Effects of Advice to Drink 8 Cups of Water per Day in Adolescents With Overweight or Obesity: A Randomized Clinical Trial.
Study Goal
The researchers aimed to determine whether advising adolescents with overweight or obesity to increase water intake to 8 cups per day, alongside a weight-reducing diet, would improve weight loss outcomes compared to a control group without such advice.
Results Summary
The study found that while the water group increased their water intake more than the control group, there was no significant difference in BMI z-score changes between the two groups after 6 months. Despite behavioral supports, few adolescents achieved the target water intake.
Population
38 adolescents (27 girls, 11 boys; mean age 14.9 years) with overweight or obesity who reported drinking ≤4 cups of water per day.
Effective Dosage
Advice to increase water intake to 8 cups per day (intervention group).
Duration
6 months.
Interactions
None mentioned.
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
advice and behavioral supports to consume 8 cups of water per day in the context of a weight-reducing diet | no change | body weight | adolescents with overweight or obesity | no significant change | did not affect | #1 |
advice and behavioral supports to increase water intake to 8 cups per day | increase | self-reported change in water intake at 6 months | adolescents with overweight or obesity | difference from baseline, 2.8 cups per day | greater | #2 |
standardized weight-loss diet without advice to increase water intake | increase | self-reported change in water intake at 6 months | adolescents with overweight or obesity | difference from baseline, 1.2 cups per day | change | #3 |
advice and behavioral supports to increase water intake to 8 cups per day | increase | self-reported change in water intake at 6 months | adolescents with overweight or obesity | 1.6 cups per day | difference between groups | #4 |
advice and behavioral supports to increase water intake to 8 cups per day | decrease | 6-month change in body mass index z score | adolescents with overweight or obesity | difference from baseline, -0.1 | change | #5 |
standardized weight-loss diet without advice to increase water intake | decrease | 6-month change in body mass index z score | adolescents with overweight or obesity | difference from baseline, -0.1 | change | #6 |
advice and behavioral supports to increase water intake to 8 cups per day | no change | 6-month change in body mass index z score | adolescents with overweight or obesity | difference between groups, -0.0 | did not differ | #7 |
IMPORTANCE: Health care professionals commonly recommend increased water consumption, typically to 8 cups per day, as part of a weight-reducing diet. However, this recommendation is based on limited evidence and virtually no experimental data from the pediatric population. OBJECTIVE: To compare 2 standardized weight-loss diets among adolescents with overweight or obesity, either with or without additional advice and behavioral support to increase habitual water intake to 8 cups per day. DESIGN, SETTING, AND PARTICIPANTS: A randomized clinical, parallel-group trial was conducted between February 2, 2011, and June 26, 2014, at Boston Children's Hospital, Boston, Massachusetts, among 38 adolescents with overweight or obesity who reported drinking 4 cups or less of water per day. INTERVENTIONS: All participants in both groups received similar weight-reducing interventions, differentiated by advice about water intake (the water group received advice to increase water intake to 8 cups per day; the control group did not receive such advice) but controlled for other dietary recommendations and treatment intensity. The interventions included dietary counseling, daily text messages, and a cookbook with health guides. To support adherence to 8 cups of water per day, the water group received well-defined messages about water through counseling and daily text messages, a water bottle, and a water pitcher with filters. MAIN OUTCOMES AND MEASURES: The primary outcome was 6-month change in body mass index z score. Data analyses followed the intention-to-treat principle. RESULTS: All 38 participants (27 girls and 11 boys; mean [SD] age, 14.9 [1.7] years) completed the study. Both groups reported drinking approximately 2 cups of water per day at baseline. Self-reported change in water intake at 6 months was greater in the water group (difference from baseline, 2.8 cups per day [95% CI, 1.8 to 3.8]; P < .001) compared with that in the control group (difference from baseline, 1.2 cups per day [95% CI, 0.2 to 2.2]; P = .02) (difference between groups, 1.6 cups per day [95% CI, 0.2 to 3.0 cups per day]; P = .03). The 6-month change in body mass index z score did not differ between the water group (difference from baseline, -0.1 [95% CI, -0.2 to -0.0]; P = .005) and the control group (difference from baseline, -0.1 [95% CI, -0.2 to -0.0]; P = .008) (difference between groups, -0.0 [95% CI, -0.1 to 0.1]; P = .88). CONCLUSIONS AND RELEVANCE: Advice and behavioral supports to consume 8 cups of water per day in the context of a weight-reducing diet did not affect body weight among adolescents with overweight or obesity. Despite intensive behavior supports, few adolescents achieved the target of 8 cups of water per day. 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. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01044134.