Thrifty genes a development dilemma

I’ve been reading Ellen Shell’s The Hungry Gene: The Inside Story of the Obesity Industry. It provides a potted history of discoveries that confirm the genetic basis for obesity and is chatty, good light reading. One interesting observation that was new to me was the notion that obesity and associated Type 2 diabetes problems were particularly likely to arise in societies previously subject to food stresses and where, as a result, 'thrifty genes', had emerged to ensure survival in difficult times. Problems then arise if people come into contact with an abundant, sustained rather than periodic food supply.

Thrifty genotypes were constellations of genetic factors that encourage the conversion of calories into body fat and which decreased the sensitivity of the body to insulin to ensure adequate blood glucose levels in the brain during famine. This mechanism was essential for people to survive 'bottleneck' periods of extreme stress and food scarcity. ‘Thrifty genes’ became essential for survival given the ebb and flow of food availability.

Westernisation of such societies and their transition to stable, reliable food supplies means that the genes which once protected now condemn people to early deaths through obesity and diabetes illnesses. It is not what such people eat – those among them who have white ancestry, because of interbreeding of locals with randy early European settlers, have much lower incidence of such diseases though they share a common diet.

This story has one dramatic implication. Western societies have severe obesity-diabetes problems but these problems are not nearly as bad as societies which have had a history of food stresses. Examples of such societies include indigenous populations (e.g. the Australian aborigines, Hawaiians, Samoans, Nauruans) – where up to half the population is obese with diabetes - and those from Middle East cultures and the Sub-Continent.

More generally, an improved food situation in Asia and Africa might have dramatically adverse health consequences if these societies have previously been food stressed. The emergence of obesity issues in China and India suggests this is already a problem. Thus, the replication of the Western global obesity epidemic might be expected to have much more dramatic health implications in newly-emerging and developing countries.