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Ella Scott
A father designed a mandatory 10-day McDonald’s diet for his son to follow as part of his studies, and over a decade later, he’s still feeling the repercussions.
Nutrition can be a nightmare to navigate if you’re not clued up on what’s good and what you really should be avoiding.
For those of us who aren’t well versed in food, there’s: dietary guidelines in place to help us out, newly published guardrails regarding supplements, and a recently-introduced junk food advertising ban to help us reach for healthier snacks.
One man who wants to know first hand how his body digests and deals with certain foods is Tim Spector, Zoe founder and professor of Genetic Epidemiology at King's College London.
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The 67-year-old has been ‘experimenting’ on himself since 2014, trying various short-term diets on for size to see what the results would be.
This includes eating only unpasteurized French cheese for three days, and consuming noodles and strawberry milkshakes to understand their effects.
Whilst his son Tom was in his final year of university studying genetics, Tim used him as a guinea pig to notch up another nutrition-based experiment.
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When asked to come up with a good idea for his health-based dissertation, the epidemiologist put forth the idea of discovering what would happen to your gut microbes if you just ate fast-food for 10 days.
The family members selected McDonald’s, and the University of Aberystwyth alumnus was ordered to eat a Big Mac or Chicken McNuggets as well as fries and Coca-Cola for every meal.
For three days, Tom saw no changes. But after the fourth, it seemed as if he had begun to regret his decision.
In his article for The Telegraph, Tim explained that his son was complaining of nausea just four days into the exclusive menu.
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He noted how his wife, Veronique Bataille, a dermatology consultant, had said that the ‘fun had worn off’ and that perhaps their only child should ‘stop’ the greasy trial.
“I was tough,” the British doctor wrote. “’No, you don’t start a project and give up just because you’re not feeling well’. I was thinking like a scientist. If he’d got ill, I’d be thinking like a father.”
Despite initial misgivings and becoming lethargic, the student completed the McDonald’s diet.
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A sample of his stool was sent away and the results, delivered from Cornell University and the British Gut Project, were startling.
According to the expert, his son had lost ‘40 percent of his diversity of species or the richness of his gut.’ That’s around 1,400 types, as per his 2015 report in The Conversation.
“There’s probably no long-term harm done but my wife tells me I was terrible to do it,” he added.
“She doesn’t go along with my whims and thinks my research plans are crazy. When I’m away she eats steak and chips.”
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Tom stated that, every year, he and his family get their stool tested, and that his gut microbe has ‘never once returned to the baseline [he] had before the McDonald’s thesis’.
Want to get a handle of your health in 2026 but don’t want to miss out on your once-in-a-blue-moon McDonald’s?
Well, good news—a dietician has outlined some orders that won’t completely work against your grand plans.
“It is okay to indulge in a McDonald's meal every once in a while. One burger or order of chicken nuggets will not make or break your health goals,” said Lauren Manaker, a registered dietitian.
“Eating to support your health goals is ultimately all about portion control and knowing exactly what you are consuming.
Writing for Health, Manaker stated that Hash Browns, a small portion of Chicken McNuggets, and a regular hamburger are all on the ‘okay to eat’ list.
A classic McDonald’s cheeseburger and the Egg McMuffin can also be consumed as part of a balanced diet.
“An Egg McMuffin is a source of protein and vitamins B12, B6 (riboflavin), B5, and iodine. Eggs also provide choline, a nutrient that supports brain health,” she wrote, adding that you should ‘forego the bacon to cut down on sodium’.