It seems that it is common knowledge these days that sugar is really bad for you and should be avoided, but many times the reasons given for doing so are vague. Sugar is so common an ingredient it is scary: it is present in literally almost everything that is edible, so it is super easy to go over the daily recommended limit—about 24 grams for women and 37 for men

Sugar

Moyan_Brenn on Flickr

A word about sugar:

"Good" sugar is naturally occurring. This includes fructose (often found in fruit) and lactose (found in dairy), among others. It is not harmful in small amounts.

"Bad" sugar is added sugar, and the main reason that it is bad is because it contains extra calories and no nutritional value.

1. Adverse Health Effects

sweet, candy
Christin Urso

"Bad" sugar has been linked to diabetes, fatty liver disease, cancer, weight gain/obesity, heart disease, increased risk of stroke and heart attack, among other things.

2. Depression

There are more and more studies being done that increasingly show that "bad" sugar can cause depression, a troubling finding, considering that often it is sugary comfort foods that we gravitate to when we feel sad.

3. It Depletes Your Energy

Sleepy

Lianne Viau on Flickr

Sugar is a necessary component of our diet. It provides energy, but not in the way you might think. It is metabolized in our bodies to become glucose, which our cells use as energy. Sugar does not, however, provide lasting energy, which is why energy drinks also have caffeine. The brain does need sugar to fuel it, but too much quickly causes adverse effects.

4. Brain Drain

Brain

dierk schaefer on Flickr

High levels of glucose for extended periods of time wreak havoc on the brain. It can age cells (this extends to other cells, too, like the ones in your face) and impair cognitive and memory function (bad news if you're trying to pass class). 

5. It's Addictive

Addicted

Capt' Gorgeous on Flickr

How addictive is sugar? Well, when lab rats were given the choice between saccharin (an FDA-approved artificial sweetener) and intravenous cocaine (COCAINE!) they chose the sugar. How many of them chose sugar over an illegal drug that is known to be highly addictive? 94 percent

Remember, natural sugar is an important part of a healthy diet. The problems only occur when you consume too much of it, and it comes from added sugar. While nutritional labels do not differentiate between sugar that is naturally occurring versus added, you can read the ingredients list, and if sugar (or one of its many names) is on that list, then it has been added. 

Avoiding processed food as much as possible is a good rule of thumb. Artificial, no-calorie and no-sugar sweeteners also have their cons, so it is better to avoid these, too