Breath

One common, though often surprising, side effect of water fasting is a noticeable change in breath smell. While this can be uncomfortable, it’s a natural part of the fasting process. This change in breath, commonly described as metallic or foul, is often due to the body entering ketosis—a state where it burns stored fat for fuel. When the liver breaks down fats, it produces ketones, including acetone, which can give breath a distinct, sometimes unpleasant odor. In fasting, this is actually a positive sign that the body is shifting into fat-burning mode, as highlighted by experts like Dr. Jason Fung.

However, fasting breath can also be caused by a reduction in saliva production. As we fast, our mouths become drier, and saliva, which normally helps cleanse the mouth of bacteria, decreases. This dryness, combined with the release of ketones, contributes to the stronger breath odor many experience.

So, should you control it? Trying to manage fasting breath is generally safe, but it's important to avoid solutions that could disrupt the fast, such as sugary gums or mints. Instead, opt for safe alternatives like drinking more water, which can help flush out ketones and keep your mouth moist. Herbal teas (unsweetened and caffeine-free) can also offer temporary relief without breaking the fast. Some fasters find that rinsing their mouth with water or a saltwater solution can help, as can brushing their teeth more frequently.

Ultimately, while fasting breath may not be pleasant, it’s a normal part of the process and a sign that your body is doing the work of burning fat. Remember, this is temporary, and once you transition back to regular eating, your breath will improve.