Remember when you were a kid and your tried to see how long you could hold your breath? It was as easy at first, but after about 30 seconds, respiratory control centers in your brain reacted to falling oxygen levels in your blood and told you in no uncertain terms you needed to breathe. Maybe you thought you could control your breathing better than that, but you really couldn’t. Mother Nature showed you who’s boss
A similar thing happens when you try to reduce the amount you eat. It’s easy at first, but it quickly gets harder. Just as the breathing centers in your brain respond to reduced oxygen in your blood, appetite control centers in your brain sense a lack of food in your system. If you try to eat less, these centers will tell you to eat more. They can also sense when you’ve eaten too much and react by curbing your appetite; at least that’s how it’s supposed to work. However, if you are overweight, those centers are telling you to eat even though you have plenty of calories in your system stored up as fat.
Whether your brain tells you to eat more or eat less is determined by the balance among several hormones, some of which promote weight gain and some of which promote weight loss. An example of a hormone that promotes weight gain ghrelin. If your stomach is empty too long, it secretes Ghrelin into the bloodstream. Ghrelin travels to your brain and stimulates hunger. An example of a hormone that promotes weight loss is leptin, which is secreted by your fat cells. It suppresses appetite. The more fat you have, the more leptin you secrete and the more it should suppress your appetite.
Like leptin, GLP-1s job is to keep you from gaining too much weight. It does this in three ways: It keeps food from being digested too fast. It prevents nutrients in your blood from turning to fat and it calms the hunger centers in your brain.
Calming an Overactive Digestive System
One of the ways the appetite control centers in your brain control your weight is by limiting the amount of food you can put in your stomach. Your stomach acts as sort of a storage bin, or hopper, which regulates how fast food enters your intestine where it is absorbed into the bloodstream. How fast food leaves your stomach is controlled by a muscular ring wrapped around the exit of the stomach, called the pyloric sphincter. When the muscle tightens it constricts the outlet of stomach, which slows the speed with which food leaves the stomach and enters the intestine. This promotes a feeling of fullness, which sends a signal to your brain to stop eating.
Folks who are overweight often digest their food too quickly. Their stomachs empty too fast, so they need more food to make them feel full. They also get hungry sooner after meals. By slowing stomach emptying GLP-1 medications promote more satisfaction with less food and delays the return of hunger after eating.
Keeping Nutrients in the Blood from Turning to Fat
Once in your bloodstream, nutrients are either used to provide energy or are converted to fat by specialized cells called fat cells. Overweight folks turn the nutrients in their bloodstream to fat too rapidly. Their fat cells suck up nutrients too quickly so fewer nutrients reach the brain. Their appetite is harder to satisfy, and hunger returns sooner after eating.
GLP-1 keeps nutrients from being taken up by fat cells too quickly. It does this by reducing the amount of insulin in your blood. One of insulin’s jobs is to transport nutrients in your blood into your fat cells. The amount of insulin you produce is governed by the level of sugar is in your bloodstream. Although most of the sugar in your system comes from eating carbohydrates, your liver produces sugar. It generally doesn’t produce much because there’s usually plenty of carbohydrates in the diet. It may not seem to make sense, but overweight folks’ livers produce more than normal amounts of sugar even though there’s plenty of it in the diet. GLP-1 counteracts that. It reduces the amount of sugar the liver produces. Less sugar means less insulin; less insulin means fewer calories being pushed into your fat cells and more going to your brain to satisfy your hunger.
Calming the Hunger Centers in Your Brain
Ultimately, how much you eat is controlled by centers in your brain. In addition to slowing stomach emptying and reducing the amount of sugar your liver produces, GLP-1 acts directly on these centers to curb your cravings for food. One of side effects of GLP-1 medications is nausea. This usually occurs if the dose is increased too fast and is usually temporary. Studies have shown that the weight loss from GLP-1 medication is not dependent on it causing nausea.
