 However, Neel argued that "...the concept of a "thrifty genotype" remains as viable as when first advanced...".He went on to advance that the thrifty genotype concept be thought of in the context of a "compromised" genotype that affects several other metabolically-related diseases.Neel in a 1998 review described an expanded form of the original hypothesis, diabetes being caused by "thrifty genes" adapted specifically for intermittent starvation, to a more complex theory of several related diseases such as diabetes, obesity, and hypertension (see also metabolic syndrome) being caused by physiological systems adapted for an older environment being pushed beyond their limits by environmental changes.