Weight Loss: 5 Ways Hydrating Helps You Shed Pounds

If you’re dehydrated, both your workouts and your results (ahem, fat loss) will suffer. Unfortunately, you don’t start to feel thirsty until you lose about 2% of your body weight in water. This is actually the same point at which your exercise performance takes a nosedive, according to research published in the American Journal of Clinical Nutrition.

While the American Council on Exercise recommends that active women drink 2.7 liters (91 ounces) of water per day, Kaufman recommends drinking 16 of those ounces before hitting the gym and another 8 ounces every 30 minutes during your sweat session. That’s way more than eight glasses per day!

To make sure that you’re totally fueled up on H2O, weigh yourself before and after your workout (just pee before stepping on the scale), says Florida-based dietitian Jaime Mass, RD. If your post-workout weight is 2% or more less than your pre-workout weight (for example, 150 pounds before, 147 pounds after), you aren’t drinking enough. Kick up your hydration even further.

Sweat sessions aside, water boosts your calorie burn—period. That’s because every time you eat or drink, your body has to work (aka burn calories) to process whatever’s coming in. It’s called “diet-induced thermogenesis,” and it works for water pretty much the same way it works for anything that contains calories.

In one study of healthy men and women, published in the Journal of Endocrinology & Metabolism, drinking about 16 ounces of water temporarily spiked participants’ metabolic rate by 30%. The researchers concluded that increasing water intake by 1.5 liters (about six 8 ounce glasses) per day would increase daily calorie burn by about 200 calories.

It helps you heed hunger cues.

You’ve probably heard the whole “water makes you feel full” spiel before. But water’s ability to help you pinpoint your hunger level is even more helpful than its filling abilities. Oftentimes, we think that we’re hungry, but we’re really just thirsty, says Mass. For instance, many of the feelings associated with being hungry, such as a gurgling stomach, low energy levels, and even light-headedness, also strike when you’re running low on water.

When you feel “hunger” set in, drinking some water can help you determine how ravenous you actually are. One 2015 studyfrom the University of Oxford found that obese adults who drank about 16 ounces of water 30 minutes before their meals ended up eating fewer calories and losing 2.6 more pounds than those who simply imagined that their stomachs were full before sitting down for their meals. Kaufman has her patients follow the same 16-ounces-before-mealtime tactic.

It boosts energy.

Energy and weight loss are two peas in a super-svelte pod. When your energy levels are up, you crush workouts, have fewer cravings, and are generally way more likely get your butt off of the couch. That’s where water—which makes up nearly 70% of the human body—comes in. It keeps your cells firing, your muscles fed with oxygen and nutrients, and your brain focused on working toward those weight loss goals, says Kaufman.

Drudging your way through a 3 PM slump? Instead of running to the vending machine for a sugar fix, try drinking some water. Dehydration loves to masquerade as fatigue.

It keeps you from drinking other things.

As great as water is on its own, it’s even better when you compare it to other bevs, like soda and heavily whipped coffee drinks (though we love a frap as much as the next person). Luckily, a 2015 BMC Public Health study of more than 1,100 adults found that every 3.4 ounces of plain water consumption results in a 0.7 ounce reduction in caloric beverages. More water and less soda? Check.