Transcript Document

Epidemic obesity: where did it
come from, what does it mean and
where do we go from here?
Science and Society in the Tropics
Public Lecture May 21 2014 Cairns
Robyn McDermott
Centre for Chronic Disease Prevention
Australian Institute of Tropical Health & Medicine
Epidemics appear, and often disappear without
traces, when a new culture period has started;
thus with leprosy, and the English sweat. The
history of epidemics is therefore the history of
disturbances in human culture
Virchow, 1870
Tonight….
• The health transitions which have taken place in
humans in the past million or so years,
• The various theories behind the global obesity
and diabetes pandemic seen in the last 30 years,
• Ethnic variation in susceptibility to “diabesity”,
and what we can infer from that
• Finally, what does all this mean for health
services, the environment and the economy, and
what can be done.
Reasons to be optimistic
Perhaps the single greatest achievement of the
modern world has been a reduction in death
rates nearly everywhere and probably a very
substantial increase in the proportion of the
world’s inhabitants who feel really well most
of the time.
John Caldwell, 1989
DALYs, by broad cause group 1990 - 2020
in Developing Countries (baseline scenario)
%
50
1990
2020
25
DALY = Disability
adjusted life-year
Communicable diseases,
maternal and perinatal
conditions and nutritional
deficiencies
Injuries
Noncommunicable
conditions
Source: WHO, Evidence, Information and Policy, 2000
Diabesity in the USA
Obesity spread via social networks:
The Framingham offspring study
Source: Christakis, NEJM 2007
Prevalence of diabetes, Indigenous NQ (WPHC)
and Australia (AusDiab),
1999-2000
60
50
40
Non-Indigenous
Aboriginal
Torres Strait Islander
30
20
10
0
15-24 25-34 35-44 45-54 55-64
Source: McDermott et al, AHR 2003
65+
Generational transmission of diabesity
• Low birth weight, combined with weight gain
in adulthood, increases risk of CVD, diabetes,
some cancers
• Maternal obesity amplifies the risk of diabetes
in pregnancy, birth defects, childhood obesity
and type 2 diabetes
• Maternal obesity increases early death (before
age 60) by 35% in the offspring (BMJ 2013)
Mean women’s waist change over 5 years
(cm), 1999-2005 FNQ
Source: McDermott et al, PHN 2009
Dementia = “type 3 diabetes”
Risk of incident dementia by baseline glucose (no diabetes)
Source: Crane et al NEJM 2013 369:6 (pp540-8)
Various theories 1: GENES
Observations on ethnic differences in
susceptibility and genetic adaptation in
populations in a changing environment
• “Thrifty gene”
• “Drifty gene”
• “Out of Africa”: Migration and metabolic
adaptation to climate stressors
Human migrations and metabolic adaptation to different environmental
stressors: a new theory for ethnic obesity variation
Source: Sellayah D, et al “On the evolutionary origins of obesity: a new hypothesis. Endocrinology 2014:doi:
10.1210en.2013-2113
Aboriginal adults (Central Australia)
1930s
Torres Strait Islanders, 1930’s-40’s
Various theories 2: FOOD
Global pandemic diabesity since 1980 and
the hunt for culprit foods
New foods: cheap calories and processing
•
•
•
•
Fats
Fructose
Portion size drift
Availability, affordability and the social
gradient
Coronary mortality (deaths per 100,000) as a function
of saturated fat intake
Source: Kromhout et al Seven Countries Study, 1995 Prev Med
1400
1200
1000
800
600
400
200
0
0
5
10
15
20
25
Sugar consumption and obesity prevalence in
the USA, 1700-2000
80
70
60
50
Sugar consumption (kg/p)
40
Obesity prevalence (%)
30
20
10
0
1700 1750 1800 1850 1900 1950 2000
Source: Johnson et al, 2007. Potential role of sugar (fructose) in the epidemic of hypertension, obesity and the metabolic syndrome,
diabetes, kidney disease and cardiovascular disease. Am J Clin Nutrition
Dietary fructose in non-alcoholic fatty liver disease
Hepatology
Volume 57, Issue 6, pages 2525-2531, 1 MAY 2013 DOI: 10.1002/hep.26299
http://onlinelibrary.wiley.com/doi/10.1002/hep.26299/full#fig1
40
Energy cost and food prices
Beverages
oil
Cereals
30
Fats & oils
Fruit
Meat & meat products
margarine
Milk & milk products
Sugar & confectionary
Vegetables
20
crisps
