Short Answer
No need to avoid fruit. It is perfectly healthy, however, moderation is key. In general I recommend up to about 3 servings/day.
Long Answer
Fruit does have natural sugars, but it also has fiber, antioxidants, and vitamins to go along with it -- all things that are really good for us.
We can, however, get too much sugar.
Sugar that’s found in food is usually made of a mix of glucose and fructose, two single sugar molecules (read more here). This is true for table sugar (sucrose), whole fruit, fruit juice, corn syrup, honey, etc.
For example:
Sucrose = Glucose + Fructose (50/50)
Fruit = Glucose + Fructose + Sucrose + Fiber
Fruit Juice = Glucose + Fructose
Corn syrup = Glucose + Fructose (45/55)
Honey = Glucose + Fructose (60/40)
The issue with sugar actually lies more with fructose, as fructose gets converted to glucose by the liver, whereas glucose directly fuels our muscles, brain, and other bodily functions. A small amount of fructose is perfectly fine, but we run into issues with too much (1). Too much fructose overloads the liver and can end up turning into fats, resulting in a non-alcoholic fatty liver. A fatty liver is associated with insulin resistance.
It is somewhat difficult to get too much fructose from whole fruit because it has fiber, which 1) slows down the absorption of sugar from the fruit into our bodies, and 2) makes us feel full so we are less likely to overeat it (Think: Eating as many apples as possible vs. drinking as much apple juice as possible). Plus, the fiber and vitamins that come from whole fruit have a host of other benefits.
The trouble with foods containing purely sugar like table sugar, fruit juice, corn syrup, honey, etc. is that they are incredibly easy for the body digest (requires little breakdown) and to over-consume. Would you agree that it's relatively easier to drink a glass of orange juice, containing about 28g of sugar, than it is to eat an orange, containing about 12g of sugar?
How much fructose is too much? In general, over 25g of fructose, which is the amount you get in roughly 3 servings of whole fruit (1).
There are, however, some people who will likely tolerate more fructose without adverse reactions. For example, athletes generally need more carbohydrates and will likely get them from a variety of sources, fruit included. They participate in higher amounts of activity and are, therefore, using up their carbohydrate stores in the liver and muscles more rapidly and/or using the sugar immediately for energy. So, even though they may take in more sugar, they are not necessarily overloading their liver with fructose.
The amount of fructose we get from a serving of fruit does also depend on the type of fruit. For example, an apple has about 12g of fructose, whereas a serving of blueberries has about 7-8g (2).
For more information, check out the nutritional profile of various fruits on whfoods.org, and read these other sources of information on fruit:
Why Fruit is a Good Source of Carbohydrates by The Paleo Mom
Why Fear of Fruit is Fruitless By Laura Schoenfeld, RD
Conclusion
Don’t avoid fruit, but don’t over do it and become a fruititarian, either. When it comes to desserts and other forms of added sugars, enjoy in moderation.
Sources
1. Briden, Lara. The Period Repair Manual, 2nd ed. Greenpeak Publishing; 2018
2. The World's Healthiest Foods. http://whfoods.org/genpage.php?tname=foodspice&dbid=8.
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