In the 1970’s, researchers removed the ovaries of healthy, normal weighted rats who had unlimited access to food. After the surgery the rats became ravenous, ate far more food then was necessary and became obese.
At first glance, this seems logical – eat more then you need, you get fat. Not that interesting.
It’s the follow-up study, though, that really makes for an interesting story. The researchers again removed the ovaries of healthy, normal weighted rats, but this time put them on a calorie restricted diet. According to conventional wisdom, this should have solved the weight gain problem. It didn’t. In fact, the rats still became obese. The difference was they also became completely sedentary. They only moved to eat.
It seems as if the rat’s new physiology (resulting from having the ovaries taken away) changed the amount of fat the body “wanted” to store – it changed the fat regulation. To reach the new fat “set point”, the rats compensated by eating more, or if that wasn’t an option, moving less.
The physiology, in other words, created the behaviour, the behaviours did not create the physiology. They ate more or moved less because they were storing fat…not the other way around.