Childhood Obesity in the UK: Is Fast Food a Factor? Peter Dolton (Royal Holloway College, University of London and Centre for Economic Performance, London School of Economics)

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Childhood Obesity in the UK Is Fast Food a
Factor?Peter Dolton(Royal Holloway College,
University of London and Centre for Economic
Performance, London School of Economics)
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MOTIVATION
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Source Brunello et al Economic Policy (2008)
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• Annual Reviews

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Motivation

• Obesity is 2nd biggest cause of death in the UK
  (after smoking).
• 23 of men obese and 24 of women 2008
• Wanless report obesity costs - 3.6 billion a
  year.2007
• Obesity rates have risen by 65 for boys and 51
  for girls in the last 10 years. up to 2005
• 10 of kids obese by the time of starting primary
  school (17 in deprived areas) 2008
• Fat kids make fat adults.

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KEY QUESTIONS
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Main Research Questions

• Can we explain what causes childhood obesity (and
  why it is rising)?

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Main Research Questions

• Can we explain what causes childhood obesity (and
  why it is rising)?
• Does Fast Food have a causal impact on childhood
  obesity (which can be identified)?

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Main Research Questions

• Can we explain what causes childhood obesity (and
  why it is rising)?
• Does Fast Food have a causal impact on childhood
  obesity (which can be identified)?
• Does Fast Food Outlet Proximity have a causal
  impact on Childhood Obesity?

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ANSWER

• The answer is NO!!!!! There is no causal link
  between fast food proximity and obesity
• Note this does not mean that I am saying FF if
  you eat enough of it does not make you fat.
• It merely says that having a FF outlet near does
  not cause you to be fat.

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How Do We Answer the Question?

• To answer this question properly we would need a
  controlled experiment with some children
  exposed randomly to FF and others not.
• We would also need to know exactly what else the
  children ate to control for variations in eating
  patterns and calorie intake.
• Such data does not exist.

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Currie, Della Vigna, Moretti and Pathania
AEJ(P),NBER 2009

• Taken together, the weight of the evidence is
  consistent with a causal effect of fast-food
  restaurants on obesity rates among 9th graders
• We find that among 9th grade children, a fast
  food restaurant within one tenth of a mile from a
  school is associated with at least a 5.2
  increase in obesity rates.

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WRONG!!

• US is full saturated with FF and so no control
  group.
• They only find their effects at .1 of a mile in
  the school playground!!!
• Hence I will look at the nearest thing we have to
  an experiment.

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UK Cohort Data

• 1946 NSHD Cohort
• On food rationing up to age of 8.
• 1958 NCSD Cohort
• Control cohort
• 1970 BCS Cohort
• Fast Food Cohort

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Fraction Obese by Cohort at Age 15/16.
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WHAT MY RESEARCH DOES

• Takes a cohort of children born in 1970 (BCS
  1970) and follows them through to adulthood.
• Merges all their data with information on WHERE
  and WHEN ALL fast food outlets opened in Britain.
• Estimates the effect of fast food outlet
  proximity on childrens BMI.

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BCS70 DATA
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BCS70 Follow-ups
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Fast Food Data

• Collected data on all the fast food outlets over
  1968-1986 and their year of opening and their
  exact location.
• Includes
• McDonalds
• Wimpy
• Burger King
• Kentucky Fried Chicken

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What counts as Fast Food??

• Use Counter service
• Kids can buy it served at source to eat
  immediately, at any time of the day, and take
  away.
• Fish and Chips was everywhere so is assume to
  be a constant background effect (as is changing
  supermarket food like microwave meals)
• Fish and Chips only available at frying times.

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When did they open?
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How can we measure Fast Food Treatment?

• Distance to nearest outlet.
• Number of outlets
• Currie et al (2009) use dummy if there is a FF
  outlet with .1 of a mile. (Also measure obesity
  as fraction in class x year who are obese.)
• I use Distance x Years of opening to give
  intensity of treatment.

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Key Explanatory Variables

• Psychological Problems Any evidence of any
  emotional or behavioural problem since 10 as
  reported by doctor.
• Physical Handicap Any evidence of significant
  illness, developmental problem, defect or
  handicap as reported by doctor.
• Exercise Participation in any sport 3 times a
  week or more self reported.
• High Calorie Diet Consumes any of
  hamburger/beef burger, pudding, butter,
  chocolate, sweets, ice cream, cake or buns,
  biscuits, chips, takeaway, white bread more than
  three times a week reported by mother.
• Eating Problems Parental reported eating or
  appetite problems.
• Screen Hours Total of TV time, DVD time and
  computer time in a day.
• Teen Eats Takeaway Teen eats Takeaway meal as
  reported by the mother.

