You've probably heard that fasting can be extremely effective for people who want to lose weight quickly - and it is, but it's not that simple.
New studies show that lots of people gain weight back after they finish fasting, and it often happens pretty quickly.
Let's find out more about why it happens.
Studying fasting results
The University of Illinois Chicago conducted research on water fasting, where people only drink water for several days.
This type of fasting may help with weight loss, but it's not clear how long the weight stays off.
The health benefits, like lower blood pressure and better cholesterol levels, tend to disappear soon after the fast ends.
However, there don't seem to be any serious bad effects for those who do water fasting or a similar kind where people eat very few calories each day.
More about the study
Info comes from a study led by Krista Varady, a professor who specializes in nutrition and kinesiology.
She suggests that it's okay to try fasting, but it's a lot of effort, and the good effects might not last long.
She strongly advises not doing these fasts for more than five days without a doctor's supervision.
Why the study happened in the first place
The study was inspired because people started asking Varady about water fasting, and she wanted to see what science had to say.
The research reviewed eight studies on water fasting or a closely supervised fasting called Buchinger fasting, which is popular in Europe and involves a tiny amount of juice and soup each day.
The results showed that fasting could lead to noticeable short-term weight loss, but the benefits for things like blood pressure and cholesterol disappeared quickly.
