Presentation on theme: "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."— Presentation transcript:
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 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
25 50 % Communicable diseases, maternal and perinatal conditions and nutritional deficiencies Injuries DALYs, by broad cause group in Developing Countries (baseline scenario) DALY = Disability adjusted life-year Source: WHO, Evidence, Information and Policy, 2000 Noncommunicable conditions
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), Source: McDermott et al, AHR 2003
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), 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 :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
Source: Sellayah D, et al “On the evolutionary origins of obesity: a new hypothesis. Endocrinology 2014:doi: en Human migrations and metabolic adaptation to different environmental stressors: a new theory for ethnic obesity variation
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
Sugar consumption and obesity prevalence in the USA, Source: Johnson et al, 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
Energy cost and food prices $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) New York Times, 10 / 99 Chronic short sleep has consequences for health
Sleep, Obesity and T2 Diabetes % Risk of future obesity in short sleepers (Gangwisch 2005) % Greater risk of short sleepers for developing type 2 diabetes (Gangwisch 2007 & Gottlieb 2005) 43% increased risk of incident diabetes for every quartile of Obstructive Sleep Apnea severity (Botros, 2009)
Pathways linking sleep loss to insulin resistance and diabetes Sleep apnoea Sleep loss“Lifestyle choices” Elevated sympathetic activity Insulin resistance Diabetes Hypoxia Inflammation Obesity Diabetic autonomic neuropathy Mechanical airway obstruction Disordered appetite regulation Source: McDermott R. Diabetes Management, 2012
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:
Effect of Intestinal Microbial Ecology on the Developing Brain JAMA Pediatr. 2013;167(4): doi: /jamapediatrics 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.
…and finally, Eat food, mostly plants, not too much Michael Pollan, “What to eat”