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Summary of BCS70 Findings _at_ 16

• NO FAST FOOD EFFECT
• Think of average kid with BMI of 20 then 1 unit
  of BMI 5 extra body mass.
• Both
• Own BMI at age 10 (1.25 units of BMI _at_ 10 1 unit
  of BMI)
• Mothers BMI (10 units of Mothers BMI 1 unit of
  BMI)
• Screen Time (approx 10 hrs per day 1 unit BMI)
• For Boys only
• Psychological Problems (extra .8-1.6 units of
  BMI)
• Inner London (up to 3 units of BMI)
• Mother Works (2.5 unit of BMI)

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Extra Findings

• Number of Takeaways per week does not correlate
  with BMI.
• Fizzy drinks alone is significant for boys 5
  drinks a day 1 BMI
• Urban/Rural location is not significant.
• No Fast food effect at 26.

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MAIN Conclusions

• In the UK Fast Food Proximity does not have an
  impact on childhood BMI/Obesity.
• In so far as it is identifiable the effect of
  eating FF is not clear on BMI we just dont
  observe EXACTLY what an individual eats.
• Proximity of FF outlets does have an effect on FF
  consumption.

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Other Findings

• Main factors in BMI at 16 are own BMI at 10,
  Mothers BMI.
• Exercise has no impact on BMI.
• Fizzy drinks do impact on BMI.
• Screen Time does impact on BMI.
• For boys emotional /behavioural problems are a
  factor.
• Increased FF consumption reduces consumption of
  Vit C and fibre and increases consumption of
  crisps, fizzy drinks and fatty food.
• FF outlet location is not related to where fat
  people live.

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Tentative Implications

• Blaming Fast food outlets may be wrong.
• A huge fraction of overweight risk is from your
  genes and your family environment.
• Onus must be on mothers to control kids diet (and
  their own diet) when young.
• Fast food outlets dont have information to
  locate where fat people are but they do cite
  where poor people in work and ethnic minorities
  are.

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EXTRA SLIDES
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Outline of Talk

• Motivation
• Literature
• Identification and Causality?
• Measuring Childhood Obesity
• BCS Cohort Data and Fast Food Data Fast Food
  Treatment.
• BCS 1970 Results
• Conclusions and Policy Implications

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David Cameron 2008

• We talk about people being at risk of obesity
  instead of talking about people who eat too much
  and take too little exercise its as if obesity
  is a purely external event like a plague or bad
  weather

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Source Anderson et al NBER paper (2007)
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The Literature - Effect

• Chou et al (2004) (J of H Econ) state wide US
  data find an effect.
• Dunn (2008) (mimeo) IV of interstate exits
  10increase in FF density gives .33 of BMI
• Davis and Carpenter (2009) (Am J of Pub Health)
  Uses US data from CHKS over the 2002-2005 period.
• Currie et al (2009) (AEJ(P), NBER) Use US data
  from 1999-2007 for Californian kids.

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The Literature No effect

• Burdette et al (2004) (Preventive Med) 7,000 Ohio
  kids.
• Simmons et al (2005) (Int J of Obesity) find no
  relationship in Australia.
• Powell (2009) (J of H Econ) uses US data from
  NLSY data over teenagers from 1997-2003
• Anderson and Matsa (2009) (mimeo) Use adjacent
  highways as IV and find no effect.

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What this paper does that is new

• (To my knowledge) First study in the UK
• Set at a time when fast food outlets were growing
  exponentially.
• Use distance from home not school.
• Know all - not just the closest restaurants.
• Know the timing of the opening of the fast food
  restaurants - hence can work out a measure of
  duration intensity of fast food treatment'.
• Uses medically measured height and weight (not
  self reported)
• Other detailed data Mothers BMI, Screen time,
  mothers work etc.
• New identification clarity.

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Identification and Causality?
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Base ModelCurrie et al (2009), Chou et al
(2004), Burdette et al (2004), Powell (2009)

• BMI is a measure of obesity
• R is a measure of (EXOG) FF treatment
• X is observable controls
• X unobservables

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How are R BMI measured?

• Chou et al (2004), Powell (2009) measure R by
  number of restaurants at the state level.
• Currie et al (2009) measure R as the proximity of
  the FF outlets from school and BMI as the of
  kids in a class who are fit.

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IV ModelAnderson and Mata (2009) Dunn(2008)

• Assumption here is that R is endogenous and we
  need to find IVs, Z for it. Anderson Matsa use
  interstate highways and Dunn uses exits.

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Full Model

• Here we make a distinction between consumption
  of FF and Proximity of FF outlets.
• T is a measure of Take-away consumption. May
  be endog in which case could use FF outlet
  proximity, R as an IV.

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Measuring Childhood Obesity
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How do we measure BMI?

• BMI Quetelet Index

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BMI Classification for Adults
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BMI for kids

• Use the LMS tables generated by Pan and Cole for
  the MRC
• Gives Obese BMIs as

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Fraction Obese by Cohort at Age 15/16.
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Local Examples

• Norwich
• 1978 Wimpy opened (Ipswich had one in 1977!!!)
• 1981 McDonalds opened
• 8 Fast food outlets by 1981
• Lancaster
• 1977 Wimpy opened
• 1980 McDonalds opened
• 4 Fast food outlets by 1980

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Duration Intensity Treatment of Fast Food

• Where Y is years since outlet k opened, and d is
  distance from individual i. This measures DITFF
  for less than 5 miles.

