Health experts say to drink eight glasses of water a day, and now there is one more reason to follow that advice. Researchers have shown that keeping hydrated is associated with lower weight, with poor hydration linked to higher risk of obesity.
The research comes from Tammy Chang, MD at the University of Michigan, along with other researchers. The study authors published their results in the July/August issue of the journal Annals of Family Medicine. Although doctors often suggest drinking water to help reduce weight gain, the researchers have analyzed the link between poor hydration and obesity.
For their study, the researchers studied data from the National Health and Nutrition Examination Survey (NHANES) from 2009 to 2012. The 9,528 study participants were between 18 and 64 years old and represented a sample from across the country. In particular, the researchers looked at data for body mass index (BMI), with those above 30 BMI categorized as obese and those under 30 BMI counted as not obese. The researchers also looked at the concentration of chemicals in urine, with osmolality values greater than 800 mOsm/kg counted as not hydrated. Experts consider osmolality a better measure of hydration than water intake because it reflects the balance between water and chemicals in the body. The researchers adjusted their data for factors such as age, sex, ethnicity, and poverty.
When the researchers analyzed their data, they found that 32.6 percent of the participants were inadequately hydrated. These poorly hydrated study participants were more likely to have high BMIs than the participants who were fully hydrated, at about 1.32 kg/m2 higher BMI. The inadequately hydrated participants faced a 1.59 times higher chance of being obese as well. This suggests a link between staying hydrated and keeping weight in check, although further studies would need to confirm that staying hydrated can curb obesity.
The study authors point out that as someone’s BMI increases, they need more fluids to keep hydrated, since the body’s water requirement depends on body weight, surface area, and metabolic rate. Doctors may not be giving their patients advice to increase their water intake as their weight rises, although this is important for health. Those who are obese may also be eating higher-calorie foods, which tend to be foods with a lower water content than lower-calorie foods such as fruits and vegetables.
Other researchers have used brain scans to analyze how drinking water affects the desire to eat. It seems that as people drink water, it can contribute to their feelings of fullness. As they feel more full, they will be less likely to eat more calories, keeping their weight down.
The authors of the current study point out just how essential keeping hydrated is for health. Poor hydration is linked to poorer mental, emotional, and physical health. This can have an effect on someone’s performance when they have to use their attention, memory, and motor skills for different tasks. Other researchers have linked poor hydration to headaches, poor mood, and poor kidney function, further emphasizing just how essential it is for everyone to keep hydrated.
There are two main takeaways from the current study. On the one hand, the findings emphasize how common poor hydration is, at about a third of the population, despite how important hydration is for health. On the other hand, the study emphasizes how important it is for doctors to look at their patient’s BMI when giving advice for keeping hydrated. Although the eight glasses of water a day may be good general advice for most people to aim for, people in different situations, such as obese individuals, may need even more water to stay healthy.
There are a few things people can do to keep themselves hydrated. Although water, at zero calories, may be the best beverage to consume to keep hydrated, other liquids such as juice can also help improve hydration. If someone is exercising or out in the sun, they can become dehydrated, and should ensure they drink plenty of fluids before, during, and after their activities. It may be best to avoid alcohol and drinks with caffeine, such as tea and coffee, which can have a drying effect and, in the case of alcohol, plenty of empty calories. Eating foods high in water content can also help promote hydration, with the added bonus of fruit and vegetables being high in nutrients.