It’s not just your figure that changes when you lose weight: losing weight also causes major changes in the composition of bacteria in our intestines and in our brain activity – which also influences each other.
For many, the time around Christmas and New Year is a time of conviviality, charity and… lots and lots of food. We often want to lose those extra pounds quickly, making ‘losing weight’ one of the most popular New Year’s resolutions. But no matter how easy it is to gain weight, it can be difficult to lose that weight again. Our intestines, hormones and our brain all influence our weight and our eating behavior. But what happens if you do manage to lose weight? Does this also affect our body the other way around? Chinese scientists investigated this.
They specifically examined overweight people who followed a special diet: intermittent energy restriction or ‘periodic energy limitation’. This meant that participants sometimes had days when they ate very little and sometimes days when they ate normally. This diet lasted a total of 62 days and consisted of two parts. In the first part, the participants received special meals from a dietician, with fewer and fewer calories. Until the meals ultimately contain only a quarter of a normal food intake. In the second part, participants were given a list of healthy foods to choose from, which amounted to approximately five hundred calories per day for women and six hundred calories per day for men.
Diet results
The researchers were particularly curious about the relationship between the bacteria in the intestines, the brain and eating behavior. That is why they examined those aspects of the participants’ health before, during and after following the diet. To do this, they examined the feces, took blood samples and did brain scans. This showed, among other things, that the diet worked well for this group to lose weight: the participants lost an average of 7.6 kilos. They also had less fat, a smaller waist, lower blood pressure and better blood sugar levels, cholesterol levels and liver function.
The influence of bacteria
But following the diet also affected gut bacteria and brain activity. For example, after the diet, the researchers observed that there was less brain activity in the areas involved in appetite and addiction. They also saw that the ratio between different types of intestinal bacteria changed. For example, the share of species decreased Escherichia coli, Coprococcus comes in Eubacterium hallii – species that inhibit the area of the brain known to be important for a variety of executive functions, including the willpower to lose weight. In contrast, the species Parabacteroides distasonis in Faecalibacterium plautii actually more active – bacteria that influence brain areas related to attention, suppressing impulses, emotions and learning.
Your weight determines your food choice
Attention to this changed brain activity is very important, says Qiang Zeng, one of the researchers. “Overweight is one of the biggest health problems of our time. There are all kinds of ways to lose weight quickly, but maintaining a normal weight throughout your life is a lot more difficult.” Ironically, your weight also determines your food choice, says Zeng. “Look at the people around you. Who can resist a nice piece of cake, when the choice is there? Slim people often naturally choose food with few calories, while overweight people often tend towards food with many calories.” And that could well be due to the interaction between the intestines and the brain.
We overestimate how healthy we eat
We all know that healthy eating is very important. This is mainly because it significantly reduces the risk of various diseases – including the risk of cardiovascular disease, stroke and Alzheimer’s disease. However, it often proves difficult to maintain a healthy diet. But surprisingly, most of us still seem committed to eating healthy even when we’re not, a 2022 study showed. Of the more than 9,700 participants, about 8,000 (about 85 percent) rated their diet quality inaccurately. Of those, almost everyone (99 percent!) overestimated the healthiness of the diet. This means that we massively think that we eat healthier than is actually the case. But that is not even the most surprising thing, according to researcher Jessica Thomson. “What we found most surprising is the extent to which people overestimate the healthiness of their diet,” she previously told Scientias.nl. “For example, they perceived their diet as very good, while in fact their diet was poor.”
Interaction of intestines and brain
“The gut microbiome influences energy balance and also interacts with the brain through what we call the ‘brain-gut-microbiome axis’,” says Zeng. Numerous scientific studies have already shown that this axis is involved in the development of obesity, but exactly how communication works is not yet clear. This research also struggles with this. It seems clear that the observed changes are related to each other, but what exactly are the causes and what are the consequences is not. “We think the bacteria in the gut talk to the brain in a complex, bi-directional way. The bacteria produce substances that reach the brain via nerves and the blood. Conversely, the brain regulates eating behavior, while the food we eat changes the composition of the bacteria in the intestines,” says researcher Xiaoning Wang.
Follow-up research
While there are still unanswered questions about whether changes in the gut microbiome cause changes in the brain or vice versa, Zeng says these findings do provide a direction for further research into how the communication between the gut microbiome and the brain affects weight loss. According to fellow author Liming Wang, the next question is how exactly the bacteria in the intestines and the brain communicate in overweight people, even when they lose weight. “For example, which specific bacteria in the intestines and which brain areas are specifically important for successful weight loss and maintaining a healthy weight?”
The researchers hope that this will give us a better understanding of the role of intestinal bacteria and the brain in obesity and weight loss, in order to not only contribute to new ways for people to lose weight, but also to stay healthy.
2023-12-29 11:15:45
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