Jumping between eating well during the weekdays and binging on junk food during the weekends is just as bad for your gut health as consistently eating junk food throughout the week, reports a new study from University of New South Wales (UNSW).
Published in the journal Molecular Nutrition and Food Research, the study was led by Prof. Margaret Morris, who is the head of Pharmacology at UNSW. The team examined the impact of yo-yo dieting, which is basically yo-yoing between junk food and good food, on the gut microbiota of rats.
In the human gut, around 100 trillion microbial cells reside that directly have a role in metabolism, nutrition, as well as immune function. Disruptions to these microbial cells are known to cause a number of gastrointestinal conditions such as inflammatory bowel disease or obesity.
Morris states that the study is the first to be able to compare on how continuous or irregular exposure to an unhealthy diet can affect the composition of the microbes living in the gut.
The findings of the research show that intermittent exposure to junk food for even just three days a week is already enough to shift the microbiota to the pattern that is seen in obese rats that have the diet continuously. A reduction in the diversity of the gut's microbiota and a loss of some of the beneficial biota is clearly not a good thing for health. While these findings are yet to be replicated in humans, those who are strict with their diet during the week may be undoing all their good work by hitting the junk food over the weekend, says Prof. Morris.
The research compared the abundance of microbiota in rats with either a continuous diet of healthy food or junk food, to a group cycled between the two diets, healthy food for four days, and junk food for three, in a period of three weeks.
Metabolic markers such as body weight, fat mass, as well as levels of insulin and leptin, were checked. After the period of 16 weeks, rats who had the cycled diet were already 18% heavier as compared to those who were eating the healthy diet, while levels of insulin and leptin were in between those of rats eating junk food and healthy food.
The researchers also saw that the microbiota in the gut of the rats having cycled diets were almost the same as those seen in the rats fed a constant diet of junk food. The gut microbiota of both of these groups was also significantly different from the rats eating a healthy diet.
The rats on the cycled diet also showed large swings when it came to food intake. They consumed 30% more energy as compared to those on the healthy diet. When the cycled rats switched back to the healthy diet, they ate only half as much as those consistently on the healthy diet.
Professor Morris says that better understanding of the role of energy rich foods and dieting on gut microbial changes is quite important, especially because of the present obesity epidemic and the prevalence of doing yo-yo dieting seen in Western countries.