Just read an interview between Gretchen Rubins (have a look on her website for the whole interview) and Gary Taubes who recently published “The Case Against Sugar”. There were lots of good points in it, but I found this bit particularly poignant. Sorry it is so long, I have edited a little for length but not much:
“One likely phenomenon … for why people who are obese or predisposed to be obese would crave carbohydrates and sugar more than someone who is naturally lean. The obese people tend to be insulin resistant, which means that their insulin is going to be elevated. This insulin is not only preventing their fat cells from mobilizing fat, itβs signalling the other cells in their body to burn carbohydrates (glucose) for fuel. So for someone whoβs insulin resistant, carbohydrates are their primary source of fuel. Even when their blood sugar is dropping and they should be burning fat instead, their body wants to continue to burn carbs.
Now these people also tend to secrete too much insulin, and this will happen even before they eat, when theyβre just thinking about eating. This is called the βcephalic phaseβ insulin response, and itβs like a Pavlovian phenomenon. If I start thinking about eating some delicious bread pudding, Iβm not just going to salivate, my pancreas is going to start secreting insulin to prepare my body to deal with that bread pudding as I eat it. The more predisposed we are to put on weight, and the more insulin resistant we are, the greater this response will be.
So now letβs imagine two people, a naturally lean person and a person predisposed to get fat, and they both walk by a bakery. They smell the freshly baked bread and the sweets and theyβll experience entirely different levels of cravings based on how their bodies respond to the stimulusβthe cephalic phase insulin response in particular.
A lean person might have a relatively mild responseββMmm, that smells good,β and he or she just keeps walking. The obese person or the person predisposed to gain weight will have a much different response: the delicious smell will trigger a hormonal responseβinsulinβthat works to lock up fat calories and lower blood sugar, and suddenly that person is almost literally starving, and starving for carbohydrates. The insulin is in effect emptying their blood stream of available fuels. The lean person walks by the bakery proud of his or her willpower. The obese person or the person predisposed to obesity canβt resist walking in, buying the bread or sweets, and eating it. And then feels guilty for not being able to eat in moderation. Itβs physiology driving behaviour, not the other way around.”