Fit Person ONLY Eats McDonalds For 30 Days



Can you lose weight eating only junk? It sounds ridiculous, but we decided to put it to the test. For the next 30 days, I’ve convinced Brendan, my videographer, to eat only Mcdonalds every day to see if a weight loss diet that works really is as simple as calories in, calories out. Or, if the McDonald’s diet has consequences on his body and health that I never could’ve expected. To see the McDonalds diet effect on Brendan, he’ll not only be doing a DEXA scan to measure his body fat and muscle mass, but we’re also conducting pre and post-blood tests. We’ll also be testing Brendan’s strength before and after the experiment to give us another way to assess if he’s lost any of his hard-earned muscle and strength.

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But for now, it’s time to create a McDonald’s diet plan that’ll help him lose weight. Based on Brendan’s current weight, he’ll need to eat a daily target of 2000 calories. But to avoid losing muscle and ending up weaker after the 30 days, he’ll also need to hit a bare minimum of 120 grams of protein. But Dr. Layne Norton explains that the diet may get monotonous after a while, which reduces satisfaction and adherence. So, using Layne’s advice, the meal plan I made for Brendan consists of 3 meals and 2 snacks per day. But rather than locking him into a strict meal plan, I gave him a few different options for each meal. He’ll be logging everything into our new BuiltWithScience+ app. So, as long as he stays within his daily calorie and protein targets, he can modify the meals however he likes.

However, as it turns out, not every healthy meal option I selected for his Mcdonald’s weight loss diet was available in Canada. So, he had to start getting creative — like making his own salad out of his wrap. Brendan also started complaining about his racing heart. Honestly, though, I don’t think Brendan’s racing heart has much to do with his new diet. That’s because he’s not only been drinking extra coffee to help with his hunger, but he’s also pretty nervous about what this diet might do to his health. Almost every item on the McDonald’s item is full of saturated fat, highly refined, and stripped of pretty much everything that makes them good. As a result, aside from sodium, he’s not even close to getting even just 50% of most of his recommended nutrients every day.

On day 5, Brendan shared 2 common problems he ran into while eating McDonalds every day. He doesn’t always get the order he requests, which means more calories. And he’s having some … well, difficulties in the toilet. The recommended fiber intake for Brendan is about 35 grams a day. On his McDonald’s meal plan, however, he’s getting less than a third of this, barely reaching 10 grams daily. The “blockage” he’s experiencing has definitely made accurately tracking his weight loss a lot more difficult than anticipated. While Brendan was blaming his lack of progress on his low fiber intake, I wasn’t fully convinced.So I did some deeper investigation.
… and I came up with 2 reasons for why Brendan couldn’t lose weight eating only junk despite supposedly being in a calorie deficit. First, Mcdonald’s was severely under-reporting the calorie contents of their food. Second, the body absorbs more calories from a highly processed diet than a less processed one. So, with Brendan’s heavily processed diet, he may not be in the calorie deficit we initially thought he was, especially with the “hidden calories” that McDonald’s doesn’t seem to take into account. Which means… no more butter on his breakfast sandwiches and no sauces on his wraps and burgers.

So, what was the Mcdonalds diet effect on Brendan after 30 days? Overall, Brendan managed to gain 2 extra reps on his bench and pull-ups, and matched his deadlift strength although he forgot to wear wrist straps, limiting his strength. As for his blood work, The main things we’re looking for are his cholesterol levels, his HbA1c, which is the best blood marker for diabetes, his inflammation levels, and his liver health. Normally, all of these would be negatively impacted by a junk food diet. But what actually happened? Nothing. All his blood work stayed pretty much the same, which is surprising. It turns out weight loss alone is a major health booster and can “balance out” the negative effects you’d expect from a nutrient-deprived, junk food diet. Which now begs the question. What actually happened to Brendan’s weight, fat, and muscle mass? After only eating McDonald’s for 30 days, Brendan dropped 5lbs on the scale, lost three cm off his waistline and according to the results of his DEXA scan … dropped from 23% body fat percentage to 22% BF. Ultimately, this shows fat loss really is a numbers game.

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45 Comments

  1. 7:45 WHAT are you talking about? You are doing a video, even if you WEREN'T, you go back in and FIX the order, but especially since you are on a set schedule and a plan you are filming, why the hell would you not go back in and make sure the order was right?

  2. 6:17 lmao HOW do people have this stuff happen, unless he's being massively melodramatic, you just work out hard, and feel like it, your heart isn't "pounding out of your chest" unless you are fat and lazy which he clearly isn't.

  3. Imagine being so anxious about the fibre, sat fat, nutrition in MacDonalds meals, when he normally eats clean. They aren't even adding sauce. It's not as bad as they think, it's basically a normal sandwich.

  4. 3 minutes into the video and I'm so pissed that you get to have the grilled chicken sandwich where you are. I'm the United States Chick-fil-A is the only fast food restaurant that carries a grilled chicken sandwich. Wendy's has one only at select locations (none near me). I just don't really like fried chicken sandwiches, they aren't that good to me, but I do sometimes crave a fast food grilled chicken and I'm out of luck

  5. the second you said the muffin was 290 i was like aint no way that is 290 calories. As someone who counts calories religiously, my sus alarm was going off.

  6. I’m wondering about salt as well.. my son loses 8-10 lbs at wrestling practice. We he starts back in with electrolytes. He’s able to gain it all back in a day, which not a big deal he’s always at his target, but he absolutely needs it for his blood pressure to stabilize

  7. I understand his cravings for healthy food while only eating McDonalds.When I was in
    My first trimester with my three pregnancies I could only only down crappy foods no matter how I try to add work around it.I consistently craved the healthy foods that I couldn’t hold down and even the ones I didn’t normally eat,I remember crying because I just wanted a salad but could only hold down ramen and chicken nuggets

  8. "You can eat whatever you want as long as you stay active" Is a phrase that I heard from physically active friends, and I never believed that it seems to be true.

  9. Mcdonalds is actually amazing. I eat really healthy but i always have a whole mcdonalds meal aswell as healthy food because its so easy to get those 2000 calories in while eating other stuff for protein and vitamins and stuff. Works surprisingly well.

  10. Even just cooking and cleaning is an effort, so I never wanted to add counting calories and macros and protein and fiber to what I have to do to eat.
    But I’m considering it from this.

    I think this experiment might have different results with a female though.
    The hormones and cycle, especially one with PCOS, it doesn’t seem that simple to reduce fat.

  11. Such diets are simply not sustainable long term. So the fact you can lose weight eating just about anything over 30 days as long you maintain a calorie deficit is pretty much irrelevant.

  12. I eat 2 smors yesterday just to get into my range for the day…had no idea how few cal. I could eat and struggle to get my cal up I still got about 150g of protein as well.

  13. He’s really not going about this the right way. He needs to be adding protein to his meals (extra beef patties, eggs, etc) to improve the protein to carbs ratio. Really nothing wrong with McDonald’s but he needs to learn to customize his meals for better macros. Also remove crap like mayo and sauces.

  14. University students actually made a documentary after the movie Super Size Me. They called it Portion Size Me and basically did this. They lost weight.

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