Have you ever eaten when you weren’t hungry? Have you ever finished your entire dessert even though you felt full after the main course? Chances are, you answered yes to both questions. Many Americans are in permanent “feast mode,” and frequently eat past the point of fullness. Why is this the case? The hormone leptin is part of the answer.
Leptin is released by your fat cells, to tell your brain how much fat you have, and to signal fullness. The intended effect of leptin is to inhibit food intake and encourage energy expenditure (exercise). However, when the brain is repeatedly flooded with leptin, a phenomenon known as leptin-resistance can ensue. Most overweight and obese Americans have some degree of leptin-resistance.
As we learned last week, sugar - especially fructose - interferes with satiety, and it does this in part by interfering with the activity of leptin. This makes sense from an evolutionary standpoint. It was advantageous for our ancestors to eat plentiful sugar in the summer and fall, to store fat (energy) for the scarce winter. We now live in a time and place of ample resources, so we must be mindful of how much and what types of food we consume if we are to stay healthy.
Most people are not born resistant to leptin. We know when we are full. We have a very functional system in place, but if we repeatedly ignore the signals from our brain, imbalances can occur. Listen to your body, and if do you choose to eat sugar, be aware that your brain may not receive the signals of fullness that it otherwise would.