Thirsty? New Study Links Good Hydration To Slimmer Waistlines : The Salt A new study finds people who are well-hydrated have lower body weights and lower odds of obesity. It adds evidence to the theory that drinking lots of water may help in weight management.

Thirsty? New Study Links Good Hydration To Slimmer Waistlines

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ROBERT SIEGEL, HOST:

A new study is pointing to the importance of good hydration. As NPR's Allison Aubrey reports, there is fresh evidence that drinking plenty of water may help you maintain a slimmer waistline.

ALLISON AUBREY, BYLINE: One thing that lots of dieters have heard is that staying well-hydrated can help you lose weight. Family Doctor Tammy Chang says this is something that a lot of her patients ask about.

TAMMY CHANG: One of the things that they always tell me is, you know, I saw online that there's a relationship between drinking water and weight loss. Actually, we don't know if that's true.

AUBREY: The evidence just isn't there, so Chang and her colleagues at the University of Michigan analyzed survey data from 9,000 people.

CHANG: We collected a data set of people who were adults - so 18 to 64 - and we tried to see who's hydrated and who's not?

AUBREY: They used the results of a urine test that gives an objective measure of hydration.

CHANG: And what we found was that people who were inadequately hydrated had an increased odds of being obese.

AUBREY: More specifically, the odds of being obese were 1.5 times higher for people who lacked proper hydration.

CHANG: That's a pretty big increase, and so the fact that hydration could have this effect is interesting and important.

AUBREY: Now, lots of factors determine a person's weight. It could be that people who stay well-hydrated have other habits, say, a healthy diet that keeps them slimmer. So the study does not prove that staying hydrated helps manage weight.

But Eric Rimm of the Harvard School of Public Health says it does fit with a few small studies that found dieters who drink water before a meal do better at weight loss, at least in the short term.

ERIC RIMM: Over several months, people who were drinking water before their meal lose more weight.

AUBREY: Maybe we feel less hungry after filling up on water. Now, there's no hard and fast rule on how much water you need to drink. A gardener working outside needs more than someone sitting in an air-conditioned office. Tammy Chang says she tells her patients to notice the color of their urine. If it's dark, you likely need to drink more.

CHANG: If your urine is light almost like the color of water then you're probably well-hydrated.

AUBREY: This may be particularly important for older people. Research shows people over 65 don't feel as thirsty as younger people, even when they're getting dehydrated. Allison Aubrey, NPR News.

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