The endocrine system is a bit more roundabout in it’s signaling mechanisms. For example, as soon as sugar or carbohydrate hits your tongue, your brain senses that glucose and energy are incoming and thus prepares the body to take care of it. In a nutshell:
Carbohydrate hits the tongue and:
—> Your brain senses and sends electrical impulses to all of your organs to prepare for the incoming sugar load.
—> Salivary amylase is produced/released to help digestion of the carbohydrates in the mouth.
—> Simultaneously, your brain sends signals to your gut to release hormones known as incretins, which stimulate the release of insulin to deal with the incoming sugar load long before the sugar actually reaches your bloodstream. Keep in mind, the carbohydrate is still in your mouth while all this is happening.
—> You swallow (tee-hee). There is no further carbohydrate digestion in the stomach, so it moves to the small intestine upon which time other amylases are released, which break the carb down to it’s smallest constituents to be absorbed.
—> Once the absorbable carbohydrate is in the blood stream, insulin continues to be released to drive the excess sugar into fat and muscle cells in order to keep your blood sugar in a good range (thanks homeostasis!)
—> Once undigested carbohydrates (fiber) reach the large intestine, (generally) good bacteria will use them as fuel and, as byproducts, create mucin, butyrate, and other helpful substances for the colon.
—> Satiation hormones are released to tell your brain that you’ve had enough to eat (CCK, somatostatin)
—> In a timeframe that could be deemed “Soon to hours to a day afterwords” (depending on the individual) leptin rises in accordance with carbohydrate consumption to tell your body that it has enough energy.
This is the extremely simplified version. Sound complex? Its actually much moreso than the above.
I illustrated the above to say that when your body isn’t functioning at its peak, any one of the aforementioned mechanisms could be breaks in your metabolic chain.
Insulin resistance is common in obesity; this is the inability for your cells to recognize the incoming insulin signal and therefore your body needs to release more insulin to get the same job done.
Leptin resistance is another common phenomenon in obesity; generally, the higher your fat stores, the higher your leptin concentration (fat is an endocrine organ, too!). In effect, this should signal the brain to eat less. The overall aim of leptin is as a long-term energy regulator. It tells you to eat less. However, again, in obesity, although leptin concentrations in the blood are extremely high due to high fat mass, the brain becomes resistant to the signal and doesn’t see it, and as a result, you keep eating and keep getting fatter.