Does Dehydration Cause Weight Gain?

Feeling parched may be playing a part in your weight gain without you even realizing it.

Over half of all Americans have expressed a desire to lose weight, according to a recent Gallup poll. And according to the Centers for Disease Control and Prevention, more Americans are some version of a weight-loss diet compared to a decade ago, with the majority of dieters being over the age of 40.

From jumping on the intermittent fasting train to cutting out nearly all carbs, a la the keto diet, to following in Chris Pratt's footsteps and trying the Daniel Fast, there are many diets that are touted to support weight-loss goals. But while we may tweak our dietary habits in various ways to lose weight, several lifestyle factors such as our hydration status can also impact our weight-loss success in the long run. Which may lead people to wonder, does dehydration cause weight gain?

a collage featuring a photo of a woman drinking water with a background of a cracked surface
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How Hydration Affects Weight Status

There are many reasons a person may want to lose weight. They may have been advised by their health care team that it will help improve their condition, they may desire specific positive health outcomes, or they may want to feel more energized and confident. Many of us understand that consuming excess calories, leading a sedentary lifestyle and not getting quality sleep likely won't result in scale numbers moving in a desired direction. However, it might be less obvious how dehydration impacts healthy weight maintenance and achieving personal goals.

So, how does hydration impact weight loss? Fluid status can play a role in how our body is able to manage weight in a few ways.

The first factor is quite simple to understand. When people are properly hydrated, they don't feel thirsty. For some people, that thirst sensation may trigger a desire to eat (regardless of whether a person is truly hungry), which can make it more difficult to follow your hunger and fullness cues. In fact, there is evidence to suggest that increased water intake is associated with decreased food intake, and thus, lower overall calorie intake in certain populations. That is not to say that water is a replacement for a meal when you're hungry (it's not), but staying hydrated can help you eat more mindfully and more in-line with your body's needs.

The second factor is a bit more scientific in nature. Some data suggests that increased water intake drives thermogenesis, meaning that the body may produce more heat, and thus burn more calories. This effect can lead to a decrease in weight gain over time.

Finally, evidence exists suggesting a link between hydration status and the body's ability to break down fat, also known as lipolysis. Specifically, being adequately hydrated appears to support the natural process of breaking down fat, and being in a state of dehydration has the opposite effect.

Does Hydration Impact Weight Gain?

There are many factors that come into play when a person is trying to lose weight. While our eating pattern can be one part of the puzzle, it is important to keep in mind that other factors like our genetics, our lifestyle and any underlying medical conditions can impact our body's ability to lose weight as well.

In certain cases, it does appear that being properly hydrated may be one dietary goal that may help combat weight gain.

While most available data evaluating this relationship is observational in nature, some evidence shows that people who drink more water appear to have more weight-loss success. In some cases, this effect is observed more profoundly when caloric beverages are replaced by water.

According to results of a 2016 study in the Annals of Family Medicine using a nationally representative sample of over 9,000 subjects, adults who were inadequately hydrated had higher BMIs and higher odds of being considered obese compared with more hydrated adults. These conclusions were made even after controlling for confounding variables.

It is important to keep in mind that maintaining proper hydration won't be a magic bullet for weight loss for everyone, and there is some data suggesting that hydration status has no effect on a person's weight. But considering how proper hydration can play a positive role in so many aspects of our health, like temperature regulation, healthy heart function and well-lubricated joints, aiming to stay more hydrated comes with little downside. However, there are some cases where you may want to restrict your fluid intake, such as if you have an underlying condition like kidney disease. Always be sure to talk to your health care team before making a significant lifestyle change.

The Bottom Line

Maintaining proper hydration may help people avoid weight gain, based on the medical literature. But until we have more well-designed clinical trials that are not predominantly observational in nature, we can lean on the fact that maintaining proper hydration is linked to other positive health effects like helping our bodies process waste, protecting kidney function and lowering blood pressure. And if you happen to not gain more weight (if you are trying to avoid that) thanks to your stellar hydration status? Well, that is simply icing on the cake.

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