Body Weight Set Point Theory
Do We Have a "Weight Thermostat?
In 1983, William Bennett and Joel Gurin, both physicians, published a book titled "The Dieter's Dilemma: Eating Less and Weighing More" in which they argue that human body weight is "set"
or pre-determined by an internal "fat thermostat". The theory holds that when body weight drops below the set point, the "fat thermostat" causes a drop in caloric output and an increase in
appetite until body weight has climbed to the set point again, at which time caloric intake and output normalize. They postulate a mechanism involving neurochemistry and hormones.

Set point is a theory to explain why long term weight loss appears terribly difficult for many people, even those who manage to lose in the short term. The way I usually attempt to explain
the idea of set point is through an analogy: Imagine a house in the winter when it is very cold outside. The owner has set the thermostat that controls his natural gas heating system to 80
degrees farenheit. This requires a lot of gas flow and it's too hot to be comfortable, so after a time, the homeowner decides to lower the temperature to 70 degrees. He can do this two
ways.

The smart way to lower the temperature is to turn the thermostat down to 70 and wait. Because of heat loss through the walls, the temperature falls in a half hour to 69 degrees. This
causes the heater to kick back on, but only until the the temperature rises to 71 degrees. Then it turns off again---or better yet, the heater can stay on all the time, but turn down it's
flame and gas flow to precisely the levels needed to maintain 70 degrees. THAT is the smart way to lower the temperature.

The dumb way to lower the temperature is to leave the thermostat set for 80, leave the gas flow and the fire on high, but start opening doors and windows to the outside winter air. This
will indeed cool the house, and if one leaves just the right number of windows open, the temperature will stay at 70 even though the thermostat "thinks" it should be 80 and the gas is on
high. Obviously this is a stupid way to cool a home in winter because it is wasteful and because it is fighting the thermostat and the heater the whole time.

Now, if instead of a house, we take a human being and instead of trying to lower temperature, we are trying to lower body weight and instead of gas flow we have calorie intake that is
governed by hunger that is in turn largely controlled by a hidden thermostat, perhaps the idea of set point becomes more clear. As long as we don't lower the "thermostat", we can lose
weight, but it really is a lot like opening all the doors. The thermostat begins to make us very hungry, trying to increase calorie intake, although with enough strength of will, we can
overcome that hunger....for a while just as we can sit in the house with all the doors open. But this really isn't a great way to cool a house and it certainly is a lousy way to lose weight. I
have illustrated the house analogy below.

Is the Set Point Theory Valid?

To some degree, it probably is. We know that when fat cells shrink they can trigger the release of appetite-increasing hormones and thereby act as a sort of thermostat for weight.
We also know that some approaches to weight loss, like semi-starvation can trigger a drop in metabolic rate.

Can the "Fat Thermostat" be Turned Down?

Ten years ago, the answer would likely have been "no" or "maybe". Today, there is strong evidence that the human body can indeed comfortably adjust to a lower body weight. This
evidence comes from patients who have undergone bariatric surgery. Perhaps surprisingly, proceedures like banded gastroplasty that reduce stomach volume do not leave people
forever hungry but anable to eat enough to satisfy. Instead, patients report no intense hunger. This seems to be a result of "shrinking" the stomach which causes cells in the stomach
to signal the brain (via hormone-like proteins) to turn off hunger sooner.
There is a smart and a dumb way to cool a house in winter. The smart way is to turn down the thermostat. The dumb way is to NOT turn
down the thermostat but instead open doors and windows to the outside until the tempertature reaches 70 degrees.
Likewise there is a smart and a dumb way to lose weight. The smart way is to turn down the "weight thermostat". The dumb way is to
drastically lower calorie intake and try to starve oneself into thinness.
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