrationality?
  5. What does people’s eating behaviour reveal about their preferences for the present over the future and hence their personal discount rate?
  6. What are the policy implications of Pollan’s analysis for governments trying to get people to eat more healthily?