Causes of Obesity

Obesity is a very busy topic.
This review in Critical Reviews in Food science and Nutrition makes a thorough evaluation of the 10 putative contributors to the obesity epidemic. The review is comprehensive and well worth reading
The obesity epidemic is a global issue and shows no signs of abating, while the cause of this epidemic remains unclear.
The eating energy-dense foods and reduced physical activity are the alleged causes of the epidemic, despite a lack of solid evidence to demonstrate their causal role.
The writers accept that these may contribute to obesity, but propose several alternative putative contributors that would benefit from equal consideration and attention.
Evidence for microorganisms, epigenetics, increasing maternal age, greater fecundity among people with higher adiposity, assortative mating, sleep debt, endocrine disruptors, pharmaceutical iatrogenesis, reduction in variability of ambient temperatures, and intrauterine and intergenerational effects as contributing factors to the obesity epidemic are reviewed herein.
Their questioning of the big two stems from two points. First, the evidence supporting various elements of the big two as contributors to individual or population levels of obesity is often quite weak. Second, even though some elements of the big two do very likely play some role in influencing obe¬sity levels, we believe that an unquestioned assumption of their pre-eminence has led to the possibly ill-advised expenditure of public effort and funds on programs aimed at reducing popu¬lation levels of obesity that has also reduced the exploration of other potential causes and the alternative obesity reduction programs that might stem from their identification.
The big two seem to they have an appeal based, in part, on their simplicity and the fact that they require little specialized knowledge to comprehend and deal with easily observable as-pects of life with which all of us are familiar.
What are some of the specific facts that enhance our scepticism of the big two as near-omnipotent causes of the obesity epidemic?
1. Papers on Restaurant Dining, Physical education , urban life, high fructose corn syrup consumption and vending machines do not support these attractive ideas.
2. Infections and obesity. A number of bacterial infections have been shown in animal experiments to increase weight in the infected host. Fat cells and macrophages have many similar functions and affecting macrophages by infection may influence adipocyte response
3. Epigenetics and obesity There may be environmental influences on our genetic make up.
4. Maternal age older mums, fatter offspring
5. Fat people or rather individuals with a genetic predisposition have more children than those with a lover level of adiposity.
6. Human adiposity levels have a genetic component.
7. Decreased Sleep may influence the mediators of appetite and energy homeostasis
8. Endocrine disrupters and obesity, including plasticizers ( bisphenyl ether and bisphenol A ) which are stable in the environment.
9. Pharmaceutical drugs
10. Ambient temperature

McAllister et al 2009 Ten putative contributors to the obesity epidemic . Critical Reviews in Food science and Nutrition vol 49, 868-913

Martin Eastwood
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