While fruit juice may seem like a healthy beverage to consume, new research has determined that drinking it daily may be connected with increased weight gain.

Researchers discovered a link between the consumption of a daily serving of 100% fruit juice and weight gain in children, according to a study published in the JAMA Network. They also found a “significant positive association” between fruit juice intake and weight gain in adults.

The study was a systematic review and analysis of 42 studies. Seventeen of them involved children and 25 involved adults. Researchers hoped to synthesize available evidence on the consumption of 100% fruit juice, which has no added sugar, and body weight, since previous studies and trials on the association between the two have yielded mixed findings, according to the researchers.

In children, researchers found that drinking 100% fruit juice was associated with a small increase in body mass index — a calculation that takes into account weight and height — especially among kids under 11 years old. In adults, they found that 100% fruit juice was associated with weight gain in studies that did not account for the intake of calories, which may suggest that excess calories play a role in the association.

“Ultimately, these findings support public health guidance to limit the consumption of 100% fruit juice, especially in young children — to consume whole fruit rather than fruit juices,” Michelle Nguyen, lead author of the study, told Healthline. “We hope these findings will inform clinical practice guidelines and public health strategies to reduce overweight and obesity.”

Why might fruit juice contribute to weight gain?

One major factor for why fruit juice may contribute to weight gain is the high sugar content, according to Healthline. Also, it is high in calories, but drinking it does not usually make people feel full, meaning they may drink more than planned. That could eventually cause extra body fat and excess sugar in the blood, which can lead to several adverse health conditions, including diabetes, heart disease and obesity.

“One fundamental problem with juice is quantity; consuming fruit this way makes it so easy to overdose,” study coauthor Dr. Walter Willett told CNN. “For example, how often do we eat three oranges? Yet, a glass of OJ is about three oranges that can be consumed in a minute or two, and we can go back and have another, and that will add many calories and lead to a spike in blood glucose.”

Fruit in juice form also may not contain the same carbohydrates, protein and vitamins as whole fruits, which come in “packages of nutrients,” pediatric endocrinologist Dr. Tamara Hannon told CNN. Juice, on the other hand, contains little to no fiber, which also contributes to the fact that it does not make people feel as full as eating actual fruit.

What are some alternatives to drinking fruit juice?

Researchers say their findings are in line with guidelines by the American Academy of Pediatrics, which advises parents and guardians to avoid juice entirely for babies younger than 1. They also advise to limit juice intake to 4 ounces a day for children between 1-3 years old and 6 ounces a day for children ages 4-6. Everyone else should drink no more than 8 ounces of 100% fruit juice a day, according to Dietary Guidelines for Americans.

Juice should not be seen as a healthy way to quench thirst, experts say, but it doesn’t have to be cut out entirely. 

“The key way to look at fruit juice is a sweet treat, not a health food,” Dr. Nate Wood, physician at the Yale School of Medicine, told Healthline. “It’s not the same as eating a serving of whole fruit. Fruit juice is not essential for children in the same way that it’s not essential for adults. We’re certainly better off opting for whole fruit.”

If people are looking to get their juice fix, they should ensure it is 100% juice so there isn’t extra added sugar, Wood said. For people who like the fruity taste of juice, a healthier alternative is still, seltzer or mineral water with a splash of fruit juice, which would contain less sugar than a full serving of fruit juice.