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How Many Calories Break a Fast?

Intermittent fasting means stopping food consumption for a specific period of time. After that duration is over, you can start eating according to the normal routine and then start fasting again after some time. Adjusting to the new fasting routine can prove to be difficult for you, especially if you have decided to fast for an extended period. In such difficult circumstances, you might wonder about the least amount of calories allowed during a fast that can help you get through the day.

There is no simple answer to this question, as there are numerous scenarios that need to be discussed before coming to a conclusion.

Typically, many fasters believe that eating about 50 calories during a fast does not nullify the purpose of fasting. However, it is an inaccurate belief because a fast is broken as soon as any calories are consumed. Whenever any calories enter your body, the burning of glucose starts for the generation of energy. It means that fat burning, the primary focus of intermittent fasting, is stopped.

In this detailed article, we will discuss all of the important information about breaking fast and acceptable calories. You will get to learn about the impact of supplements on a fast as well.

James Clear – an influential entrepreneur – is believed to be the first person that popularized this inaccurate theory that 50 calories do not break a fast. Eating any kind of calories will keep you from achieving the aim of fasting and reaping all of its benefits. However, it should also be mentioned that some types of fasting do allow you to eat some calories. If you are on a long fast, for example, of 16 days, then you can eat a meal of 500 calories or less during the 8 hours a day. This is called the 16:8 rule in intermittent fasting.

During a water fast, juice fast, or a dry fast, consuming any calories should be avoided as it will break your fast immediately by disturbing the metabolic reactions in your body. Research has shown that a large number of people are comfortable with eating 50 calories during a single fast. However, that same report states that eating even a small quantity of calories is enough to break your fast as fat burning is stopped, and the purpose of fasting remains unfulfilled.

Fasting and Supplements

It is also important to note the relationship between fasting and supplements. If you are not sure about whether the supplements will break your fast, we have listed down the list of supplements that can and cannot break your break.

Supplements that Do Not Break a Fast

Supplements that can Break a Fast

On the other hand, the following supplements will definitely break your fast:

  • Gummy vitamins
  • Protein powder
  • Sugary supplements
  • Amino acids


To conclude, we can say that eating even a single calorie can void your fast. It is highly suggested that you fast with extreme caution and finish your entire calorie intake to enjoy all of the benefits of fasting.