The idea behind drinking cold water for weight loss is a thermogenic reaction — that your body expends extra energy, aka extra calories, to compensate for the temperature difference between your body and the water. However, the science behind this is inconclusive and sometimes controversial.
The science behind drinking cold water for weight loss isn't yet conclusive, but a couple of studies indicate that cold water might provide a small but measurable boost to your weight loss efforts.
Drinking Water for Weight Loss
One notable study about whether drinking extra water can aid weight loss was published in the September 2013 issue of the Journal of Clinical and Diagnostic Research. The study involved 50 subjects who were asked to drink 500 milliliters (just under 17 ounces) of water a half-hour before breakfast, lunch and dinner, on top of their normal daily water intake.
At the end of an 8-week period, researchers found that the extra water intake produced statistically significant changes in body weight and body composition. However, the mechanism behind that weight loss isn't entirely clear. In particular, the researchers note that water is a natural appetite suppressant, and it's unclear whether the extra water intake before meals affected the subjects' overall calorie intake.
Moreover, some other studies conflict with those results. For example, in the December 2015 issue of Nutrition and Diabetes, researchers published the results of an even smaller study (involving 27 subjects) that evaluated whether drinking 500 ml of water produced a statistically significant difference in weight control.
They concluded that the water intake didn't produce any statistically significant difference. However, their study was based only on a single intake of water versus eight weeks in the aforementioned study, so it's impossible to say they disproved any cumulative effects of increased water intake for weight loss. And neither of the two studies discussed took water temperature into account.
Another study, published in a 2018 issue of Frontiers in Physiology, involved 23 subjects who were asked to drink either hot or cold caffeinated herbal tea. Their results showed that the cold tea produced more thermogenesis and fat oxidation than drinking hot liquids — suggesting that it might be more effective to drink cold water for weight loss over room- or body-temperature water, although more research is needed to establish conclusive results.
Read more: Easiest Way to Lose Water Weight
Dangers of Drinking Cold Water
If drinking water is good for you, can you have too much of a good thing? Yes, there are some dangers of drinking too much cold water. As Harvard Health Publishing notes, water serves many important purposes in your body, including normalizing blood pressure and heartbeat and cushioning your joints; the researchers in the Journal of Clinical and Diagnostic Research study note that even mild dehydration can inhibit fat oxidation, which is necessary for weight loss.
There are no documented, objective dangers to drinking cold water. However, if you go too far overboard with drinking water to lose weight fast, regardless of the water's temperature, you run the risk of developing hyponatremia, or low blood sodium, as a result of being over-hydrated. Harvard Health Publishing offers a general guideline of drinking 4 to 6 cups (32 to 48 ounces) of water per day, or more if you're exercising or outside in hot temperatures.
But you might need less water if you have certain medical conditions — including thyroid disease or kidney, liver or heart problems — or if you take certain medications that cause water retention. When in doubt, it's best to talk to a doctor about how much water you should be taking in.
- Harvard Health Publishing: "How Much Water Should You Drink?"
- MedlinePlus: "Low Blood Sodium"
- Frontiers in Physiology: "Cardiovascular and Metabolic Responses to the Ingestion of Caffeinated Herbal Tea: Drink It Hot or Cold?"
- Nutrition and Diabetes: "Water-Induced Thermogenesis and Fat Oxidation: A Reassessment"
- Journal of Clinical and Diagnostic Research: "Effect of ‘Water Induced Thermogenesis’ on Body Weight, Body Mass Index and Body Composition of Overweight Subjects"