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While it may be possible for some people to lose weight by only eating fast food, experts warn consuming high amounts of ultra-processed food can pose numerous health risks. Westend61/Getty Images
  • Kevin Maginnis, 57, from Tennessee, has gained TikTok fame for going on an All-McDonald’s diet, swearing it’s helping him lose weight.
  • Maginnis isn’t the first person to say the All-McDonald’s diet has helped him lose weight, but nutrition experts caution it’s not healthy for several reasons.
  • Consuming a diet that heavily relies on fast food can significantly increase the risk of chronic health conditions like heart disease and type 2 diabetes.

Kevin Maginnis’ weight loss journey began in February. The 57-year-old from Tennessee shared it on TikTok (because it’s 2023). His method is unconventional.

“I know some of you are thinking that might be crazy, but I’m gonna eat nothing but McDonald’s for the next 100 days,” Kevin Maginnis told followers in his first TikTok video.

Maginnis, who posts under @bigmaccoaching, has amassed 77K followers since February. He’s also lost 40 pounds in 56 days.

He announced his progress on Monday with a celebratory sausage, egg, and cheese burrito.

However, his diet plan runs contrary to standard nutritional advice.

“Fast food is a part of the American diet and has been associated with high caloric intake and poor diet quality,” the National Center for Health Statistics (NCHS) stated in a 2018 brief on fast food consumption among U.S. adults from 2013-16.

So, if this kind of diet is so unhealthy, why is Maginnis having success?

Experts dished on the reason he’s losing weight and why they don’t consider the All-McDonald’s diet one full of meals that’ll make your body happy.

Maginnis eats three McDonald’s meals and one snack per day. But his not-so-secret sauce: He’s half-sizing meals to supercharge his weight loss.

So, if he has a burger and fries, he’ll eat half of each and save the other half for another meal. In a Feb. 21 video announcing his plan, Maginnis said he wanted to show people that it’s not so much what you eat but how much you eat.

Maginnis is also skipping soda and drinking water.

A 2020 study indicated that soft drink consumption was associated with weight gain, regardless of physical activity levels.

Experts say that the calorie deficit is tipping the scales in Maginnis’ favor.

“This approach is working for him because he is consistently able to stay in a calorie deficit,” says Dr. Charlie Seltzer, a Philadelphia-based doctor board-certified in obesity medicine and internal medicine who did a TikTok live with Maginnis. “If you were eating fewer calories than you are burning, you will lose weight no matter what it is you are eating.”

Maginnis’ approach may seem surprising, but it’s not new.

John Cisna claimed he dropped 56 pounds, reduced his cholesterol, and nixed a total of 21 inches off his chest, waist, and hips on an all-McDonald’s diet for six months. The Iowa science teacher became a brand ambassador.

But a two-person case study isn’t enough to get the all-McDonald’s diet a stamp of approval from those who follow nutrition science.

“There are lots of ways to lose weight — some healthful and others not-so-healthful and everything in between,” says Virginia-based Jill Weisenberger, MS, RDN, CDCES, CHWC, FAND, author of Prediabetes: A Complete Guide, Second Edition. “I could lose weight by…swallowing a tapeworm or by eating small amounts of food at fast food restaurants. I wouldn’t recommend any of these…ways for good health…He would lose weight on a similar calorie deficit whether he ate only apples, only jellybeans, or only McDonald’s meals.”

Seltzer notes that weight loss has its benefits. For instance, losing weight can help reduce disease risk.

Research from 2017 indicated that modest weight loss was important for people diagnosed with prediabetes who were living with overweight or obesity.

A March 2023 review of 124 studies with more than 50,000 participants suggested that losing extra weight could benefit the heart even if a person gains some of it back.

But weight loss and the number on the scale are not the be-all, end-all of health.

Weisenberger says other markers of overall health include:

What’s more, how you lose weight matters.

“Rapid weight loss through fad diets or extreme calorie restriction can be harmful to the body and may lead to nutrient deficiencies,” says Beata Rydyger, BSc, RHN, a registered nutritionist based in Los Angeles and clinical nutritional advisor to Zen Nutrients.

Indeed, though a 2022 review did not study the all-McDonald’s diet, it did note that compliance with fad diets like keto and detox diets were concerning, in part because of nutritional deficiencies from eliminating one or more essential food groups.

Though Maginnis’ approach hasn’t been studied, the effects of fast food consumption in general have.

A 2018 study linked fast food consumption with higher abdominal obesity, while 2019 research indicated an association between ultra-processed food and a higher risk of cardiovascular disease.

“Consuming a diet that heavily relies on fast food such as McDonald’s can significantly increase the risk of chronic health conditions like heart disease and type 2 diabetes due to the high levels of saturated and trans fats, sodium, added sugars and additives found in these foods,” Rydyger says.

But McDonald’s foods can have nutritional value.

“Typical fast foods like burgers, chicken nuggets, and french fries are a mixed bag,” Weisenberger says. “Certainly, the beef, chicken, and potatoes provide valuable nutrients, but they usually come packed with extra calories, saturated fats, or sodium — sometimes all three.”

Still, Weisenberger says what’s in the all-McDonald’s diet is as problematic as what’s not in it — ample amounts of fruits, vegetables, whole grains, and pulses (lentils, beans, and peas).

“This leads to a deficit of vitamins, minerals, fibers, and disease-fighting phytonutrients,” says Weisenberger. “By eating McDonald’s meals only, it’s not possible to provide adequate fibers for the gut microbiota or to consume enough polyphenols to reduce inflammation and fight chronic disease.”

The variety doesn’t just lead to nutritional deficiencies — it can get boring.

“[It’s] probably not sustainable due to the lack of variety,” says Vanessa Rissetto, RD, a registered dietitian and CEO of Culina Health. “I would personally tire of eating burgers and fried foods day in and day out and being only able to eat one type of fruit or lettuce.”

And Rissetto fears that the focus on weight and calorie counting can affect a person mentally, too.

“Obsessing over calorie counting and every single thing you eat isn’t great for your mental health, and we want to think about how we are communicating to people about what is “healthy” and how they can achieve that health,” Rissetto says.

The all-McDonald’s diet’s lack of sustainability may be a silver lining — this diet is one to ditch guilt-free, experts say. Instead, Rydyger emphasizes that variety is the spice of life and the hallmark of a good diet.

“Eating a diverse array of foods is helpful because it ensures that the body receives all of the necessary nutrients for optimal health,” Rydyger says. “Different foods contain different nutrients, so consuming a variety of foods helps ensure that the body receives all of the necessary vitamins, minerals, and macronutrients.”

One such diet, the Mediterranean, has topped the U.S. News & World Report’s list of best diets for six-straight years. (The all-McDonald’s diet didn’t make the cut.)

The Mediterranean diet has been linked to numerous improved health outcomes, including longer lifespans and lower heart disease in women.

Rydyger didn’t name names when emphasizing a good diet plan. But she offered some advice on crafting one without labeling it a certain meal plan.

“A better diet plan for overall health involves consuming a balanced diet that includes a variety of whole foods, such as fruits, vegetables, whole grains, lean proteins, and healthy fats,” Rydyger says.