Why the Recent Obesity Epidemic?
Many competing hypotheses
Childhood Obesity
Session II
Roland Sturm, Ph.D.
Senior Economist
RAND
¾
Television/Video
¾
Too much homework
¾
Less exercise
¾
More fast food
¾ Urban Sprawl/Car Culture
Identifying major social trends can
suggest promising interventions
Actual changes at times surprising
A5087-2 01/04
What has changed in children’s lives?
We will look at trends in
1.
Time Use
2.
Media Consumption
3.
Studying at Home
4.
Transportation Patterns
5.
Physical Education
6.
Nutrition
This session is not about health care!
Obesity has major effects on health
care use among adults
But the most effective solutions are in
prevention, not treatment (at this
point)
Health plans and health care settings
have little leverage
Environmental influences on health
A5087-3 01/04
A5087-4 01/04
While Adults Have More Free Time ….
• Best methodology: time diaries
• Census Bureau started collecting time diary data
in 2003
• For adults, 1965-1985 data from Robinson and
Godbey; my calculations from 1999 survey
• For children, only two surveys available: 1981
and 1997 (Hofferth and Sandberg)
• Time allocation important for physical activity,
less for nutrition
Occupation
Travel
Hom e Total
Leisure Total
Average Minutes Per Day
1. Time Use
350
300
250
200
150
100
50
0
1965
1975
1985
1999
Source: Robinson and Godbey, 1999; my calculation using FISCT 1999
A5087-5 01/04
A5087-6 01/04
1
…. Free Time for Children Declined from 1981
to 1997 (in mins/week)
442
For adults 18-64, free time increased by 6
hours per week from 1965 to 1995
– increase for both men and women
– in or out of labor force
419
408
Trends in Time Use
337
For children 3-12, free time decreased by 7
hours per week from 1981 to 1997
age 3-5
age 6-8
age 9-12
all ages
Source: calculations based on data from Hofferth and Sandberg (2001)
A5087-7 01/04
Changes in Weekly Minutes Spent on
Activities from 1981 to 1997, Age 3-12
A5087-8 01/04
Changes in Weekly Minutes Spent on
Activities from 1981 to 1997, Age 3-5
Figure
400 2: Changes in Weekly Minutes Spent on Activities from 1981 to 1997, Age
366
3-12
600
(246)
Source: calculation based on data from Hofferth and Sandberg (2001b)
-400
(94)
(509)
-600
-400
Source: calculations based on data from Hofferth and Sandberg (2001)
Playing
(82)
Other passive,
Conversations,
Church,Visiting,
Leisure
Television
Shopping
-200
Personal care
Playing
Television
(162)
69
134
0
Sports / Outdoors
-300
(138)
181
200
School, Daycare,
Studying, Reading,
Art Activity
-200
61
405
400
Minutes per week
-100
73
Shopping
0
Personal care
100
Sports / Outdoors
107
School, Daycare,
Studying, Reading, Art
Activity
Minutes per week
200
Other passive,
Conversations,
Church, Visiting,
Leisure
300
A5087-9 01/04
A5087-10 01/04
Source: calculation based on data from Hofferth and Sandberg (2001b)
Changes in Weekly Minutes Spent on
Activities from 1981 to 1997, Age 6-8
Changes in Weekly Minutes Spent on
Activities from 1981 to 1997, Age 9-12
600
-400
(181)
Source: calculation based on data from Hofferth and Sandberg (2001b)
(228)
- 300
- 400
Shopping
- 200
Playing
- 100
Television
90
27
Personal care
(135)
92
0
Sports / Outdoors
-300
(46)
92
100
School, Daycare,
Studying, Reading,
Art Activity
-200
Shopping
-100
Personal care
0
200
Minutes per week
100
99
369
300
Playing
100
400
Television
200
School, Daycare,
Studying, Reading,
Art Activity
Minutes per week
300
Sports / Outdoors
400
Other passive,
Conversations, Church,
Visiting, Leisure
500
485
Other passive,
Conversations,
Church, Visiting, Leisure
500
(163)
(385)
- 500
A5087-11 01/04
Source: calculation based on data from Hofferth and Sandberg (2001b)
A5087-12 01/04
2
What has changed in children’s lives?
2. Media Consumption
We will look at trends in
• Common hypotheses:
1.
Time Use
2.
Media Consumption
3.
Studying at Home
4.
Transportation Patterns
5.
Physical Education
6.
