One fattening food that may shock you because it is thought to be "healthy" is -- fruit juice.

Most fruits are VERY healthy for us. However, we
were NOT meant to separate the juice from the rest of the fruit and
only drink the high calorie sugary mixture and leave behind the
fiber and other beneficial components of the fruit.

When you only drink the juice of fruits (apple juice and orange
juice being 2 of the worst culprits in the western diet), you are
not getting the appetite satisfying effect of the fiber in the
fruit, and you're left craving more carbs. Also, the fiber in
whole fruit helps to slow the blood sugar response when eating
whole fruit compared to fruit juice.

Bottom line... over consuming fruit juices makes you fat. On the
other hand, eating whole fruits including all of the fiber helps
you maintain a healthy balanced diet and high nutrient density (as
long as the rest of your diet is whole unprocessed foods as well).