Intermittent fasting can help you lose weight, but it can also affect your brain. A new study from researchers at the Health Management Institute in Beijing found that an intermittent fasting diet, called intermittent energy restriction (IER), can dramatically change gut bacteria and brain activity, with both positive and negative results.

According to the New York Post, the diet involves restricting eating with periods of fasting. In the new study, participants lost an average of 17 pounds in two months. But they also showed changing patterns in areas of the brain involving the regulation of appetite and addiction. And the scientists found that there was “an increase in certain gut bacteria that can help with attention, motor inhibition, emotion and learning.”

Understanding the relationship between brain activity and gut microbiome could shed light on the factors involved in successful dieting and weight management, said the researchers. The full findings of the study were published in the journal Frontiers in Cellular and Infection Microbiology.

Professor Qiang Zeng and his colleagues at the Health Management Institute monitored the gut microbiome, blood and brain activity of 25 obese Chinese adults with an average age of 27 years, says Newsweek. In the study, participants underwent a “high-controlled” fasting plan where they spent 32 days eating meals that slowly decreased in calorie count to about one-quarter of their typical intake. Then, they were asked to follow a “low-controlled” plan in which they were given a choice of foods to eat and the diet consisted of 500 calories daily for women and 600 for men.

Besides the weight loss, the researchers noted that the gut bacteria were significantly altered in the study subjects who fasted. Some species, such as E. coli, decreased in numbers, while others increased sharply.

E. coli is a common bacterium that can cause sicknesses such as diarrhea, urinary tract infections, respiratory illness, and pneumonia.

“Significant alterations were observed in certain gut bacteria abundances due to the IER diet, including pathogenic E. coli as well as obesity-related probiotics,” said Zeng. “However, it should be noted that data regarding the gut microbiome is extensive; therefore, further research is required to explore specific microbial populations involved in weight loss.”

The changes in the gut microbiome triggered certain changes in the brain, said the researchers. For example, regions of the brain associated with the regulation of appetite and addiction saw decreased activity levels after the fasts. On the other hand, areas of the brain associated with attention, motor inhibition, emotion and learning had increased level of activity.

The researchers explained that the gut microbiome communicates with the brain in a “complex, two-directional way.” The gut microbiome produces neurotransmitters and neurotoxins which access the brain through nerves and blood circulation. In return, the brain controls eating behavior, while nutrients from our diet change the composition of the gut biome, said the study authors.

The researchers said that the next step is to find out exactly how the gut microbiome and the brain communicate in obese people to formulate a plan for successful weight loss and management.