Many people intentionally fast for reasons ranging from weight loss to religion. If people avoid eating food for an entire day, how would it affect their mood or their cravings for certain foods or the amount of food eaten after the fast? Researchers from Spain examined this question and compared responses between women with bulimia and women without an eating disorder.
The study, soon to be published in the European Eating Disorders Review, examined 21 women with bulimia and 20 women who didn’t meet criteria for any eating disorder. After eating a normal size lunch (typically the largest meal of the day in Spain), the women were asked to avoid eating or drinking anything except water for 20 hours. The next morning, they were provided with a large buffet-style breakfast. To make sure everyone actually followed through with fasting instructions, the researchers took blood samples before/during/after the fast and told the women in advance about the purpose of blood samples.
All the women said they craved food more strongly as a result of the fasting. The more intensely they reported craving food, the more calories they consumed at the breakfast buffet. There also weren’t any differences in terms of the types of foods (e.g. proteins, carbs, fats) that healthy women ate compared to women with bulimia.
Given that everyone ate similar amounts and types of foods, this suggests that fasting does not typically lead to binge eating as some might have guessed. On the other hand, the women ate the breakfast buffet together which begs the question – would they have consumed more food if they ate alone?
The main difference between the two groups of women had to do with how fasting affected their mood. Healthy women reported a decrease in their negative mood 6 hours into the fast, but then reported an increase in negative mood at the 20 hour mark that was over and above their original report. On the other hand, women with bulimia reported that their negative mood decreased 6 hours into the fast and continued decreasing at the 20 hour mark.
In other words, fasting improved negative moods among women with bulimia but it generally worsened negative moods among healthy women.
This helps us understand why someone with bulimia would be encouraged to fast for extended periods. She might find that her negative mood improves the longer she fasts. In contrast, someone without an eating disorder may feel a temporary improvement in negative mood when fasting, but after a few hours pass, she would quickly start to feel worse.
It can be hard to break patterns of fasting, binging, and purging when there is a short-term “reward” for some of these behaviors. Hopefully understanding these patterns might help with recovery.
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Dr. Gupta is a professor at Barnard College of Columbia University and provides individual therapy atTribeca Psychology
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