1、IntroCalorie deprivation(in moderation)can make you healthierCuba after the collapse of the USSRThe starvation experiment at the University of Minnesota during WWIIObesity is a growing problem in the US and worldwideWhy?What is causing this epidemic?Is it a public health crisis?What government respo
2、nses are appropriate?Ch 22|ObesityTHE WIDESPREAD RISE IN OBESITYWhen is a person obese?Q:Is a man who weighs 180 pounds obese?A:That depends whether the person is five feet tall or seven.Clearly,some accounting must be made for height in defining obesity.The canonical way to do this is calculate the
3、 body mass index or BMI:A person is considered clinically obese if his or her BMI is 30 or greater.Obesity rates are risingBody weight in the U.S.has been rising in fits and starts for at least the past 150 years.The proportion of adult Americans who are obese has more than doubled between 1977 and
4、2006.Body weight has been increasing for decades in every developed country in the world.The heaviest countries are all in the Anglosphere.Ch 22|ObesityWHAT EXPLAINS INCREASING OBESITY?What explains increasing obesity?Theory 1:GeneticsEvidence suggests that genetics plays a key role in determining b
5、ody weight for both children and adults.While genetics may predispose some to being heavy,they cannot be the reason for the rise in body weight.What explains increasing obesity?Theory 2:The food industryOne popular theory for explaining obesity levels is that fast food restaurants and agricultural c
6、orporations push unhealthy,fattening foods and large serving sizes on an unwary populace.There is evidence that living close to fast food restaurants increases bodyweight,especially among children.But even if the popularity of fast food restaurants has contributed to rising obesity since World War I
7、I,bodyweight has been increasing since at least the mid 19th-century.What explains increasing obesity?Theory 3:Food price trendsSince WWII,improvements in the technology of agriculture have made food production substantially cheaper and driven down its price.The law of demand says that a decline in
8、the price of a normal good will be met with an increase in the quantity consumed of that goodand people have responded to these price decreases just as expected.While some have pointed to rising portion sizes at meals as a cause of rising body weight,those rising portions are themselves a consequenc
9、e of falling food prices.What explains increasing obesity?Theory 4:Changing lifestyles Sedentary Jobs:The labor economy in the developed world,which previously consisted largely of agricultural jobs,has become dominated by service and manufacturing jobs,which require less physical activity.Heating a
10、nd AC:Bodies expend energy to cope with hot and cold temperatures,so air conditioning and central heating may be contributing to fat staying on bodies rather than being burned off.Automobile use:The automobile is credited with dramatically reducing average daily walking exercise in developed countri
11、es.What explains increasing obesity?Theory 5:Labor force participationIn the Western world,the increase in labor force participation by women,and the simultaneous decline in the average time spent preparing meals at home,has contributed to rising body weight.This same force has contributed to the ri
12、sing share of food dollars spent on restaurant food,which is often more calorically dense and fattening than food prepared at home.Technological changes that make housework less onerous,such as the invention and dissemination of dishwashers and microwaves,have also decreased the relative price of la
13、bor force participation.Obesity is a side effect of good thingsLower food pricesLabor-saving technological innovationsModern conveniences(air conditioning,cars)Economic opportunities for womenCh 22|ObesityTHE COSTS OF OBESITYThe costs of obesityHigher health care costs:Annual medical expenditures in
14、 the U.S.are 36%higher for obese people than thinner people.Reduced life expectancy:A 40-year-old white male with BMI 35 has a life expectancy three years shorter than one with BMI 24.Increased risk of chronic diseases such as heart disease,diabetes,and hypertension.Reduced physical mobility and fun
15、ctionLower wagesSocial stigmaCrucial question:are these public or private costs?Ch 22|ObesityIS OBESITY A PUBLIC HEALTH CRISIS?Is obesity a public health crisis?For an economist,it is the distinction between public and private costs that determines whether obesity is a public health crisis rather th
16、an a significant but private problem.Is obesity a public health crisis?Under this welfare economics rubric,an outbreak of tuberculosis is a public health emergency,but a rise in the prevalence of back pain is not.In the case of tuberculosis,drastic public action,like quarantines,may be justified.Wit
17、h back pain,no government action is justified because,unlike a tubercular patient in a crowded room,a person with back pain inflicts no costs on others.If painkillers or surgery are worthwhile,the person with back pain will pay for it.How might one persons obesity be costly to someone else?Only one
18、obvious pathway:pooled health insurance.Pooled health insuranceExample:Imagine that Homer,Carl,Lenny are in a pooled workplace health insurance plan at the Springfield nuclear power plant.Homer pays the same amount to qualify for health insurance coverage as his colleagues Carl and Lenny.Homer is da
19、ngerously obese and likely to generate substantial medical costs in the coming year,whereas Carl and Lenny eat organic greens every day and have not needed medical care in decades.Suppose that each additional jelly donut Homer eats raises the total medical bill for the entire nuclear plant by$1.Beca
20、use Homer is one of hundreds of employees,his own health insurance premium only rises by a fraction of a cent with each donut he eats.Pooled health insuranceThus,by pooling together in the same insurance plan,Carl,Lenny and everyone else in the pool subsidizes Homers costly jelly donut habit.In this
21、 way,pooled insurance creates an artificial externality where none existed naturally.While this cross-subsidization induced by pooled insurance seems like a problem from a social planners point of view it is not certain that social welfare actually declines as a result.If Homer gains a dollar from t
