Fruits.
Fruits are very unique, they have sweet taste but they behave so much different from metabolic prospective than man made sugars or desserts. The main sugar in most fruits is fructose, but some other sugars are present in various proportions as well. Fructose from fruits metabolically behaves completely different than manmade concentrated fructose from corn syrup or other manmade sugars. It is chemically and mechanically bound to fibers and other fruit components and as a result it is released into the blood stream slowly without any sudden blood glucose spikes. The below fructose section explains why after eating even significant amount of fruits we often still feel hungry. Practically all scientists believe that eating whole fruits should not result in excessive consumption of fructose as it comprises a very small percentage of the whole fruit. Most fruits have low glycemic index and low glycemic load and do not produce spikes of insulin (fructose does not require insulin for metabolism), which partially explain why most fruit are weight gain friendly. Most fruits are also very high in water content, often as high as 90-95 %, and idigestible fibers which contributes to their satiety satisfying properties by share volume. Fruitarian diets are controversial despite the fact that fruits are considered to be very healthy.
Fructose.
Fructose comprises 50% of table sugar (the other 50% is glucose) and it is present even in higher concentrations in man-made fructose corn syrup. It is metabolised only by liver which transforms it into triglycerides (fat). Unlike other sugars it does not stimulate the production insulin (which is not necessarily bad), but also does not stimulate the production of Leptin, a hormone which inhibits hunger. Fructose does not inhibits hunger but increases cravings for food to which it is added. As a part of the added sugars It has been directly linked to the epidemic of obesity, diabetes etc. It is the most unhealthy part of most processed food. It is also a sugar used juices and sodas. The only way to avoid it is by avoiding any processed food.
Processed Fruits.
Fruits are healthy. Processed fruits are not healthy and they are not fruits. In my opinion freezing is the only weight management friendly way to preserve fruits. I do not like juices in general, with only exception being when you physically see the fruit being squeezed right in front of you. But even then, I think the liquid sugary part should be discarded and fibres and solid parts are to be consumed, this is a "good for you" part of the fruit, not a liquid high in fructose and sugars juice. Commercially processed fruits (juices, jams, marmalade) have unnaturally high concentration of fruit derived fructose, often along with added fructose corn syrup or table sugar.