The supermarket is an awesome place to school your kids on healthy eating. But it can get heated if you happen to be in the cookie aisle. Recently, my son and I were rolling our cart past those sugary squares and disks and double-stuffed whatevers when he informed me that his friend gets seven cookies in his lunch every day. (My kids get two, max. After dishes and homework.)
I saw my opening. "Well, let me tell you about nonalcoholic fatty liver disease," I said. Too soon for a 12-year-old? Heck no! I'll tell you what I told him: Overdo the cookies or other sugary foods, and your liver takes the fructose hit.
Located on the right side of your abdomen, tucked behind your lower ribs, your liver has a critical job: to turn toxins—both those formed naturally in the body and those that are man-made, such as from medications, street drugs, and alcohol—into harmless substances.
The liver uses about 20 percent of the calories you consume to fuel itself and its work, which includes converting proteins and sugars from food into energy for your body, aided by insulin.
Related: The Best Foods For Your Liver 
A steady diet of fructose-laden foods can cause globules of fat to begin to form in the cells of the liver. Before 1980, doctors rarely saw this fatty buildup, known as nonalcoholic fatty liver disease (NAFLD). Now, it affects 30 percent of US adults. It's worth noting that the rise in the incidence of NAFLD parallels the increase in obesity and diabetes, and that the condition affects between 70 and 90 percent of those who are obese or have type 2 diabetes. In fact, experts consider NAFLD to be a hallmark of metabolic syndrome, a condition characterized by a cluster of obesity-related conditions.
This buildup of fat in the liver isn't necessarily obvious on your thighs. A 2012 study in the American Journal of Clinical Nutrition found that people who ate 1,000 extra calories of sugary foods for 3 weeks saw just a 2 percent increase in body weight, but a 27 percent increase in liver fat.
Related: 11 Weird Things Sugar Is Doing To Your Body 
When you lose weight, liver fat returns to normal levels. But if NAFLD isn't caught in time, the liver can become inflamed, which can lead to a more severe liver condition known as nonalcoholic steatohepatitis (steato means fat, and hepatitis is liver inflammation).
If the inflammation becomes severe enough, scar tissue replaces healthy tissue, impairing the liver's ability to perform its many crucial functions. When that happens, it's called cirrhosis. (Cirrhosis only happens with really severe alcoholism, right? At least that's what I always thought. Now, it appears, an excessively sugary diet could play a role, too. Amazing.)
A fat-riddled liver may become resistant to the action of insulin. As the pancreas churns out more and more of this fat-storage hormone to prod the liver into doing its job, insulin levels increase—and so does body fat.