It's time to clear up some confusion about fruit, sugar, fructose and how this all fits together into a healthy diet.
Is the Sugar in Fruit Converted to Fat?
It is not true that all fructose is converted directly to fat in the liver. Some of it is converted into glycogen, a stored form of energy used to power your cells and muscles between meals, when your blood sugar is lower. As with all other nutrients, the amount of energy that is stored as fat depends on how much total energy you’re taking in vs. how much you’re using up. If you’re relatively active, a lot of the fructose you take in will be used to replenish liver glycogen stores. If you are taking in a lot more calories than you are burning, they’re going to get stored as fat. But in the big picture, it really doesn’t matter all that much whether those excess calories are coming in the form of glucose, fructose, starches, or fats.
Can Too Much Fruit Hurt Your Liver?
It is also true that overwhelming the liver with huge amounts of pure fructose—as in some of the studies that are frequently cited to stoke up anti-fructose hysteria—can create big problems, including liver damage. But you are unlikely to be getting huge amounts of pure fructose from eating two or three servings of whole fruit each day—even if you are taking your life into your hands by eating bananas.
One of my favorite ways to eat bananas these days is frozen and blended in my food processor with a teaspoon or two of unsweetened cocoa powder into a frozen yogurt like consistency. If you’ve never tried this, you might be amazed just how delicious and satisfying a dessert this makes—and all for about 100 calories and zero added sugar or artificial sweeteners. If that’s one of the “worst” fruits you can choose, I’d say that we probably have better things to worry about.
The Bottom Line on Fruit and Fructose
Diets that are very high in sugar are a problem—for a number of reasons. Eating large amounts of sugar will flood the body with both glucose and fructose—and each of these are problematic in their own way. Too much glucose eventually impairs blood sugar metabolism. Too much fructose eventually harms the liver. Taking in a lot of sugar can also lead to taking in too many calories, and this always leads to weight gain and fat storage.
But, as they say, the dose makes the poison. Something that may be harmful in high amounts may be harmless—or even beneficial—in small amounts. And in the context of an otherwise healthy and calorie-appropriate diet, the amount of sugar, glucose, and fructose that you will get from a couple of servings of fruit is not going to give you diabetes, liver damage, or turn your body into a fat storage factory—no matter which type of fruit you choose to enjoy.