Ask a Dietitian: Can You Really Lose Weight Only Eating McDonald’s?

Welcome to Ask A Dietitian, a new series in which Yahoo Canada delves into food trends and popular nutrition questions with registered dietitian Abbey Sharp.

Dietitian Abbey Sharp gives Yahoo Canada the scoop on the 'McDonald's 100 Day Diet' for weight loss in our new series Ask a Dietitian.

Dietitian Abbey Sharp gives Yahoo Canada the scoop on the ‘100 Day McDonald’s Diet’ for weight loss in our new Ask a Dietitian series.

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Contact a qualified physician before engaging in any physical activity or making any changes to your diet, medications or lifestyle.

You might not think that losing weight and eating only fast food go hand in hand, but for an American man it did.

Kevin Maginnis, known on TikTok as Big Mac Coach, has taken on a challenge to eat nothing but McDonalds for 100 days to try to lose weight.

He started his journey in February, eating only half portions of fast food for every single meal. On day 100, Maginnis was 58.5 pounds lighter.

Can you really lose weight by eating only McDonald’s?

People reported that the Tennessee man has also seen other significant changes in his health. After doing blood tests, his triglycerides were down 205 points and her cholesterol was down 65 points. He said he was “pre-diabetic before, up to healthy ranges now”.

How is it possible? According to a registered dietitian, that’s not that surprising.

RD Abbey Sharp said Yahoo Canada even if it worked for him, there are many reasons she wouldn’t recommend it.

Read on for everything you need to know.

What to expect on this diet: Expert

When thinking about eating only at McDonald’s for 100 days, expert Sharp had many worries.

“The first thing I thought about was how constipated I was going to be.”

Sharp explained that men need about 38 grams of fiber per day. She added that it’s “honestly difficult for the average person to follow on a normal balanced diet, which isn’t made up solely of French fries and Big Macs.”

A Big Mac combo, which includes a Big Mac burger and an order of fries, totals 820 calories and just six grams of fiber.

Bucharest, Romania - 01.28.2023: Closeup of sloppy assembled or cooked Bigmac burger taken away from McDonalds restaurant.A Big Mac burger contains only three grams of dietary fiber.  (Getty Images)

A Big Mac hamburger contains just three grams of dietary fiber. (Getty Images)

According to Sharp, that’s not enough. Especially if you only eat half portions.

“If we’re not snacking and just eating McDonald’s, iceberg lettuce on the burger isn’t going to cut it.”

In addition to expecting a lot of short-term constipation, Sharp said she would also be concerned about the microbiome of people on this diet, which “isn’t something we can analyze in a standard blood test set.”

The dietician also added antioxidants and micronutrients that may be missing with this meal plan. Sharp said having potatoes for nearly every meal would translate into “a lot” of vitamin C. But you’d be missing out on other unique antioxidants “that we know have specialized disease-fighting properties.”

Found in “a variety of colorful fruits and vegetables,” these include: lycopene, beta carotene, anthocyanins, and sulfur compounds.

Close up of various colorful raw vegetables.  The dietician claims that colorful vegetables have

The dietitian says the colorful greens have “specialized disease-fighting properties.” (Getty Images)

Weight loss and blood test

Despite missing key nutrients, Maginnis’ blood tests showed improvement.

“I wasn’t at all surprised when I heard that,” Sharp admitted.

“The reason he’s seen improvements in those standard blood measurements is because of the weight loss.”

She explained that losing just 10 percent of your body weight can improve your cholesterol levels and blood sugar levels, reducing your risk of type two diabetes.

“Sugar is not the cause of the disease itself,” she said.

“If you’re able to maintain a healthy body weight by eating McDonald’s, you could definitely look quite healthy on paper.”

Maginnis posted 'before and after' photos on TikTok to share her progress from day 1 to day 90. (TikTok/@bigmaccoaching)

Maginnis posted before and after photos on TikTok to share her progress from day 1 to day 90. (TikTok/@bigmaccoaching)

As for weight loss, Sharp said she’s not surprised by that either.

“You can lose weight eating anything. You can lose weight eating just butter and candy if you want,” she said, “as long as you’ve been able to successfully create a calorie deficit.”

Though she said eating half-sized portions of McDonald’s “can absolutely and does work” in social experiments with limited dates, it’s not a long-term weight-loss plan.

In real life, frequent consumption of fast food is more likely to lead to weight gain.Abbey Sharp

“In real life, frequent consumption of fast food is more likely to lead to weight gain, and the reason for this is that meals like McDonald’s have a low satiety to high calorie ratio.”

Simply put, food doesn’t make you feel full for a normal amount of time.

“If we were to prepare a 1000-calorie meal consisting of a large, massive salad with greens, lean proteins and whole grains, and healthy fats like nuts and seeds or avocados, you’d probably feel very full before you even packed your go.”

Another concern Sharp has with a McDonald’s-only diet is simply losing interest in food, another potential cause of weight loss.

Anonymous woman eating a healthy vegan plant-based salad in a bowl with avocado, cashews, micro greens, pok choy, chickpeas, tomato, lettuce, cucumber, sesame.  Flexible fatty acids and dietary fiber

Large servings of healthy fats and fiber can make you feel fuller. (Getty Images)

The expert said the novelty of Big Macs and potato chips would eventually wear off. “Food would stop tasting so amazing where you feel like you don’t even want to finish it anymore.”

Sharp explained that this is an evidence-based phenomenon called specific sensory satiety.

“You’re forced to eat the same thing every day. Over time, you’ll probably only want to eat the bare minimum to suppress hunger.”

She added that this “would also make that calorie deficit easier” as “you stop eating for any kind of pleasure.”

“There is no such thing as bad food”

Despite society’s negative connotations with fast food, Sharp says “there is no such thing as bad food.”

Instead, it’s about balance.

“That’s not how nutrition works, right? We have to look at diet and lifestyle in general to determine if that food or meal fits into that.”

This would definitely never be a diet I recommend for weight loss.Abbey Sharp

Even with McDonald’s and other fast food restaurants, “there are absolutely redeeming qualities.”

However, Sharp said that “this would definitely never be a diet I recommend for weight loss, nor would it be a diet I recommend for health.”

Just because it worked for one man in the short term, doesn’t mean it will work for everyone, she explained.

“Everyone has to find a way to eat that makes them feel good, that is sustainable for them.”

Let us know what you think by commenting below and tweeting @Yahoo Style CA! Follow us on Chirping AND Instagram.

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