11 March 2016

Limiting junk food binges to the weekend is just as bad for the gut as eating unhealthy food all the time, say scientists, and can affect your health, including your mental health. This has implications for people who maintain a healthy diet throughout the week, but have weekend blowouts where they indulge in junk food.

Australian researchers have found that intermittent exposure to junk food over 16 weeks is enough to shift the gut bacteria in rats to match that of obese rats who are fed junk food consistently.

This is important because the composition and diversity of bacteria in your gut (known as the microbiota or microbiome) play an important role in regulating inflammation in the body and play a key role in obesity and overweight. What you eat influences the composition of this population of bacteria and other microbes.

A junk food diet, high in fat, sugar and processed foods, reduces the number of microbial species capable of metabolising flavonoids, which are believed to assist in weight loss and exert a protective effect on the brain, say the researchers. So aside from the empty calories in junk food,  you are actually having an adverse effect on the bacterial population of your gut, which is a not inconsiderable entity, given that we have at least as many bacterial cells as human ones in our bodies.

The researchers also found that rats who eat junk food intermittently show large swings in food intake, consuming 30% more energy than those rats who ate a healthy diet consistently.

What does this mean for you?

The results of this study suggest,  if we can extrapolate from the rats, that if you eat a healthy diet all week, only to binge on junk food at the weekends, then you may be undoing all your good work, and in fact, your gut health may be no better than someone who eats junk food consistently.

Professor Margaret Morris, one of the authors of the study, says a greater understanding of the role of energy-rich foods and dieting on microbial changes is important, given the prevalence of yo-yo dieting in Western countries.

Last Reviewed: 11/03/2016



Kaakoush NO et al. Alternating or continuous exposure to cafeteria diet leads to similar shifts in gut microbiota compared to chow diet. Molecular Nutrition and Food Research DOI: 10.1002/mnfr.201500815