The instant something sweet touches your tongue, your taste buds direct-message your brain: deee-lish. Your noggin's reward system ignites, unleashing dopamine. Meanwhile, the sugar you swallowed lands in your stomach, where it's diluted by digestive juices and shuttled into your small intestine. Enzymes begin breaking down every bit of it into two types of molecules: glucose and fructose. Most added sugar comes from sugar cane or sugar beets and is equal parts glucose and fructose; lab-concocted high-fructose corn syrup, however, often has more processed fructose than glucose. Eaten repeatedly, these molecules can hit your body...hard.
- It seeps through the walls of your small intestine, triggering your pancreas to secrete insulin, a hormone that grabs glucose from your blood and delivers it to your cells to be used as energy.
- But many sweet treats are loaded with so much glucose that it floods your body, lending you a quick and dirty high. Your brain counters by shooting out serotonin, a sleep-regulating hormone. Cue: sugar crash.
- Insulin also blocks production of leptin, the "hunger hormone" that tells your brain that you're full. The higher your insulin levels, the hungrier you will feel (even if you've just eaten a lot). Now in a simulated starvation mode, your brain directs your body to start storing glucose as belly fat.
- Busy-beaver insulin is also surging in your brain, a phenomenon that could eventually lead to Alzheimer's disease. Out of whack, your brain produces less dopamine, opening the door for cravings and addiction-like neurochemistry.
- Still munching? Your pancreas has pumped out so much insulin that your cells have become resistant to the stuff; all that glucose is left floating in your bloodstream, causing prediabetes or, eventually, full-force diabetes.
- It, too, seeps through your small intestine into the bloodstream, which delivers fructose straight to your liver.
- Your liver works to metabolize fructose—i.e., turn it into something your body can use. But the organ is easily overwhelmed, especially if you have a raging sweet tooth. Over time, excess fructose can prompt globules of fat to grow throughout the liver, a process called lipogenesis, the precursor to nonalcoholic fatty liver disease.
- Too much fructose also lowers HDL, or "good" cholesterol, and spurs the production of triglycerides, a type of fat that can migrate from the liver to the arteries, raising your risk for heart attack or stroke.
- Your liver sends an S.O.S. for extra insulin (yep, the multitasker also aids liver function). Overwhelmed, your pancreas is now in overdrive, which can result in total-body inflammation that, in turn, puts you at even higher risk for obesity and diabetes.