Where are the blind fat people?

According to a friend, there have been studies linking obesity with an inability to recognise real hunger symptoms:

“…these doctors did these tests…locked one group of normal weight people in a room, and another group of obese people in another. gave both groups only a simple sugar syrup to eat. the normal group ate their usual daily caloric intake of the syrup; ate when they were hungry. the obese people, lacking visual cues, ate hardly anything at all. ”

The implication being that the obese people were becoming hungry primarily through visual cues.