In 1951, Brobeck and his colleague Bal Anand reported that lesioning a different region of the hypothalamus—the lateral hypothalamus—would induce rats to stop eating and lose weight and even die of starvation. Ranson’s lab had reported this phenomenon in rats, cats, and monkeys in the 1930s, but now Brobeck and Anand reinterpreted it to support Brobeck’s belief that the hypothalamus regulates eating behavior. Brobeck proposed that the lateral hypothalamus is a “feeding center” that motivates animals to eat, and the ventromedial hypothalamus works as a “satiety center” to inhibit eating.

In August 1942, just three months after Ranson and Hetherington published their research, Ranson died of a heart attack. If there was a single event that derailed the course of obesity research in the United States, this may have been it. With World War II raging and his adviser gone, Hetherington left Northwestern to do research for the U.S. Air Force. This left Brobeck, still a medical student at the time, as the leading authority on these experiments, and so it was Brobeck’s emphasis on overeating—hyperphagia—as the cause of the obesity in these brain-damaged animals that dominated thinking in the field, despite its inability to explain the observations. Though later editions of Ranson’s textbook The Anatomy of the Nervous System would continue to refer to the ventromedial hypothalamus as a regulator of fat metabolism, the investigators writing about human obesity would refer to the VMH as a regulator of hunger and ingestive behavior.

Once human-obesity research became the domain of psychologists and psychiatrists in the 1960s, studies of hypothalamic obesity left behind once and for all the greater context of homeostasis and the use and storage of metabolic fuels, and focused instead on how Brobeck’s dual centers of the hypothalamus allegedly regulate eating behavior. This served to further the conviction that defects in this region of the brain cause overeating, and overeating causes obesity. Hunger, and the overeating that accompanies it, would be considered exclusively a psychological phenomenon, not a physiological one. (Because these psychologists would consider eating behavior to be the subject of their research, they would often screen their animals after surgery and those that didn’t eat voraciously would be “discarded.” They would then omit these animals from their subsequent analyses, even if the discarded animals became obese as well.) Hunger was something that occurred only in the head, and so it could be decoupled from the needs of the body, at least with sufficient willpower.