Naturally contained sugars in fruit and vegetables are balanced by the fiber, vitamins, enzymes and other properties of the fruit/vegetable which slow sugar digestion and help the body deal with it more easily. Processed varieties, on the other hand, provide none of these benefits and instead create these harmful effects of sugar in the body:
Effects on Your Brain
Eating sugar gives your brain a huge surge of a feel-good chemical called dopamine, which explains why you’re more likely to crave a candy bar at 3 p.m. than an apple or a carrot. Because foods like fruits and veggies don’t cause the brain to release as much dopamine, your brain starts to need more and more sugar to get that same feeling of pleasure.
Your Mood
The occasional candy or cookie can give you a quick burst of energy (sugar high) by raising your blood sugar levels fast. When your levels drop as your cells absorb the sugar, you may feel jittery and anxious. But if you’re reaching into the candy jar too often, sugar starts to have an effect on your mood.
Liver
It overloads and damages your liver. The effects of too much sugar or fructose can be likened to the effects of alcohol. All the fructose you eat gets shuttled to the only organ that has the transporter for it: your liver. This severely taxes and overloads the organ, leading to potential liver damage.
Weight
It tricks your body into gaining weight and affects your insulin and leptin signaling. Fructose fools your metabolism by turning off your body's appetite-control system. It fails to stimulate insulin, which in turn fails to suppress ghrelin, or "the hunger hormone," which then fails to stimulate leptin or "the satiety hormone." This causes you to eat more and develop insulin resistance. It causes metabolic dysfunction. Eating too much sugar causes a barrage of symptoms known as classic metabolic syndrome. These include weight gain, abdominal obesity, decreased HDL and increased LDL, elevated blood sugar, elevated triglycerides, and high blood pressure.
Sugar also affects the body by:
Increasing Bad Cholesterol and Triglycerides
Contributing to Leptin Resistance (and then weight gain, cravings, sleep trouble, etc.)
Creating an addictive sugar response in the brain
Not filling you up and instead encourages you to eat more