Thrift: a guide to thrifty genes, thrifty phenotypes and thrifty norms

Abstract

There is a growing interest in evolutionary models of human adiposity. Frequent reference has been made to 'thrifty genes' or 'thrifty phenotypes', referring to a variety of metabolic or behavioural traits that in one or the other way imply frugality in the expenditure or storage of energy. However, there is confusion over how the strategy of thrift has been incorporated into human biology. At the broadest level, humans represent a thrifty species relative to other mammals, indicating that metabolic adaptations had a crucial role in the emergence of the Homo lineage, in particular in buffering reproduction from ecological stochasticity. In contemporary humans, some variability in adiposity may be attributable to genotypes systematically favoured in certain ecological settings. Genetic variability is also present within populations, and may be considered bet hedging (distributing risk across offspring to increase parental fitness). Bet hedging is an alternative to genetic drift for accounting for genetic variability in the absence of strong selective pressures. Contrasting with genetic variability emerging over the long-term, thrifty phenotypes represent a response to short-term ecological variability. Physiological plasticity allows the emergence of variability across the life course in response to ecological cues experienced directly or by very recent ancestors. Finally, cultural norms or individual preferences allow voluntary behavioural manipulation of thrift in individuals. Overall, there is a range of factors and processes both favouring and opposing thrifty genes, which may reflect moderate bet hedging rather than systematic adaptation. Plasticity protects the genome from selective pressures by tailoring the organism to ongoing ecological conditions. The fact that obesity can occur in different individuals through different genotypes, life histories and behaviours indicates that different treatments are also likely to be required.

Worldwide spatial genetic structure of angiotensin-converting enzyme gene: a new evolutionary ecological evidence for the thrifty genotype hypothesis

“…Although the concept of 'multiple thrifty gene form' has been put forward, the research and discussion scope is still constrained in genes involved in regulation of energy balance. 3,[16][17][18] In the present study, we further extended the concept of thrifty gene, and proposed that genes involved in regulation of water and sodium balance could also be good candidates as thrifty genes. As an impressive case, we selected the ACE gene, a key gene in RAAS, to explore the new evolutionary ecological evidence for the 'thrifty genotype' hypothesis.…”

“…3,16,17 A broader range of traits may merit within this typology, including those relating to growth, reproduction and immune function. 18 Consistent with the multiple possible forms of thrifty gene, we propose that the thrifty gene should not be limited to genes involved in the regulation of energy balance; genes involved in the regulation of water and sodium balance may also be good candidates as thrifty genes.…”

The evolution of body fatness: trading off disease and predation risk

“…It was soon recognised that the key to this argument was fat deposition and, hence, genes unrelated to diabetes that also promote fat deposition would also be 'thrifty genes' and selected for. As a result, the idea developed into an evolutionary explanation for the genetic basis of obesity, as well as type 2 diabetes (Dugdale and Payne, 1977;Chakravarthy and Booth, 2004;Eknoyan, 2006;Prentice, 2001;Watnick, 2006;Wells, 2009Wells, , 2010Wells, , 2012Prentice, 2005).…”

Obesity and energy balance: is the tail wagging the dog?

“…Obesity is not a homogeneous phenotype, and there are multiple pathways to its development (Wells, 2009). But if supported by further experimental evidence, the metabolic perturbation hypothesis can potentially explain a great deal about escalating national and global obesity epidemics, as well as epidemics of associated diseases, and could therefore offer new approaches to public health policies.…”