We all know that a diet of regular fast food isn’t good for us, but just how unhealthy is it?
Most people remember the documentary Supersize Me, in which filmmaker Morgan Spurlock spent a month eating McDonald’s food exclusively. The results were significant: Spurlock gained weight, damaged his liver, and claimed to experience withdrawal symptoms when he stopped eating the food.
But what Spurlock’s experiment didn’t look at was the effect that all that junk food has on the delicate balance of bacteria in our gut.
The Significance Of Gut Health
Our gut bacteria are one of the most overlooked and important parts of our body – the balance of these fragile flora can affect everything from our digestion to our mental health(1).
Our understanding of these bacteria and how they influence our body’s functions has evolved significantly over the past few decades. Until relatively recently we viewed many of these bacteria as harmful – but as it turns out, only a small minority are bad for us, and most are essential for our well-being.
Fast Food Kills Gut Bacteria Diversity
As important as these bacteria are, they’re also quite fragile. Studies in lab mice have shown that diets high in fat and sugar can have a drastic negative impact on the diversity of our gut bacteria(2).
While probiotics like the kind found in yogurt and other fermented food and drink can help reverse some of this damage, the best defense when it comes to preserving your gut bacteria is a good offense: a healthy diet high in fiber and low in fat.
For example, a recent experiment that swapped the diets of a group of Americans with a group of Africans found that just two weeks of subsisting on a diet high in fat and low in dietary fiber negatively affected the Africans’ metabolism and gut bacteria, while the Americans who lived on the African diet for two weeks showed lowered markers for colon cancer risk(3).
A loss of bacterial diversity in the gut is also associated heavily with obesity(4), diabetes(5), and problems with the immune system(6).
An Experiment In Fast Food Consumption
When researching his recent book The Diet Myth, Tim Spector – a professor of genetic epidemiology at King’s College in London – decided to conduct a brief experiment to see first-hand the effects that a steady diet of fast food could have on gut bacteria.
Tom, his son and a final year student of genetics at the University of Aberystwyth, agreed to be the guinea pig for this experiment.
Spector had Tom commit to eating nothing but McDonald’s fast food for a total of ten days. At the end of each day, a fecal sample was taken and sent in to a lab to be analyzed.
In Tom’s own words:
“I felt good for three days, then slowly went downhill, I became more lethargic, and by a week my friends thought I had gone a strange grey color. The last few days were a real struggle. I felt really unwell, but definitely had no addictive withdrawal symptoms and when I finally finished, I rushed (uncharacteristically) to the shops to get some salad and fruit.”(7)
Ultimately, the experiment took a heavy toll. In just 10 days of consuming Big Macs, chicken nuggets, fries, and Coca-Cola, Spector’s son was found by laboratory fecal testing to have lost nearly 1,400 types of bacteria species from his gut – nearly 40% of his total.
Loss of diversity is a universal signal of ill health in the guts of obese and diabetic people and triggers a range of immunity problems in lab mice.
Keeping Your Gut Healthy
While most of us are unlikely to stop eating fast food altogether, hopefully this provides some incentive for those considering cutting down significantly on their fast food intake.
While fast food is not gut-friendly, there are foods that our gut bacteria seem to love and thrive on – these include probiotics like yogurts, root vegetables, nuts, olives and foods that are high in dietary fiber.
In other words, diversity in your food is great for diversity in your gut.