While you know that water should be your go-to drink, it’s amazing how many people still don’t drink enough throughout the day. Research shows even mild dehydration can take a serious toll on your mental and physical wellbeing. A study published last year found that as little as a 2 percent decrease in your body’s normal water volume could cause headaches, fatigue, and difficulty concentrating, reports The Journal of Nutrition. Research also shows that even a small amount of dehydration can decrease your performance during both aerobic and strength training workouts. You don’t need to be sweating away on a treadmill to experience that level of dehydration—working at your computer for about an hour without any breaks for water is enough to have that kind of effect.  When it comes to beverages, energy drinks, sports drinks, coffee, and soda get all the attention—but water still reigns supreme. “The two most common things people ask me about is how to have more energy and how to lose weight,” says Kate Geagan, R.D., author of Go Green, Get Lean. “Water can help you do both.” Here’s why you need to drink more water—and how to make it a habit. (Don’t drink water because it’s “boring”? Flavor your water naturally with this Sassy Water recipe!) Lose Weight With WaterYou may have heard that thirst can masquerade as hunger. Science has shown that it’s actually true. You see, the symptoms of both thirst and hunger—fatigue, irritability, and light-headedness—are often similar. But our drive to eat is often much stronger than our drive to drink, so we interpret these signs as “I need food,” the journal Physiology & Behavior reports.  More from Prevention: 7 Ways To Control Your Cravings There are many other ways staying hydrated can help keep your waistline in check, too. You’re well aware that sugary drinks contribute to weight gain—but it’s not just the calorie count that’s to blame. Most sodas today are still made with high-fructose corn syrup. “Unlike carbohydrates containing 100% glucose, such as the starch found in rice, potatoes, bread, and pasta, fructose doesn’t seem to trigger the hormones that help you regulate appetite and fat storage. So the body never gets the message to stop eating,” Peter Havel, PhD, a nutrition researcher at the University of California, Davis, told Prevention in the story The Case Against Soda.  You’re not off the hook if you drink diet, either. “Even artificially-sweetened drinks may lead to weight gain because they can trigger an insulin response, which causes your blood sugar to drop and makes you hungrier,” Geagan says. In a study from The University of Texas Health Science Center San Antonio, people who drank two or more diet sodas a day had five times the increase in waist circumference over a 10-year period compared to people who didn’t drink any diet soda.  The solution is simple: water. Drinking two eight-ounce glasses of water before each meal helped dieters shed 5 pounds more over the course of the year than those who didn’t increase their water intake, Virginia Tech researchers found. “It’s a small change with a big impact that can help prevent weight creep as you age,” Geagan says. One of the reasons those extra sips make a difference is because they increase the weight of your meal so you feel more full and eat less. (Easy, right? For more ways to lose weight without starving, check out these 50 Ways To Lose 10 Pounds.) Ditch The Sports DrinkIf you’re planning a tough workout, you may think a sports drink will help you power through it or improve your performance. The truth: A big bottle of H20 will most likely do the trick. “If your workout is under 60 minutes of continuous exercise, then water is just fine,” says Eric Rawson, Ph.D., professor of Exercise Science at Bloomsburg University in Pennsylvania and President of the American College of Sports Medicine (ACSM) Mid-Atlantic Chapter.  More from Prevention: What To Eat Before And After Your Workout “Even a modest level of dehydration can compromise your performance and make your workout feel harder,” he says. That’s because your blood consists primarily of water; when there’s not enough water your blood volume decreases and your heart has to work harder to circulate blood through your body.  Start getting your drink on way before you hit the gym. Down about 16 ounces of water 2 hours before your workout to make sure you’re fully hydrated. Have about half a cup of water 15 minutes before and then a good squirt of water every 15 minutes during exercise, Geagan suggests. If you’re regularly sipping water throughout the day, you’re probably good on workout hydration. Not sure? Take the pee test: “As a general guideline if your urine is the color of light lemonade it means you’re well hydrated,” Geagan says.  More from Prevention: 6 DIY Health Checks To Do Right Now The One Thing You Must Carry In Your PurseWhen it comes to staying hydrated, Geagan says, “If you see it you’ll sip it.” In other words, keeping a water bottle with you at all times will increase the likelihood that you’ll drink water throughout the day. Toss a small spill-proof water bottle in your bag to sip on the go (Geagan likes the 13-ounce Eddy Kids from Camelback), and keep a supersized bottle by your desk. Don’t rely on coffee in the morning, either. Although coffee provides some hydration, your body only absorbs about 60 percent of the water in a cup of Joe compared to 90 percent in a cup of water. Make a habit of switching from coffee to water by 10 a.m., Geagan stresses. As for the advice to drink eight 8-ounce glasses of water daily? It has some merit, but it’s more a guideline than a rule since so many different things—the temperature outside, your level of physical activity, the altitude, your weight, and more—can impact how much water you need.  If the taste (or, rather lack of taste) of water turns you off, try one of these 25 Flat Belly Diet Sassy Water Recipes for natural, healthy way to flavor your water. More from Prevention: The No-Squats Belly, Butt, And Thighs Workout