As far as weight loss fads go, drinking hot water to burn fat is one of the odder, yet simpler ones we've come across. While there is limited scientific research (almost none) on the direct effects of hot water on weight loss, many alternative health advocates believe that it can aid in shedding pounds. Although even with the science that they're using, there's more of an argument for eating ice cubes, than hot water. 

The logic behind the claim is that your body uses energy (or calories) to regulate it's temperature. This is why many survival enthusiasts will know that you can't use frozen snow as a water source and have to thaw it first. But, it takes more calories to raise our body temperature, than it does to lower it. [1] Although potentially if your body is already running hot, then hot water could burn a few extra calories.

The short answer is technically the temperature of the water could make a slight difference, but we're not talking much. There are however, some reasons as to why people have seen some weight loss from hot water, and ultimately that comes down to correlation rather than causation. What do we mean by that? It means that they were inadvertantly drinking more water, which can, in some cases help with weight loss.

Drinking Water and Your Metabolism

Staying hydrated is crucial for maintaining optimal bodily functions, including metabolism. Studies have shown that even mild dehydration can slow down metabolism and impair fat breakdown [2]. Drinking an adequate amount of water throughout the day can help keep your metabolism running efficiently and support weight loss efforts.

Hot Water and Appetite Suppression

Water can also help control appetite and prevent overeating. Drinking water before meals can create a sense of fullness, leading to reduced calorie intake. Additionally, thirst can sometimes be mistaken for hunger, and staying hydrated can help differentiate between the two sensations. [2] There is actually some evidence that teas can increase this effect, although there isn't much to suggest the temperature matters all too much, but there's definitely some anecdotal evidence it could be a factor for some people. [3]

Placebo and Hot Water Appetite

There is also some reasonable grounds that if you beleive hot water will make you feel less hungry then you will, the placebo effect on appetite suppression is reasonably well documented, and it doesn't seem likely that hot water would be an exception in this case. [4]

Temperature of Water and Weight Loss

Now, let's get onto how hot water specifically could effect things.

Effects of Hot Water on Metabolism

Some proponents of drinking hot water claim that it can boost metabolism and increase calorie burning. While there is limited scientific research on this specific claim, there is evidence to suggest that thermogenic effects of hot water may have a temporary impact on metabolism. Although as we've mentioned frozen water does have this effect. [5]

Thermogenesis and Calorie Burning

Thermogenesis refers to the production of heat in the body, which can increase calorie expenditure. It is believed that consuming hot water can slightly raise body temperature, leading to a slight increase in metabolic rate and calorie burning. However, it is important to note that the impact of hot water on metabolism is likely to be modest and short-lived.

Fat Breakdown and Utilization

Hot water is believed to help break down fat molecules and promote their utilization by the body. The warmth of hot water can stimulate the activity of enzymes involved in fat metabolism, potentially aiding in weight loss efforts. However, more research is needed to confirm these claims and understand the mechanisms involved. [6]

Improved Digestive Health

Drinking hot water can help stimulate the digestive system and promote healthy digestion. Warm fluids, including hot water, can increase blood flow to the stomach and improve the function of digestive enzymes. This can aid in the breakdown and absorption of nutrients from food.

Relieving Constipation

Chronic dehydration can lead to constipation, as the body absorbs most of the water from food and drinking. Drinking hot water can help prevent and relieve constipation by supporting regular bowel movements. The warmth of hot water can help relax the muscles of the digestive tract and promote smoother bowel movements. This can lead to people being a few pounds lighter immediately mistaking the laxative effect for a permenant weight loss. [7]

So, Does Drinking Hot Water Burn Fat?

No, not really. It could have a mild calorie burning effect vs normal water, but we're talking single digit figures, nothing that will make a difference. It could however lead to temporary weight loss through relieving constipation and improving bowel movements.

References

1 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6870536/

2 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7068562/

3 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3809630/

4 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10045637/

5 - https://pubmed.ncbi.nlm.nih.gov/16822824/

6 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4735055/

7 - https://pubmed.ncbi.nlm.nih.gov/27684632/