Nutrition
–Children watch more TV
–Children spend too much time
playing video games, on
computer
• No trend data available except TV
• But KFF point-in-time media use
project
A5087-13 01/04
Continuing Decline in TV Watching Among
Teenagers: 1991-2001
40%
35%
30%
1 Hour or Less
2 - 3 Hours
20%
4 or More Hours
15%
10%
5%
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
0%
Analysis by Child Trends based on data from Monitoring the Future, 1990-2001, A5087-15
available at http://www.childtrendsdatabank.org/indicators/55WatchingTV.cfm
Media Use Among 8-18 Year Olds
(hours per day)
Medium
Total
Television
TapedTV
Videotapes
Movies
Videogames
PrintMedia
Radio
CDsandTapes
Computer
45%
25%
A5087-14 01/04
WhiteBlackHispanic
7:16 9:52 9:02
2:47 4:41 3:50
0:12 0:27 0:18
0:28 0:32 0:34
0:13 0:29 0:35
0:23 0:35 0:35
0:43 1:16 0:35
0:49 0:45 0:56
1:09 1:03 1:08
0:31 0:31 0:29
01/04
Summary: Media Consumption
A5087-16 01/04
Source: Kaiser Family Foundation, 1999, kds & media @ the new millennium.
What has changed in children’s lives?
We will look at trends in
• Noticeable decline in television
watching
• Computer/video games relatively small
share of media budget
–Total comparable to TV decline
• Either little change in screen time or
decline
A5087-17 01/04
1.
Time Use
2.
Media Consumption
3.
Studying at Home
4.
Transportation Patterns
5.
Physical Education
6.
Nutrition
A5087-18 01/04
3
Proportion of adolescents doing 1 hour or
more of homework, 1978-1999
3. Studying at Home
• Claims that homework “overburdens
100
children and limits learning” with lack of
physical activity and weight gain being
major secondary consequences (Kralovec
& Buell, 2000).
• There is indeed a large increase in
children’s “occupational” time
– includes studying at home, day care
and after school programs
• Could changes in homework account for
this?
90
80
70
60
40
30
20
10
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
Source: Gill and Schlossman (2003)
Homework trends for 9-year-olds, 1984-1999
A5087-20 01/04
Summary: Studying at Home
• Studying at home not cause for children’s
90
increased “occupational” time
80
• Increased homework loads cannot play any
70
% of students
1980
1978
0
A5087-19 01/04
100
age 13
age 17
50
hw assigned
yesterday
60
50
one hour or more
40
30
20
10
2000
1998
1996
1994
1992
1990
1988
1986
1984
0
Source: Gill and Schlossman (2003)
role in weight gain/declining physical
activity
• Refutes prominent hypotheses in education
literature
• Main reason for increased “occupational”
time: after- school and daycare
A5087-21 01/04
A5087-22 01/04
Walking to School as Percent of
School Trips (Children 5-15)
What has changed in children’s lives?
We will look at trends in
1.
Time Use
2.
Media Consumption
3.
Studying at Home
4.
Transportation Patterns
5.
Physical Education
6.
Nutrition
25
20.2
20
16.6
15
12.5
10
5
0
1977
A5087-23 01/04
1990
2001
Source: NPTS 1977, 1990 and NHTS 2001 for children 5-15
A5087-24 01/04
4
Total Number of Daily Trips
4
Average Active Travel Time in
Minutes (Children 5-15)
3.5
3.5
8
3.1
7
6
3
2.2
Minutes
2.5
2
1.5
5
2
0.5
1
0
1977
1990
3.9
4
3
1
0
6.3
2.7
1977
2001
Source: NPTS 1977, 1990 and NHTS 2001 for children 5-15
2.1
0.6
0.3
1990
Walking
Source: NPTS 1977, 1990 and NHTS 2001 for children 5-15
A5087-25 01/04
Summary: Transportation
2001
Bicycling
A5087-26 01/04
What has changed in children’s lives?
• Decline in walking to school opportunity for
We will look at trends in
interventions to increase physical activity
• Not clear that changes in transportation
reduced physical activity
• Possibly even small increase in active travel
because of increased number of trips
• But total amount of active travel remains
negligible: not even 10 minutes/day
1.
Time Use
2.
Media Consumption
3.
Studying at Home
4.
Transportation Patterns
5.
Physical Education
6.
