Can You Really Lose Weight on a McDonald's-Only Diet? It's More Complicated Than You Think

Is it possible to lose weight while eating a diet consisting solely of fast food from McDonald’s? According to Tennessee grandfather Kevin Maginnis—aka @bigmaccoaching on TikTok—you can.

Maginnis, 56, began documenting his McDonald’s-only diet on the social media platform in February. His goal: to eat McDonald’s morning, noon, and night for 100 straight days, to show himself and his followers “that it’s not as much what you’re eating, it’s the quantity that [you’re] eating.”

His plan was widely received on TikTok before the platform banned his account. Maginnis’ first video garnered more than 2.2 million views—but that doesn’t mean this diet trend comes free from controversy. Though Maginnis has lost weight so far on his unconventional plan—down 21 pounds since his last weigh in—many experts are concerned not only for his health but also potentially the health of people who are inspired by him.

Here’s what you need to know about Maginnis’ McDonald’s-only diet, why it might be leading to some weight loss, and why the results may not necessarily be healthy or sustainable.

What Is This McDonald’s-Only Diet?

The McDonald’s-only diet is not an official eating plan—it was not created by registered dietitians and there are no clinical trials available to evaluate its safety or effectiveness.

The diet was created by Maginnis himself, on February 21, according to his TikTok videos. The diet only has a few simple rules:

• Maginnis is to eat only food offered on the McDonald’s menu for 100 days.
• Three meals are permitted each day, and each meal portion is cut in half, so only 50% of each menu item is consumed. (Desserts are permitted, as well.)
• No snacks are allowed between meals, and Maginnis has elected water as his beverage of choice.
  

An exercise recommendation is not included on this plan, and Maginnis claims he only gets in around 2,000 steps daily.

Desiring to reach a healthy weight, Maginnis said he tapped into his past experiences being an ex-wrestler and boxer. Since calorie restriction helped him lose pounds and inches in the past, he decided to try limiting portion sizes at his beloved fast food joint and only eat when he is hungry. 

Can You Really Lose Weight by Eating Only McDonald’s?

According to his most recent TikTok update, Maginnis has been on his diet for 21 days and he’s lost 21 pounds.

The reason for that, largely, is calorie restriction. “The reason [Maginnis] is losing weight on this diet is because he is consuming fewer calories than he is burning each day,” Lainey Younkin, MS, RD, LDN, weight loss dietitian at Lainey Younkin Nutrition, told Health.

Maginnis’ weight loss isn’t necessarily surprising to experts. Idrees Mughal, MBBS, a Britain-based physician with an additional masters in nutritional research, said that when the goal is purely weight loss, “how much you eat is more important than what you eat.”

What he’s eating may also be contributing to the weight loss. “He is consuming protein at each meal, which suppresses appetite and keeps you full longer,” Younkin said. “This could be leading to less snacking than he was doing before and a calorie deficit at the end of the day.”

But whether his weight loss will be sustainable and able to be maintained is yet to be determined. “The true test won’t actually be whether or not he can lose the weight—many different calorie deficit diets lead to weight loss—it’s whether or not he will keep it off,” registered dietitian Sarah Anzlovar, MS, RDN, LDN, owner of Sarah Gold Nutrition, LLC, told Health.

According to Anzlovar, “most people regain weight lost within six months to one year because bodies increase the drive to eat and metabolism often slows down with weight loss.” Once someone like Maginnis stops his weight loss experiment, “he will need to maintain a significant calorie deficit in order to maintain the weight loss,” Anzlovar said.

Mughal agreed that while it is true that in the short term, simply reducing the amount you are eating can offer some health benefits, it likely won’t be a sustainable strategy. “Both quality and quantity of food impact weight loss for long-term success,” he said.

What Are the Health Risks of a McDonald’s-Only Diet?

In addition to his 21-pound weight loss, Maginnis’ McDonald’s-only diet has also resulted in a reduction in many of his heart-health markers, including his triglycerides, LDL cholesterol, and total cholesterol, he said in his TikTok videos.

In the short term, heart health can improve among people with obesity who lose a significant amount of weight. “The weight loss will override the unhealthy dietary pattern,” Dr. Mughal said.

But unhealthy eating patterns will catch up with people who don’t prioritize diet quality. “Eventually, it will negate the beneficial effects of the weight loss,” Dr. Mughal said, adding that as one’s health journey continues, diet quality needs to become the focus without actively restricting calories to keep hunger cues and the risk of binge eating in check.

Weight loss and heart health markers aside, McDonald’s food is not nutritionally up to par to support overall health.

“McDonald’s meals significantly lack fruits and vegetables, which contribute important minerals, antioxidants, and fiber to your diet,” Anzlovar said. “This could not only significantly affect digestive health, but it could also lead to vitamin and mineral deficiencies unless a multivitamin is included.”

In fact, research has confirmed that these patterns among fast food eaters lead to poorer diet quality; higher intakes of total and saturated fats, sugar, and sodium; and lower intakes of fiber, dairy, fruit, vegetables, and micronutrients.

Underconsumption of nutrient-dense foods like produce, whole grains, nuts, and seeds is linked to an increased risk of many chronic diseases, including type 2 diabetes and coronary heart disease.

And while Maginnis may be getting a good amount of protein in his diet, the protein provided by many fast food establishments is often ultra-processed, which means it’s “loaded with sodium,” Younkin said, adding that ultra-processed foods have also been linked to high blood pressure, heart disease, and certain cancers.

“[But] since this is a short-term experiment, it’s hard to know exactly how much it will affect long-term health,” Anzlovar said.

What to Consider Before Trying a McDonald’s-Only Diet

Though Maginnis has seen some short-term success on his McDonald’s-only diet, experts certainly aren’t recommending others to follow in his footsteps.

For the most part, Americans are urged to follow the MyPlate method, which was developed to help people incorporate the recommendations established by the Dietary Guidelines for Americans. The method includes making half of your food volume fruits and vegetables at meals; with lean proteins, dairy, and quality carbohydrates making up the remainder of the plate.

McDonald’s food—or fast food in general—doesn’t neatly fit into those guidelines. “[I cannot] think of a single combination of a McDonald’s meal that would fit these goals,” registered dietitian and author Lauren Harris-Pincus, MS, RDN, told Health. “Especially since they no longer offer salads or grilled chicken on the menu.”

It’s also important to remember that weight loss alone doesn’t necessarily improve health markers over the long term.

“Research has shown that even with maintained weight loss, poor health habits, including diet quality can negatively affect metabolic markers such as cholesterol and blood sugar,” Anzlovar said. “On the flip side, incorporating healthy habits like eating fruits and vegetables and other health-promoting foods along with exercising can improve long term health.”

So while jumping on this TikTok trend may sound appealing, there are some long-term risks associated with eliminating entire food groups, especially if this diet is adopted for an extended period of time.

Because of this, trying any diet should be discussed with your healthcare provider beforehand—especially if it’s one that involves hitting the drive-through window multiple times a day, as it will not be an ideal match for most people who want to achieve long-lasting health benefits.