I dive into one of the most fascinating series of studies I’ve ever come across.
Anyone can lose weight by eating less food. Anyone can be starved thin. Starvation diets are rarely sustainable, though, since hunger pangs drive us to eat. We feel unsatisfied and unsatiated on low-calorie diets. We do have some level of voluntary control, of course, but our deep-seated instinctual drives may win out in the end.
For example, we can consciously hold our breath. Try it right now. How long can you go before your body’s self-preservation mechanisms take over and overwhelm your deliberate intent not to breathe? Our body has our best interests at heart and is too smart to allow us to suffocate ourselves—or starve ourselves, for that matter. If our body were really that smart, though, how could it let us become obese? Why doesn’t our body realize when we’re too heavy and allow us the leeway to slim down? Maybe our body is very aware and actively trying to help, but we’re somehow undermining those efforts. How could we test this theory to see if that’s true?
So many variables go into choosing what we eat and how much. “The eating process involves an intricate mixture of physiologic, psychologic, cultural, and esthetic considerations.” To strip all that away and stick just to the physiologic variable, Columbia University researchers designed a series of famous experiments using a “food dispensing device.” The term “food” is used very loosely here. As you can see at 2:02 in my video 200-Pound Weight Loss Without Hunger, the researchers’ feeding machine was a tube hooked up to a pump that delivered a mouthful of bland liquid formula every time a button was pushed. Research participants were instructed to eat as much or as little as they wanted at any time. In this way, eating was reduced to just the rudimentary hunger drive. Without the usual trappings of “sociability,” meal ceremony, and the pleasures of the palate, how much would people be driven to eat?
Put a normal-weight person in this scenario, and something remarkable happens. Day after day, week after week, with nothing more than their hunger to guide them, they eat exactly as much as they need, perfectly maintaining their weight, as shown below and at 2:36 in my video.
They needed about 3,000 calories a day, and that’s just how much they unknowingly gave themselves. Their body just intuitively seemed to know how many times to press that button, as seen here and at 2:48 in my video.
Put a person with obesity in that same scenario, and something even more remarkable happens. Driven by hunger alone, with the enjoyment of eating stripped away, they wildly undershoot, giving themselves a mere 275 calories a day, total. They could eat as much as they wanted, but they just weren’t hungry. It’s as if their body knew how massively overweight they were, so it dialed down their natural hunger drive to almost nothing. One participant started the study at 400 pounds and steadily lost weight. After 252 days of sipping the bland liquid, he lost 200 pounds, as you can see here and at 3:35 in my video.
This groundbreaking discovery was initially interpreted to mean that obesity is not caused by some sort of metabolic disturbance that drives people to overeat. In fact, the study suggested quite the opposite. Instead, overeating appeared to be a function of the meaning people attached to food, “aside from its use as fuel,” whether as a source of pleasure or perhaps as relief from boredom or stress. In this way, obesity seemed more psychological than physical. Subsequent experiments with the feeding machine, though, flipped such conceptions on their head once again.
When researchers covertly doubled the calorie concentration of the formula given to lean study participants, they unconsciously cut their consumption in half to continue to perfectly maintain their weight, as seen here and at 4:24 in my video. Their body somehow detected the change in calorie load and sent signals to the brain to press the button half as often to compensate. Amazing!
When the same was done with people with obesity, though, nothing changed. They continued to drastically undereat just as much as before. Their body seems incapable of detecting or reacting to the change in calorie load, suggesting a physiological inability to regulate intake, as shown below and at 4:40 in my video. 
Might the brains of persons with obesity somehow be insensitive to internal satiety signals? We don’t know if it’s cause or effect. Maybe that’s why they’re obese in the first place, or maybe the body knows how obese it is and shuts down its hunger drive regardless of the calorie concentration. Indeed, the participants with obesity continued to steadily lose weight eating out of the machine, regardless of the calorie concentration and the food being dispensed, as you can see here and at 5:19 in my video. 
It would be interesting to see if they regained the ability to respond to changing calorie intake once they reached their ideal weight. Regardless, what can we apply from these remarkable studies to facilitate weight loss out in the real world? We’ll explore just that question next.