Drinking a glass or more of 100% fruit juice each day was linked to a small increase in weight in children and adults, according to a new analysis of prior studies.

“One fundamental problem with juice is quantity; consuming fruit this way makes it so easy to overdose,” said coauthor and leading nutrition researcher Dr. Walter Willett, a professor of epidemiology and nutrition at Harvard T.H. Chan School of Public Health and professor of medicine at Harvard Medical School in Boston.

“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,” Willett said in an email.

Over time, too much sugar in the blood can lead to insulin resistance, metabolic syndrome, diabetes, heart disease, obesity and other chronic conditions, experts say.