Introduction

It is often advised that drinking plenty of water can aid in weight loss. Some online recommendations even suggest consuming about a gallon (approximately 4.5 liters) of water daily. The claim is that water boosts calorie burning and reduces appetite, leading to weight loss.

Myth 1: Water Helps Burn Calories

A small study conducted on 14 young adults showed that consuming 500ml of water increased resting energy expenditure (the number of calories burned by the body before exercise) by around 24%. However, this effect lasted only for an hour and had a minimal impact, with an average adult burning only an additional 20 calories, equivalent to a quarter of a cookie, for every 500 ml of water consumed.

Another study with eight young adults found a slight increase of 4% in calories burned when drinking cold water from the fridge. This could be because the body expends more energy to warm the water to body temperature or due to the increased fluid volume that needs to be filtered by the kidneys. However, this effect also lasted for only about an hour.

It is worth noting that these studies were conducted exclusively on healthy young adults. Further research is needed to determine if similar effects occur in other groups, such as middle-aged and older individuals.

Myth 2: Water Reduces Appetite

The notion that drinking water before meals can reduce appetite seems plausible, as it would occupy space in the stomach, resulting in consuming less food. Several studies, particularly those conducted on middle-aged and older individuals, support this claim.

However, one study discovered that while middle-aged and older participants lost 2kg over a 12-week period when they drank water before meals, younger participants (ages 21 to 35) did not experience weight loss regardless of whether they drank water before meals or not. The absence of a “blind” study design in this research raises the possibility that participants may have modified their food intake based on their awareness of drinking water before eating. The reason for the lack of effect in younger participants remains unclear and requires further investigation.

Although water may have some impact on appetite suppression, it does not appear to lead to significant long-term weight loss.

Water Alone is Not Enough

Water alone is not effective in regulating appetite, as evidenced by the fact that prehistoric people would have starved if this were the case. While water can contribute to feelings of fullness, it is quickly expelled from the stomach due to its liquid form. Moreover, the shape of the stomach allows fluids to bypass semi-solid food in the lower part of the stomach, resulting in rapid expulsion of water. Therefore, even if consumed at the end of a meal, water may not enhance the feeling of satiety.

If the goal is to eat less for weight loss, simply drinking more water may not be the optimal solution. However, studies indicate that when water is combined with substances like fiber, soups, or vegetable sauces, it can slow down gastric emptying and prolong the feeling of fullness. Replacing high-calorie drinks such as sodas and alcohol with water can also help reduce daily calorie intake, facilitating weight loss.

This report was prepared by Duane Mellor, Head of Evidence-Based Medicine and Nutrition at Aston Medical School, Aston University.

Source: Science Alert