If obesity is always due to one very specific diencephalic deficiency, it follows that the only way to cure it is to correct this deficiency. At first this seemed an utterly hopeless undertaking. The greatest obstacle was that one could hardly hope to correct an inherited trait localized deep inside the brain, and while we did possess a number of drugs whose point of action was believed to be in the diencephalon, none of them had the slightest effect on the fat-center. There was not even a pointer showing a direction in which pharmacological research could move to find a drug that had such a specific action. The closest approach were the appetite-reducing drugs – the amphetamines—– but these cured nothing.
Source: Pounds and Inches Manuscript