Nutrition
A5087-27 01/04
A5087-28 01/04
Percentage of students who attended
PE class one or more days during
an average school week
• School and afterschool/daycare
important as children spent more time
in those settings
• Widespread belief that PE is declining
• Only trend data for high school
100
80
Percent
Physical Activity at School
60
59.6
48.9
52.1
1991
1993
56.1
51.7
48.8
40
20
0
A5087-29 01/04
1995
Source: CDC, YRBS, various years
1997
1999
2001
A5087-30 01/04
5
Percent of students who exercised or
participated in physical activities for at least
20 minutes that made them sweat and breathe
hard on three or more of the past seven days
Percent of students attending daily PE classes
100
90
80
70
Percent
80
65.8
63.7
63.8
64.7
64.6
60
P e rc en t
100
50
41.6
40
60
30
40
20
20
10
34.3
25.4
27.4
29.1
32.2
1995
1997
1999
2001
0
0
1993
1995
1997
1999
1991
2001
Source: CDC, YRBS, various years
Source: CDC, YRBS, various years
A5087-31 01/04
Physical Activity At School
1993
What has changed in children’s lives?
• For adolescents, not clear that PE declined
• Overall PA for adolescents seems constant
• No trend data on younger children, although
We will look at trends in
time in organized sports increased
• Missing: What is going on in
afterschool/daycare?
• Important policy lever as PE as early as
elementary school can substantially reduce
further weight gain among heaviest girls
1.
Time Use
2.
Media Consumption
3.
Studying at Home
4.
Transportation Patterns
5.
Physical Education
6.
Nutrition
A5087-33 01/04
A5087-34 01/04
While Leisure Industries Are Growing Fast,
Food Industries Decline in Importance …
… But Supply More Calories
U.S. Food Supply, Energy per capita per day
4,000
15.0
3,800
10.0
3,600
kcal
Percent
Food Expenditure as Share of
Disposable Personal Income
5.0
0.0
3,400
3,200
19
73
19
76
19
79
19
82
19
85
19
88
19
91
19
94
19
97
20
00
Food At Home
A5087-32 01/04
Food Away From Home
Source: USDA, Economic Research Service
3,000
Total
A5087-35 01/04
Source: USDA, Economic Research Service
A5087-36 01/04
6
Daily Fat and Carbohydrate Intake for
Boys and Girls Ages 6-11
US Food Supply for Macronutrients
300
500
250
400
77-78
200
300
grams
Grams per capita per day
600
200
89-91
150
94-96,98
100
100
0
Carbohydrates
Protein
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
1970
50
0
Fat
Total Fat
Carbohydrates
Fat
Boys
Source: USDA, Economic Research Service
A5087-37 01/04
Source: Enns et al. (2002) based on Continuing Survey of Food Intakes by Individuals (CSFII) 199496, 1998; CSFII 1989-91; Nationwide Food Consumption Survey 1977-78.
Price Indices
A5087-38 01/04
Total Caloric Sweeteners
300.0
160.0
200.0
Consumer
Price
Index
150.0
Sugars
and
Sweets
Soft Drinks
100.0
150.0
Pounds per capita
Fresh
Fruits and
Vegetables
250.0
1982-1984=100
Carbohydrates
Girls
140.0
130.0
120.0
110.0
100.0
19
66
19
69
19
72
19
75
19
78
19
81
19
84
19
87
19
90
19
93
19
96
19
99
20
02
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
50.0
Source: USDA, Economic Research Service
A5087-39 01/04
Interventions? Politically touchy…
Source: USDA Economic Research Service
A5087-40 01/04
Hardball Responses From Industry
See fight about 2003 WHO report, which says:
• For example, an excerpt from a letter from the Sugar
Association
• “Overall, the evidence implicating a high intake of
• The senators referred to are John Breaux and Larry Craig
sugars-sweetened drinks in promoting weight gain was
considered moderately strong.”
• “Part of the consistent, strong relationships between
television viewing and obesity in children may relate to
the food advertising to which they are exposed.”
• “Fastfood restaurants, and foods and beverages that
are usually classified under the ‘‘eat least’’ category in
dietary guidelines are among the most heavily
marketed products, especially on television.”
A5087-41 01/04
A5087-42 01/04
7
Summary: Nutrition
Conclusion
¾
Time spent eating as a primary activity has
declined, suggesting a shift towards snacking
or eating as a secondary activity.
¾
Statistically significant increase in carbohydrate
intake
¾
Price and income data suggest possible
economic reasons
¾
Price index for fresh fruit and vegetables far
exceeded general inflation, whereas real price
for sugars, sweets, soft drinks fell.
¾ Biggest
changes are decline in children’s
free time and nutrition
¾ No
major trends in PA related to PE,
active travel (except walk to school),
home studying, media
¾ Increased
A5087-43 01/04
time in school, daycare, and
after- school programs offer
opportunities for intervention
¾ Both for PA and nutrition
A5087-44 01/04
8