Table 1. Summary of evolutionary hypotheses for the metabolic syndrome.

Name		Proposed by	Description	Sources
Thrifty gene hypothesis		James Neel	Repeated exposure to famine led to positive selection for genes promoting efficient energy storage.	[12,28]
Thrifty phenotype hypotheses	Barker hypothesis	Charles Hales and David Barker	An undernourished fetus must be “thrifty” with its resources, and sacrifices pancreas development in favor of other tissues.	[45]
	Weather Forecast model	Patrick Bateson	Fetal environment predicts the quality of the childhood environment. Mismatches between fetal and childhood environments lead to disease.	[14,46]
	Maternal Fitness model	Jonathan Wells	Fetal environment uses nutritional signals to align its metabolism with its mothers.	[14,48]
	Intergenerational phenotypic inertia model	Christopher Kuzawa	Intrauterine nutritional signals provide information about long-term nutritional history of the mother and her recent ancestors through epigenetic mechanisms.	[14,62]
	Predictive adaptive response model	Peter Gluckman and Mark Hanson	Fetal environment predicts adult environment and primes metabolism for adult life.	[14,47]
Thrifty epigenome hypothesis		Reinhard Stöger	All humans have a thrifty genotype. Phenotypic expression of this is altered by epigenetic modifications that respond to environmental conditions.	[50]
Behavioral switch hypothesis		Milind Watve and Chittaranjan Yajnik	Insulin resistance is a mechanism for both a switch between r/K reproductive strategies and a switch between soldier/diplomat behavioral strategies.	[15]
Aggression control hypothesis		Prakakta Belsare et al.	Insulin and satiety mediate aggressive and non-aggressive lifestyle strategies.	[63]
Drifty gene/predation release		John Speakman	Genes controlling the upper limit of body weight have been freed from selective constrain and subject to genetic drift.	[9,24,33]
Maladaptation to brown adipose tissue requirement		John Speakman	Obesity is a byproduct of variation in positive selection for thermogenesis.	[13]
Genetically unknown foods hypothesis		Riccardo Baschetti	Obesity and diabetes occurs when populations are introduced to new foods that they haven’t adapted to.	[38]
Fertility first hypothesis		Stephen Corbett et al.	Fertility, rather than starvation, is the main driver of selection for thrifty phenotypes.	[64]