association between thinness in birth (measured as Ponderal index) and insulin resistance, the association being independent of length of gestation period, adult body mass index, and confounding factors like then current social class or social class at birth. In 2001, Hales and Barker updated the hypothesis by positing that the thrifty phenotype may be an evolutionary adaptation: the thrifty phenotype responds to fetal malnutrition by selectively preserving more vital organs of the body and preparing the fetus for a postnatal environment where resources will be scarce. Evolutionary rationale Offspring Maternal nutrition can affect the development of the unborn child in poor nutritional environments such that it will be prepared for survival within that poor environment. This results in a thrifty phenotype (Hales & Barker, 1992). It is sometimes called Barker's hypothesis, after Professor David J. P. Barker, researching at the University of Southampton who published the theory in 1990. Metabolic The thrifty phenotype hypothesis says that early-life metabolic adaptations help in survival of the organism by selecting an appropriate trajectory of growth in response to environmental cues. An example of this is type 2 diabetes. In their review, Barker and Hayes discuss evidence that beta cells abnormally develop due to malnutrition during fetal development, causing insulin abnormalities later in life. The review also notes that low birth weight alone does not necessarily mean that it is a manifestation of Thrifty Phenotype. Since low birth weight is not exclusively caused by maternal malnutrition, meaning that other factors could influence the low birth weight- disease relationship. Before the term “Thrifty Phenotype” was coined, Barker had noted the phenomenon with cardiovascular disease. In his lecture paper, he discusses the role of malnutrition during fetal development in Obstructed Lung Disease (now known as COPD), Ischemic heart disease, and blood pressure. In each of these diseases, there was an association with social class and development prevalence of the disease. This was determined to be due to issues of malnutrition during key points in organ development in utero. Benefit for mother However, environmental changes during early development may result in the selected trajectory becoming inappropriate, resulting in adverse effects on health. This paradox generates doubts about whether the thrifty phenotype is adaptive for human offspring. Thus, the thrifty phenotype should be considered as the capacity of all offspring to respond to environmental cues during early ontogenetic development. It has been suggested that the thrifty phenotype is