In the world, more than a billion people are obese. Obesity is a risk factor for cardiovascular disease, diabetes and some cancers. But losing weight through permanent weight loss is not easy: complex interactions between body systems such as gut physiology, hormones and the brain are known to work against this process. One method for losing weight is intermittent energy restriction (IER), in which days of relative fasting alternate with days of normal eating.
Here we show that an IER diet changes the human brain-gut-microbiome axis. The changes observed in the gut microbiome and activity in addition-related brain regions during and after weight loss are highly dynamic and temporally coupled,” said lead author Dr. Qiang Zeng, a researcher at PLA General's Institute of Health Management Beijing Hospital.
The study is state published in Frontiers in Cellular and Infection Microbiology.
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The authors used metagenomics on stool samples, blood measurements, and functional magnetic resonance imaging (fMRI) to study changes in gut microbiome composition, physiological parameters, serum composition, and brain activity in 25 Chinese women and men obese people following an IER diet. Participants were on average 27 years old, with a BMI between 28 and 45, and weight loss was necessary.
“A healthy and balanced gut microbiome is critical for energy homeostasis and maintenance of normal weight. On the contrary, an abnormal gut microbiome can change our eating behavior by influencing some areas of the brain involved in addiction,” explained co-author Dr. Yongli Li of the Department. of Health Management of Henan Provincial People's Hospital, China.
First, participants underwent a 32-day “high-control fasting phase” in which they received personalized meals designed by a dietitian, with the caloric value gradually decreasing to a quarter of their baseline energy intake . They then spent 30 days in a “low-controlled fasting phase,” in which they were given a list of recommended foods: participants who adhered perfectly to this diet would receive 500 calories per day for women and 600 calories per day. day for men.
At the end of the study, their body weight had decreased by an average of 7.6 kg, or 7.8%. As expected, they had experienced a reduction in body fat and waist circumference.
Likewise, their blood pressure and serum levels of fasting plasma glucose, total cholesterol, HDL, and LDL were decreased, as were the activities of major liver enzymes. These suggest that IER helps reduce obesity-related comorbidities such as hypertension, hyperlipidemia, and liver dysfunction, as well as aiding weight loss.
The authors observed, despite weight loss, a decrease after IER in the activity of brain regions implicated in the regulation of appetite and addiction. Within the gut microbiome, the abundance of the bacteria Faecalibacterium prausnitzii, Parabacteroides distasonis, and Bacterokles uniformis significantly increased, while that of Escherichia coli decreased.
Further analyzes performed after weight loss showed that the abundance of E. coli, Coprococcus and Eubacterium hallii bacteria was negatively associated with the activity of the brain's left orbital inferior frontal gyrus, known to play a key role in executive functions, including our desire to lose weight. In contrast, the abundance of the bacteria P. distasonis and Flavonifractor plautii was positively correlated with the activity of brain regions associated with attention, motor inhibition, emotion and learning.
These findings suggest that changes in the brain and microbiome during and after weight loss are linked, either because they cause each other, or because another unknown factor causes both. Because the study is correlation, it cannot resolve the direction of underlying causality.
“The gut microbiome is thought to communicate with the brain in a complex, bidirectional manner. The microbiome produces neurotransmitters and neurotoxins that access the brain through nerves and blood circulation. In return, the brain controls eating behavior, while nutrients in our diet change the composition of the gut microbiome,” said co-author Dr. Xiaoning Wang from the Institute of Geriatrics at PLA General Hospital.
Co-author Dr. Liming Wang, also from the Health Management Institute in Beijing, said: “The next question to answer is the precise mechanism by which the gut microbiome and the brain communicate in obese people, including during weight loss through weight loss. Are the gut microbiome and brain regions critical to successfully losing weight and maintaining a healthy weight?”
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