Losing weight by intermittent fasting can 'drastically change' the way your brain works – both positively AND negatively

Intermittent fasting, touted by celebs including Hugh Jackman, Beyoncé and Kourtney Kardashian, could have major effects on your brain, a study suggests.

Scientists at the Health Management Institute in Beijing found intermittent fasting can drastically alter gut bacteria and brain activity, resulting in both positive and negative outcomes. 

The most popular form of the trendy diet – time restricted eating – sees people limit their food intake to eight to 10 hours a day, going without food for 14 to 16 hours. 

Another form of the diet involves alternating days of fasting, eating very little, with days of normal eating. 

Chinese researchers studied the effects of this method of intermittent fasting on overweight and obese participants and found the regime led to a decrease in brain activity that plays a role in appetite and addiction, as well as an increase in the gut bacteria linked to attention, emotion and learning.

The results could point to how intermittent fasting could do more for people than just help them lose weight. 

Dr Yongli Li, study co-author from Henan Provincial People’s Hospital in China, said a healthy gut was essential for maintaining overall balance and improved health across all areas of the body. 

Scientists at the Health Management Institute in Beijing found intermittent fasting can cause drastically altered gut bacteria and brain activity, with both positive and negative impacts

Researchers studied 25 overweight and obese participants from China who followed two different regimens of intermittent fasting diet for two months.

Participants were an average of 27 years old and had a body mass of index (BMI) ranging from 28 to 45. 

To show how fasting diets affected the body, participants gave stool samples, blood samples and underwent brain scans.

First, they ate their normal diet for four days so the researchers could assess their average daily energy intake.

This was followed by a 32-day ‘high-controlled fasting phase’ where participants were given personalized meals created by a dietician, with a caloric value that gradually decreased to a quarter of their basic energy intake.

Patients ate without restriction every other day and ate the restricted meals on the other days.

Following that was a 30-day ‘low-controlled fasting phase,’ where they were given a list of recommended foods but not the actual meals. 

Female participants would receive an allowance of 500 calories a day, while men received 600 calories.

The researchers noticed decreases after both fasting phases in the activity of brain regions implicated in the regulation of appetite and addiction. This may mean that people are more hungry.

Researchers saw increased activity in brain regions for attention, emotion and learning, meaning people may be better at carrying out tasks requiring those skills. 

In the gut microbiome, researchers saw the bacteria Faecalibacterium prausnitzii, Parabacteroides distasonis and Bacterokles uniformis increase sharply.

Faecalibacterium prausnitzii increases the immune system’s capacity to fight inflammatory interactions, while P. distasonis is thought to help alleviate obesity and Bacterokles uniformis enhances the gut barrier.

Meanwhile, E. coli bacteria decreased. The bacteria can help with appetite control by releasing hormones that tell the brain the body is full. With less E. coli bacteria, people may have less control over their appetite.

Participants also lost an average of 16.7 pounds during the study. 

Dr Li said: ‘A healthy, balanced gut microbiome is critical for energy homeostasis and maintaining normal weight.

‘In contrast, an abnormal gut microbiome can change our eating behavior by affecting certain brain areas involved in addiction.’

The study was published in the journal Frontiers in Cellular and Infection Microbiology.