Researchers from Boston Children’s Hospital, Boston, MA, and St. Michael’s Hospital, Toronto, Ontario, Canada, report that consuming 8 cups of water daily in the context of a weight-loss diet did not affect body weight among overweight or obese adolescents. Full findings from the randomized, parallel-group clinical trial are published in JAMA Pediatrics.

The clinical recommendation to consume 8 cups of water daily as part of a weight-loss diet is “based on limited evidence and virtually no experimental data from the pediatric population,” described study author Julia M. W. Wong, PhD, RD. She and coauthors compared 2 weight-loss diets in adolescents who were overweight or obese, either with or without additional advice and behavioral support to increase regular water uptake to 8 cups daily. They conducted a clinical trial (n=38) between February 2, 2011 and June 26, 2014 among adolescents with overweight or obesity who reported drinking ≤4 cups of water daily. 

Study participants received similar weight-reduction interventions with varied advice about water intake: the water group was advised to increase intake to 8 cups daily whereas the control group did not receive advice. Both groups were controlled for other dietary recommendations and treatment intensity. Interventions included diet counseling, daily text messages, and a cookbook with health guides. For additional adherence support, the water group received well-defined messages about water through counseling, daily text messages, a water bottle, and a water pitcher with filters.  

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The primary outcome was the 6-month change in body mass index (BMI) z score. The data showed both groups drinking approximately 2 cups of water daily at baseline. At 6 months, the self-reported change in water consumption was higher in the water group (difference 2.8 cups daily, 95% CI: 1.8–3.8; P<0.001) vs the control group (difference 1.2 cups daily, 95% CI: 0.2–2.2; P=0.02). 

The change in BMI z score at 6 months did not differ between the water group (difference –0.1, 95% CI: –0.2–0.0; P=0.005) and the control group (difference –0.1, 95% CI: –0.2–0.0; P=0.008). 

Overall, only a few study participants reached the target of 8 cups of water daily. Dr. Wong added, “Environmental interventions to reduce barriers to water consumption at school may be necessary in future research of the feasibility and effectiveness to achieve the target of an intake of 8 cups of water per day in adolescents.”


  1. Wong JM, Ebbeling CB, Robinson L, et al. Effects of advice to drink 8 cups of water per day in adolescents with overweight or obesity: A randomized clinical trial. JAMA Pediatr. 6 March 2017. doi: 10.1001/jamapediatrics.2017.0012

This article originally appeared on MPR