English: The Last Supper of Jesus Christ (Photo credit: Wikipedia)
Our stomach, intestines, fat cells, and organs are all linked to our brains through a complex set of appetite signals, and this appetite system is designed to encourage us to gain weight at every opportunity. Our bodies are designed for famine. Not many hundreds of years ago, we humans could survive only if our bodies encouraged us to eat at every opportunity and to eat more than we needed at any given moment. We survived only if our bodies directed us to rest at every resting opportunity, and to move only when the movement helped us to eat or stay out of danger.
Because of this survival system, we feel hungry whenever we see, hear, smell, or think about food. We can blame this overactive hunger response on a hormone called ghrelin. This hunger hormone, produced in the intestine, rises at meal times, when you see food, when you smell food, when you think about food, or when you see food on TV. Ghrelin is what makes your stomach feel empty. It travels to the brain and says, “Feed me.”
When ghrelin rises, it’s hard to talk yourself through the hunger you feel. You may have just eaten. It may not be rational that you feel hungry, but you do. So you eat.
Food hits your stomach and intestines. As the stomach fills out and expands, nerves register the sensation of being stretched and send the brain the signal “I’m full.” Other chemicals, including a hormone called leptin that is released from your fat cells, confirm this message, telling the brain, “We’re really full now.” They also tell the stomach to stop sending food into the back logged intestine and tell the pancreas to make insulin to shuttle blood sugar into cells. The problem is that these signals are sluggish and they don’t travel quickly. It takes 10 to 20 minutes for these signals to reach the brain with the “I’m uncomfortably full” message, and, for most people, that’s too late. The sluggish response allows us to wolf down much more food than our bodies need at any given time, especially if we are eating quickly.
Depending on what we’ve just eaten and how quickly the food moves through the intestines, these fullness signals can be fleeting. Once they tell the brain, “I’m full,” fullness signals dissipate, which is why we’re all capable of feeling hungry within minutes after eating large amounts of food, especially if we have an ice cream sundae sitting in front of us.
As soon as you gain just a little bit of weight or throw the system off with too much stress or too much of the wrong types of foods, these messages from the various hunger and fullness hormones get distorted. The hunger hormones grow stronger and the fullness hormones grow weaker. Leptin and insulin levels remain chronically high, and the brain stops listening to them. Instead, appetite signals keep getting through, and you continue to feel hungry, even when you shouldn’t. According to the signals that are getting through to your brain, you are “starving,” and we mean that literally. Even though you are actually gaining weight, your brain is getting the message that you are wasting away, so it directs your stomach to rumble at every opportunity.
Muscle cells stop responding to insulin, so insulin has no choice but to usher calories into fat cells. This survival system worked well for us when our next huge meal might be days or weeks away. It doesn’t help us out so much today, however, when our next meal is as close as the refrigerator.
What helps? I’ll tell you next week.