10
sugar
flour
biscuit
cake
milk grain/starch
confectionary
dried Veg
dried Fruit
pies
chicken
hot chips processed
meat
bread
egg
beef
fruits
0
soft drink
Frozen Veg
vegetables
-2
0
2
4
Energy cost ($/MJ)
$0.14/MJ
$2.72/MJ
$7.40/MJ
$54.60/MJ
Source: Brimblecombe and O’Dea, MJA, May 18, 2009
Various theories 3: SITTING and not sleeping
Immobility (screen and car time) and sleep deprivation
Creeping Sleep Loss
Under sleep:
• Australians sleep 7.25 ± 1.48 h/night during the
week and 7.53 ± 2.01 h/night on weekends
• 18.4% working age group sleep <6.5 h/night
• Chronic sleepiness in 11.7% (Bartlett 2007)
Longer workday:
• Since 1969, Americans have added 158
hours/year to the workday (USA census data)
Longer commute:
• Work time and travel time the primary
activities reciprocally related to sleep time among
Americans (ATUS, Basner 2007)
Chronic short sleep has
consequences for
health
New York Times, 10 / 99
Sleep, Obesity and T2 Diabetes
43% increased risk of incident
diabetes for every quartile of
Obstructive Sleep Apnea severity
(Botros, 2009)
125-193%
Risk of future obesity in
short sleepers (Gangwisch
2005)
50-150%
Greater risk of short sleepers for developing type 2
diabetes (Gangwisch 2007 & Gottlieb 2005)
Pathways linking sleep loss to insulin
resistance and diabetes
Sleep apnoea
Sleep loss
Hypoxia
Elevated
sympathetic
activity
Inflammation
Diabetic autonomic
neuropathy
Insulin
resistance
Diabetes
Source: McDermott R. Diabetes Management, 2012
“Lifestyle choices”
Disordered
appetite
regulation
Mechanical
airway
obstruction
Obesity
Various theories 4:
The gut micro-biome
• Our gut hosts billions of microorganisms which
contain more than 150 times the genetic diversity
of the human genome
• The micro-biome performs digestive and
metabolic functions, and “evolves” over our life
course
• The micro-biome “talks” to the liver, the brain,
organs controlling metabolism, inflammation and
the immune system
• The micro-biome is affected by what we put into
our mouths
The gut micro biome has a regulatory function on host energy metabolism.
Source: Krajmalnik-Brown R et al. Nutr Clin Pract 2012;27:201-214
Effect of Intestinal Microbial Ecology on the Developing Brain
JAMA Pediatr. 2013;167(4):374-379. doi:10.1001/jamapediatrics.2013.497
Enteric nervous system, providing bidirectional communication between gastrointestinal cells and the central nervous system.
Intestinal epithelial cells mediate interactions between gut bacteria and the central nervous system or the immune system. As
bacteria (shown in green) in the intestine come into contact with receptors (shown in black) on the intestinal wall cell surface, the
receptors transmit signals to the central nervous system via the vagus nerve pathways (curved arrow to central nervous system)
and to the immune system (curved arrow) via Toll-like receptor pathways.
Disruptions to the gut microbiome
• Diet: eg High fat diet is associated with reduced
microbiome diversity
• Disease states: Mainly association studies (causal
direction unclear) for diabetes, some cancers, obesity,
“irritable bowel”, others
• Antibiotics: Effects are immediate and potentially
long lasting, especially important for children
• Bariatric Surgery: Rapid changes in food intake,
metabolism (including reversal of T2diabetes), fat
mass, inflammation, microbiome composition.
What to do?
• BAU – we go broke
• One solution? Unlikely
• Unhelpful sloganeering and ideological corners:
“nanny state”, “personal responsibility” and the
role of government
• Technical individual-level solutions? Eg Bariatric
surgery, various diets combined with sustainable exercise
• Society-level solutions: town planning (active
transport and healthy food supply), workplace re-design,
taxation and regulation.
High Risk & Population
Approaches to Prevention
Truncate high risk end of
exposure distribution (e.g.
organise an obesity clinic).
Clinical approach to disease
prevention.
Reduce a small amount of risk in a
large number of people (e.g. reduce
fat a little in fast-food outlets).
Lifestyle change plus environmental
approach.
…and finally,
Eat food,
mostly plants,
not too much
Michael Pollan, “What to eat”