According to the US Centers for Disease Control and Prevention, more than one-third of US adults are obese. Obesity is defined as having a Body Mass Index (BMI) of 30 or higher. It can increase a person's risk of certain diseases such as heart disease, stroke, high cholesterol, high blood pressure, diabetes, and liver disease. Weight management strategies typically involves modifying diet and physical activity behaviors. The feeling of hunger can make some of these changes difficult.
Researchers from The Lancet Oncology England wanted to investigate the effectiveness of drinking water before meals as a weight loss strategy for adults with obesity. They hypothesized that the water would create a feeling of fullness that would reduce food consumption. The trial, published in Obesity, found that water preloading before main meals lead to weight loss.
The randomized trial included 84 adults with obesity. The participants were randomized to either a group that was asked to drink water before meals or a group that was asked to imagine their stomach was full before meals. The water group drank 2 cups (500 milileters) of water 30 minutes before main meals as well as additional water during the meals. Both groups received weight management consultations. Participants' weight was recorded at weeks 6 and 12.
At 12 weeks, the study found that participants in the water preloading group lost 2.8 pounds (1.3 kilograms) more than the group that imagined a full stomach. The difference was not as significant after accounting for other influential factors such as age and gender.
A randomized control trial is considered the most reliable form of research, but how the research is done will affect its reliability. This was a fairly small trial and lower number of participants means lower reliability in outcomes. The trial compared 2 treatments of unknown effectiveness instead of comparing them to a group with no intervention. As a result it is hard to tell if the results truely reflected the benefits of water preloading for weight loss or simply that preloading was better than imagery and neither were effective.
Cutting calories is an integral part of any weight loss plan. However, hunger can often lead to overeating and passing caloric intake recommendations. Drinking water before a meal may help create feeling of fullness or satiety during the meal which may help curb overeating. It may be a safe, easy way to help those who have a tendency to overeat. Consider working with a dietitian to help develop an effective weight loss plan.
Family Doctor—American Academy of Family Physicians
US Centers for Disease Control and Prevention
Parretti H, Aveyard P, et al. Efficacy of water preloading before main meals as a strategy for weight loss in primary care patients with obesity: RCT. Obesity (Silver Spring). 2015 Sep;23(9):1785-1791.
Overweight and obesity. Centers for Disease Control and Prevention website. Available at: . Updated September 3, 2014. Accessed December 9, 2014.
Last reviewed August 2015 by Michael Woods, MD