These days, everything from vitamin water to beef jerky contains added sugar (sugar that was not naturally a part of the food or beverage, but was instead added during processing and production.) This added sugar isn’t natural, no matter how companies label it and try to convince people that it is. If you extract sugar (fructose) from an apple, and add that to a protein bar, that bar has added sugar. But if you cut up the whole apple instead and place it inside of the bar, without adding any refined sweeteners, that bar is naturally sweetened. Your body will process the apple’s vitamins, nutrients, and fiber along with the apple’s natural sugar, and your body will benefit from it.
Once inside of your body, the sugar seeps into your bloodstream, causing your pancreas to secrete insulin, in order to get the sugar to the cells that need it. This would normally level out your blood sugar, but many processed foods contain so much added sugar that it can’t be used all at once. The excess sugar is converted into fat and stored in your body. Over time, with a diet high in added sugar (daily sodas for instance), your body stores up more and more fat - not just around your middle, but in and around vital organs like your heart and liver. This is where things get very serious; this buildup of fat can lead to diabetes, heart disease, liver disease, cancer, and many other health issues.
Bottom line: don't do away with the benefits of whole fruits in your bid to implement a sugar-free diet!