Some experts believe that drinking fruit juice may lead to obesity in children, but a new review has found that juice in moderation does not cause excess weight gain in children under 18.

Researchers pooled data from eight prospective observational studies of the association between regular 100 percent fruit juice consumption and weight gain. The analysis, published in Pediatrics, includes 34,470 boys and girls under 18.

The studies used something called the B.M.I. z score, which statistically adjusts body mass index according to age. Changes in these scores of 0.25 to 0.50 are generally considered to put the child at risk for obesity.

After controlling for total energy intake, birth weight, ethnicity and other factors, a 6- to 8-ounce daily serving of 100 percent fruit juice was associated with a 0.087 unit average increase in B.M.I. z score in children 1 to 6 — equivalent to about 0.3 pounds. In those 7 to 18, there was no link at all between drinking fruit juice and weight gain.

The lead author, Dr. Brandon J. Auerbach, an acting instructor in medicine at the University of Washington, said that based on the current evidence, “consuming one daily serving of fruit juice is not associated with weight gain in children. So fruit juice in moderation, not more than a serving a day, is safe.”