Whole fruits are rich in vitamins, minerals, and bioactive compounds that promote health. They also contain essential fiber, which supports digestion and regulates blood sugar levels. Fruit juices, on the other hand, contain little fiber, are high in natural sugars, and can cause rapid blood sugar spikes, impairing metabolism. A recent systematic review and meta-analysis found that consuming 100 percent fruit juice promotes weight gain in children.

Researchers analyzed the findings of 42 randomized clinical trials investigating the effects of consuming 100 percent fruit juice on body weight. The various trials included more than 45,000 children and 268,000 adults.

They found that for every additional serving of juice (defined as 8 ounces) per day, the children showed a modest increase in body mass index, a proxy for body fatness. However, the findings in adults were mixed, with studies that didn’t adjust for caloric intake observing greater body weight gain than those that didn’t.

These findings suggest that a single serving of 100 percent fruit juice daily promotes weight gain in children – a noteworthy finding considering that roughly half of children and teens in the U.S. consume at least one serving of fruit juice a day. An 8-ounce serving of 100 percent orange juice contains about 110 calories and 20 grams of sugar, while a medium-sized whole orange contains approximately 62 calories and 12 grams of sugar. Encouraging the consumption of whole fruits versus fruit juices may influence body weight in children.