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8 year _at_ 1 mile 2(1 year _at_ 4 miles)
Example Duration Intensity of Fast Food
Treatment Additive Measure
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Reasons why it is interesting to look at location
of kids home and fast food outlets

• 1. At least 50 of the days in a year kids dont
  go to school if we count weekends and holidays
  and absence. They are only there for 6 hours and
  all but 1 are in lessons. So only around 2-3 of
  time can get FF at school.
• 2. Only 2.2 of primary kids age 10 in 1980 ate
  their midday meal outside school but not in the
  family home.
• 3. Only 15 of secondary kids age 16 in 1986 ate
  their midday meal outside school but not in the
  family home.

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Full Model

• Here we make a distinction between consumption
  of FF and Proximity of FF outlets.
• T is a measure of Take-away consumption. May
  be endog in which case could use FF outlet
  proximity, R as an IV.

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Eqn (3.2) First Stage IV
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Identification Issue

• Does living near Fast Food outlet cause you to
  be fat?
• OR
• Do Fast Food outlets cite near people who are fat
  and/or do people who have a propensity to be fat
  choose to live near FF outlets?

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Full Model

• Here we make a distinction between consumption
  of FF and Proximity of FF outlets.
• T is a measure of Take-away consumption. May
  be endog in which case could use FF outlet
  proximity, R as an IV.

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Trying to establish Causality?!

• Took all the Youth Cohort Surveys 1-7 over the
  whole period of the 1983-1992 to characteristics
  of the LEAs

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Source from Cummins et al (2005) Int J of
Behavioral Nutrition and Physical Activity.
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Possible explanations of why I dont find anything
of a fast food effect

• 1. Using home rather than school.
• 2. Just too early - the data which finds an
  effect is for the US and in the 2000s.
• Powell uses US data from NLSY data over
  teenagers from 1997-2003
• Davis (2009) Uses US data from CHKS over the
  2002-2005 period.
• Currie et al (2009) Use US data from 1999-2007
  for Californian kids.
• 3. Its just a US effect - At present there is no
  evidence from any other country that there is an
  effect.
• Simmons et al (2005) find no relationship in
  Australia.
• 4. Methodology or claimed causality on other
  papers is dubious. How can we be sure that fast
  food restaurants do not locate where fat people
  (or people who have a propensity to consume more
  highly) live. i.e. fast food outlets locate
  where there are already fat people rather than
  the location of the fast food outlet causes
  people to become fat. All the papers purporting
  to find this effect do not satisfactorily tackle
  this question.
• 5. My measure of intensity of treatment is
  wrong.
• There simply is no causal effect for proximity of
  fast to children's whereabouts.
• Takeaways do not induce BMI gain as kids
  substitute calories when they take fast food we
  do not have good enough data to tell us about how
  FF substitutes for other food.

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Issues in Obesity Literature.

• Does maternal working play a role in childhood
  obesity? (Anderson et al 19 )
• Is SES related to obesity? (Baum and Ruhm )
• Does mothers BMI impact on childs obseity
  (Parsons et al )
• Height is related to Earnings. (Case and Paxson)
• BMI is negatively related to earnings for women.
  Blanchflower and Sargent (1980) Morris
• Childhood obesity is not linked to adult outcomes
  (Viner and Cole)
• Relation between screen viewing and obesity.

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Other Geographical Studies

• Cummins MacIntyre (2005) (Int J of Epidemiolgy)
• Cummins et al (2005) Int J of Behavioral
  Nutrition and Physical Activity.
• Morland Evenson (2009) (Health and Place)

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The Data

• 1946 NSHD Cohort
• On food rationing since up to age of 8.
• 1958 NCSD Cohort
• Control cohort
• 1970 BCS Cohort
• Fast Food Cohort

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NHSD Follow-ups

• Socially structured sample of 5362 singletons
  born in one week in March 1946.
• Followed at Birth
• 2,4 response 95
• 6,7,8,9,10,11,13,15 response 85

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NCDS Follow-ups
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Additional features of the data

• Have a 'rationed' and 'control' generation to
  examine the context of weight gain of teenagers
  over the period 1962-1986.
• Have repeated measure of BMI - i.e. longitudinal
  data and can model changes and identify changes
  in intensity of fast food treatment on weight
  gain.
• Know an extremely rich set of covariates
  including mothers and father own BMI - no other
  studies have access to such controlling data to
  provide a context of genetic and family
  environment factors.

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Main Results of Cross Cohort Comparison

• At 10/11 mother works increases BMI
• At 10/11 social class effects
• At 10/11 Birth weight effects.
• At 15/16 still social class effects
• At 15/16 no mother works effect
• At 15/16 BMI _at_ 10/11 is main driver.