Gut health is no doubt one of the most important aspects of our overall wellbeing. Supporting everything from our immunity to our cognitive functioning, the gut plays a crucial role in helping us stay healthy. And while it’s often thought that cleaning up one’s diet is good for our microbiome, new research suggests there are certain diets that are a little too extreme for our sensitive tummies to handle — in fact, they can have major consequences.
Extreme Calorie-Restriction and Gut Health
A healthy gut contains a diverse array of bacteria that help us digest and assimilate nutrients from our food. In a new study published in the journal Nature, a team of researchers aimed to determine how restricting calories could impact this bacterial diversity. For the study, 80 overweight women were selected and monitored for 16 weeks. Half of them were instructed to adopt a medically-supervised, very-low-calorie diet, eating around 800 calories per day, for eight weeks. The other half of the group ate enough calories to maintain their existing body weight.
The researchers measured gut health by analyzing the bacterial make-up of fecal samples before, during, and after the trial. According to their findings, those eating the low-calorie diet did lose weight, but also showed major changes in their gut microbiota. In fact, the low-calorie dieters had significantly reduced bacterial diversity — a measure of good gut health. Lead authors of the study reported that dieting also changed the behavior of the remaining gut bacteria, making the women less able to absorb nutrients from their food. And if that weren’t bad enough, levels of one type of harmful bacteria called Clostridioides difficile increased significantly for the women in the dieting group.
High levels of Clostridioides difficile is often found in people who have recently taken antibiotics, and it’s known to cause severe diarrhea, fever, and inflammation in the colon (colitis). The subjects in the study didn’t show signs of these health problems, though the scientists suggest that more research over a longer trial period would need to be conducted in order to understand the long-term impacts. They agree, however, that the presence of more C. difficile raises some important questions about how our microbiomes react to weight loss.
“Our results underscore that the role of calories in weight management is much more complex than simply how much energy a person is taking in,” says one of the lead researchers, Peter Turnbaugh. “We found that this very-low-calorie diet profoundly altered the gut microbiome, including an overall decrease in gut bacteria.”
At the end of the day, having a diverse array of bacteria present in the gut is a true marker of good health, and extreme diets are clearly not a way to achieve it. So, even if you’re trying to lose weight, remember that being overly-restrictive can actually put your body in a worse position and cause more harm than good. On any journey to better health, it’s best to focus on nourishing yourself with whole, nutrient-dense foods, and of course, speaking to a qualified professional to help you come up with an eating plan that’s right for you.