This post will be able as welcome as a spiral ham at a bar-mitzvah.
Everybody loves fruit, right? It's sweet, it's tasty, and it's oh so good for you.
That's true to a point, but it's easy to get in trouble with fruit. The fruit we have now bears little resemblance to what our poop throwing ancestors were accustomed to. It's been bred to death to be sugary.
If you think about it, fruit is a contract between the plant and the consuming animal. I give you this tasty treat and you, in turn, spread my seeds around. From the plant's point of view they want to do the minimum. I'll make this fruit just tasty and nutritious enough to make it worth your while to eat it. This could just as well be another "Our Friends the Plants" post. The plants aren't giving you this fruit out of the kindness of their little woody hearts.
I have a wild berry bush that grows on my property. The berries are tiny and the seeds are large in comparison to the amount of food you get. They're quite tasty, but it's a lot of work just to get a tiny snack that's wouldn't fill up a large bird. It's nothing like the mutant domestic berries you would see in the store. You could never get yourself in trouble with the wild berries. You'd get tired of picking them (and there aren't that many to begin with) before you could cause yourself any sugar related harm.
The one thing that fruit has that is bad for you is fructose. This is known as "fruit sugar", but is found all over then place. White refined sugar is half glucose and half fructose. High-fructose corn syrup, which is in almost every processed food now, is 55% fructose.
As tasty as it is, fructose is a liver toxin. Your liver can process small amounts of it without trouble, but when you bomb it with high levels of fructose and glucose at the same time (like, for instance, drinking a large glass of apple juice) you really mess yourself up. Fructose blocks glucose metabolism in the liver. This is a problem because the liver is the major reservoir of glucose for your body. When your liver is stuck dealing with fructose, your body has to produce more insulin to lower your blood sugar than normal. This free glucose gets taken up by the muscles first. But if you sit on your butt all day then you won't have much glucose capacity in you muscle tissue because A. it's probably close to full already since you don't exercise, and B. you don't have much muscle tissue in the first place.
Guess where all that free glucose goes that can't be stored in muscle tissue? Into fat. Your fat has a practically infinite capacity to store energy. There are a lot of people storing a lot of energy these days.
Sugar, no matter where it comes from can be a bad thing.
This is not to say that fruit doesn't have any redeeming qualities; It does. Things like berries are loaded with anti-oxidants. Apples have fiber. Grapes are a source of iron. Fruit is tasty, and we crave variety in our diet. But if fruit becomes a staple in your diet you'll suffer for it.
Think of it this way. Fruit is a dessert. If you were to replace all your cakes and pastries with an after dinner piece of fruit your health would improve immensely. Infrequent, and small amounts of fruit are tolerated just fine. This is why I recommend a maximum of one piece of fresh fruit per day. There is no minimum, you can get by just fine without it by eating plenty of meat and vegetables.
Please make a note that I said "fresh fruit" - not dried fruit, not fruit juice. I suppose if you only at the equivalent of one piece of fruit as dried or juiced you'd be okay, but nobody I know does that. (Well, except me, but that's another blog post.) Does you know how much juice is in one orange? Let me tell you, it's not much. The main problem with processed fruits is that it abets fruit abuse.
Just to stick to what's seasonal and fresh and keep it to one piece per day and you'll get all the benefits of fruit without the downsides.