22、he insurance cross-subsidization while the other employees lose exactly a dollar in total,then health insurance induces a transfer but does not create any social loss.Moral hazard and health insurance For Carl,Lenny,and Homer alike,pooled health insurance reduces the price of unhealthy eating.Perhap
23、s Carl responds to pooling by joining Homer for jelly donuts,while Lenny skips his yoga exercises.This is a classic case of moral hazard:distortions in price induce changes in behavior that lead to a loss in social welfare.If this assumption holds,pool members eat too poorly,exercise too little,and
24、weigh too much relative to the social optimum.The presence of moral hazard in pooled health insurance implies a true public health crisis.Moral hazard and health insurance There is one important hitch to this reasoning that bears on whether the obesity epidemic is a public health crisis:Up to now,we
25、 have been discussing body weight choices as if they are firmly under our own control.But as anyone who has tried a diet and failed can attest,there are many influences on diet and exercise choices that most people can do little about.Example:Imagine Homers elasticity of demand for donuts with respe
26、ct to pooled insurance is zero.If so,pooled insurance does not change Homers behavior,and his gluttony causes no social loss because there is no moral hazard.The social loss caused by moral hazardRecall:if the demand for fattening foods is completely price-inelastic,social loss is zero from pooled h
27、ealth insurance.So the relevant question is:does health insurance make you fat?Does health insurance make you fat?According to the RAND HIE results above,more generous health insurance does not make people fat.But does moving from no insurance to some insurance makes enrollees fat?The evidence confl
28、icts on this point.Ch 22|ObesityOBESITY CONTAGION IN SOCIAL NETWORKSIs obesity contagious?Some researchers are concerned that obesity can“spread”not through physical contact like tuberculosis but through links in a social network.If obesity spreads this way,it would qualify as a public health crisis
29、 after all(even though we think pooled health insurance does not create social loss).Is obesity contagious?Researchers using data from a massive study of the residents of a Massachusetts town tested whether social networks spread obesityand they found evidence for obesity contagion.They found that s
30、ubjects are more likely to become obese if the people that they are tied to socially(friends,relatives,coworkers)became obese in a previous period.Further,obesity risk increases most dramatically when one person becomes obese in a mutually-perceived friendship.Is obesity contagious?As with most obse
31、rvational studies,questions of causality are not definitively answered here.Example:Perhaps if a pair of siblings become sick in quick succession,it is a sign of changing dietary habits or economic conditions.Or perhaps people choose friends on the basis of mutual interests that are fattening.One na
32、tural experiment conducted at the U.S.Air Force Academy provides useful insights:If a cadet was assigned to a dorm with poorly-conditioned dormmates,his performance on a Physical Education Assessment test tended to suffer accordingly.This study suggests that associating socially with less fit peers
33、does tend to degrade ones own fitness.Ch 22|ObesityOTHER JUSTIFICATIONS FOR PUBLIC HEALTH INTERVENTIONJustifications for public health interventionSo far,we have argued that a government intervention against obesity is not justified unless obesity causes a social loss through externalities.This is t
34、he welfarist point of view,because welfare economics assumes that individual choices should be respected by the government as long as they do not harm othersIf we relax that assumption,there may be additional justification for government action.Justifications for public health interventionInadequate
35、 nutritional information There is evidence that consumers are woefully unaware of the nutritional content of much of the food they eat.This lack of knowledge has been proposed as a justification for public intervention,such as nutrition facts labels and calorie posting requirements at restaurants.Ho
36、wever,the effectiveness of such measures has been questioned,as many consumers do not respond to this information.And even with perfect nutrition information,consumers may have trouble translating their food choices into health outcomes.Justifications for public health interventionChildhood obesity
37、Obesity during childhood is associated not only with obesity during adulthood but also with elevated rates of heart disease later in life and a shorter life span.Welfare economics starts from the premise that people know what is best for them,and that their actions reveal their true preferences.But
38、this assumption is less likely to hold when it comes to children,who may be uninformed about health risks,ill-equipped to think long-term about health decisions,and especially vulnerable to advertising for unhealthy foods.Justifications for public health interventionImpatience and addictionAnother c
39、ritique of the welfare economics argument posits that even adults do things that are bad for them.What if people gorge on cookies but regret it later?What if people become addicted to french fries and cannot stop even if they do not want to gain weight?These kinds of scenarios are the focus of an em
40、erging field called behavioral economics.A ban on unhealthy midnight snacks would certainly reduce obesityit may even be supported by the very people whose midnight snacks would be outlawed.But this kind of muscular government intervention raises profound questions about liberty and the fundamental
41、assumptions of welfare economics.ConclusionThe rapid rise of obesity and associated chronic diseases worldwide has inspired policy responses in many countries.New York City voted to ban the trans-fat in restaurants in 2006.Japan started charging higher premiums for citizens with waistlines above a m
42、aximum threshold in 2008.Denmark instituted a tax on all products with saturated fat in 2011.If there is no moral hazard,then these laws do not affect total social welfare,but they do introduce a regressive tax,since obese people tend to be poorer than thinner people.ConclusionThus,any government intervention should be scrutinized for unintended and harmful side-effects.Example:taxing fast food may rein in obesity,but would likely hurt the poor who rely on these sources of cheap food for important nutrients.
