Does drinking water affect your weight?

Does drinking water affect your weight? Yes, but not in the way most people think. Water alone won’t melt fat off your body, and no amount of “water hacks” will replace a good diet and exercise. But research shows that drinking more water can help you lose weight when you use it the right way.

A 2019 systematic review looked at six clinical trials on water and weight loss. Every single study showed weight loss after following up for at least 12 weeks. People lost anywhere from 0.4 kg to 8.8 kg, with an average weight loss of 5.15%. The biggest results came from replacing sugary drinks with water.

Does Drinking Water Before Meals Help You Eat Less?

Drinking water before meals helps you eat less food. When you drink water before eating, your stomach fills up and sends signals to your brain that you’re getting full.

In one study, middle aged and older adults who drank two cups of water before meals ate 60 to 75 fewer calories per meal. Over 12 weeks, the water drinking group lost 44% more weight than the group that didn’t drink water before meals. That worked out to about 2 kg more weight lost.

A Korean study found that people who drank water before a test meal ate 123g of food compared to 162g when they didn’t drink water beforehand. They still felt just as satisfied after eating less.

This trick works best for people over 40. Research shows younger adults don’t eat less when they drink water before meals, but older adults do. Scientists think this happens because the stomach becomes more sensitive to stretching as we age.

How Much Water Burns Calories?

Drinking water burns a small number of extra calories through something called thermogenesis. Your body uses energy to process the water you drink.

One study found that drinking 500ml of water increased metabolic rate by 30% for about an hour. The researchers calculated that drinking 2 litres of water per day would burn roughly 96 extra calories.

Cold water burns slightly more calories because your body has to warm it up to body temperature. But we’re talking about 8 extra calories per glass compared to room temperature water. That’s basically nothing.

Here’s the honest truth. The calorie burning effect of water is too small to cause real weight loss on its own. If you drink 8 glasses of ice cold water per day, you might burn an extra 56 calories. That’s the same as walking for 10 minutes.

More recent research has questioned whether water causes any meaningful thermogenic effect at all. A study in the Journal of Clinical Endocrinology & Metabolism found that drinking room temperature water did not increase energy expenditure at all. The science here is mixed, so don’t count on water to rev up your metabolism.

Does Drinking Water Replace Sugary Drinks?

Replacing soft drinks, juice and other sugary beverages with water is one of the best things you can do for weight loss. This works because you’re cutting calories, not because water has any special fat burning properties.

A single can of soft drink contains about 140 calories and 39 grams of sugar. If you drink one soft drink per day and switch to water, you’ll cut nearly 1000 calories per week without changing anything else.

Research published in longitudinal cohort studies found that replacing one serving per day of a sugar sweetened beverage with 240ml of water led to 0.49 kg less weight gain over four years.

The American diet gets about 17% of total daily calories from beverages. Most of these come from soft drinks, energy drinks, fruit drinks and alcohol. Switching these to water makes a real difference.

How Much Water Should You Drink For Weight Loss?

Most health organisations recommend about 8 glasses or 2 litres of water per day. But the right amount depends on your body weight, activity level and climate.

A good rule of thumb is to drink half your body weight in ounces. If you weigh 80kg (176 pounds), that works out to about 88 ounces or 2.6 litres per day. If you exercise or live in a hot climate, add more.

For weight loss specifically, here’s what the research supports.

1. Drink 500ml (2 cups) of water 30 minutes before each main meal
2. Drink water instead of soft drinks, juice and other caloric beverages
3. Aim for at least 2 to 3 litres of total water intake per day
4. Spread your water intake throughout the day rather than drinking it all at once

One study had overweight women drink 1.5 litres of water above their normal intake for 8 weeks. They drank 500ml before breakfast, lunch and dinner. At the end of the study, they had lower body weight, lower BMI and reduced appetite.

Does Dehydration Make You Gain Weight?

Being dehydrated can cause you to eat more food. Your brain sometimes confuses thirst signals for hunger signals, especially as you get older. When you feel hungry, you might actually be thirsty.

Research shows that habitual water drinkers consume about 9% fewer calories per day, roughly 194 calories less, compared to people who don’t drink much water. Part of this comes from avoiding unnecessary snacking.

Staying hydrated also helps your body break down fat more effectively. A process called lipolysis, where fat molecules get broken down for energy, requires water. When you’re dehydrated, this process slows down.

Dehydration also tanks your energy levels. Even mild dehydration of just 2% body weight loss reduces exercise performance, cognitive function and motivation. This makes it harder to stick with workouts and healthy eating habits.

What’s The Best Time To Drink Water For Weight Loss?

The best time to drink water for weight loss is 30 minutes before meals. This is the timing that research supports.

1. First thing in the morning to rehydrate after sleep
2. 30 minutes before breakfast
3. 30 minutes before lunch
4. 30 minutes before dinner
5. During and after exercise

Avoid drinking large amounts of water right before bed. This disrupts sleep with bathroom trips, and poor sleep is linked to weight gain.

Does Water Temperature Matter?

Cold water burns slightly more calories than warm water, but the difference is tiny. Drinking 500ml of ice cold water might burn about 15 to 20 extra calories compared to room temperature water.

However, warm water may have its own benefits. One 2023 study found that people who drank 200 to 250ml of warm water after each meal lost more weight than people who didn’t.

Pick whichever temperature you prefer and will actually drink. Consistency matters more than temperature.

FAQ

How much weight can you lose by drinking water?

Research shows people can lose 0.4 to 8.8 kg by increasing water intake, with an average of about 5% body weight. The most weight loss comes from replacing caloric drinks with water and drinking water before meals. Water alone won’t cause large weight loss without other changes.

Should I drink water even if I’m not thirsty?

Yes. Thirst is not always a reliable indicator of hydration, especially as you get older. By the time you feel thirsty, you may already be mildly dehydrated. Set reminders to drink water throughout the day.

Can you drink too much water?

Yes. Drinking excessive amounts of water, especially during intense exercise, can dilute sodium levels in your blood. This condition called hyponatremia is rare but serious. Stick to the recommended 2 to 3 litres per day for most people.

Does sparkling water work the same as still water?

Yes. Sparkling water hydrates you just as well as still water. It has no calories and can help fill your stomach before meals. Just avoid sparkling waters with added sugars or sweeteners.

Will drinking water help me lose belly fat specifically?

No. You cannot spot reduce fat from any area of your body. When you lose weight, you lose it from your whole body. Drinking water supports overall weight loss, not targeted fat loss.

How long does it take to see results from drinking more water?

Most studies show measurable weight loss benefits after 8 to 12 weeks of increased water intake. You may notice reduced appetite and better energy levels within the first few days.

Is cold water or warm water better for weight loss?

Both work about the same. Cold water burns a few extra calories as your body warms it up, but the difference is too small to matter. Warm water before meals may help with digestion. Choose whichever you’ll drink more consistently.

What if I don’t like plain water?

Add lemon, lime, cucumber or fresh mint to your water. You can also drink sparkling water, herbal tea or other unsweetened beverages. Avoid adding sugar, honey or artificial sweeteners.