Evolutionary Hacks? Why Everything We Know About Salt May Be Wrong 

The article in the NYT on some new research results (replication needed) about how our bodies react to salt made no guesses as to why we might produce glucocorticoid hormones that makes us break down fats and muscle tissue.  I cannot help but wonder if this is an evolutionary hack for seasonal regulation of body fat, especially for animals that evolved in environments where salt is not readily available (e.g., traveling to salt licks is required) and thus there is relatively little dietary changes in the amount of salt consumed.

The reason for this is as follows: if fresh water is plentiful but salt is not, then animals tend to struggle to get enough salt.  When salinity increases it would not generally be due to excess consumption, but rather to dehydration.  Dehydration often occurs when an animal sweats, due to thermal stress.  And so using saline levels to control a process to rid the body of excess insulation—as well as making water as a byproduct—would work just as well as using more direct thermal regulation feedback.

Assuming that the original data is good, this implies sitting in saunas do not help much to lose weight, unless we sweat and become dehydrated.  (This is not an experiment that should be done without a great deal of care, obviously, because dehydration can be dangerous.)  Other experimental parameters could be actually measuring the degree of dehydration, the duration it is experienced, etc, versus variations where the subject just consumes more salt (also potentially dangerous due to how sodium may affect blood pressure) to see how a body's salinity level may affect weight.

Are there purely observational experiments that could be more easily conducted?

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