Will this eating plan work?

Meat three times a day?

He probably lost weight because he was eating in a calorie deficit. If what you eat results in a calorie deficit, you will lose weight. If your 2 days you eat anything you want takes up the deficit you created the other 5 days, then you will not lose weight.

Having more protein and fats and less focus on carbs on those days may have helped him keep fuller, longer resulting in less eating which means less calories.

I've tried something like this diet in the past and it didn't work for me. I got too hungry...I needed some complex carbos (I think that's what they are called) such as bread or rice. I also like fruit a lot. When my friend did a diet like this, it caused her gallbladder to act up. She said this happens to some people with this kind of diet.

But if it works for you, great! I might suggest adding 2-3 servings of fruit and a few servings of bread/rice. But everyone's body is different. I dont' do well on a very restricted diet...I tend to go AWOL after a week or 2. I do better on a diet with "Everything in moderation."

Also, the problem with the kind of diet you mentioned, for me the problem was when I'd go to a party, potluck, out to eat, etc. So for me, everything in moderation and watching portion sizes carefully works well.

I can easily undo five days of hard work in two days of doing what I want. That is one way to maintain. Also, I get really, REALLY moody when I don't get my fats and complex carbs.

This. I can be my lowest weight on Friday and be up 5 pounds on Monday just from what I ate on the weekends! I get it back down by Friday again, but it starts all over. I am pretty much at maintenance by doing that. I have to check my weekends to make forward progress happen again. I would watch out for that.

Will this put you at a calorie deficit for the week?
Is yes, then you will lose weight.
If not, then no, you will not lose weight.

If you burn 2000cals/day, and your daily intake goal is 1500cals, then you are at a 500cal deficit. Over a week that would be a 3500cal deficit.
Done the other way your weekly burn goal would be 2000*7=14,000cals, and your weekly intake goal would be 1500*7=10,500cals, for a 3500cal deficit.
One way is 1500*7=10,500,
the other might be 1200+1800+1200+1200+1200+2200+1600=10,500
To me, the varied one seems more like how people live.

Sounds awful!!

I can easily undo five days of hard work in two days of doing what I want. That is one way to maintain. Also, I get really, REALLY moody when I don't get my fats and complex carbs.

This. I can be my lowest weight on Friday and be up 5 pounds on Monday just from what I ate on the weekends! I get it back down by Friday again, but it starts all over. I am pretty much at maintenance by doing that. I have to check my weekends to make forward progress happen again. I would watch out for that.

So over Sat & Sun you eat an extra (3500*5=17,500) calories above your maintenance goal? What are you doing, drinking shots of olive oil while snacking on butter?

Yes. I really enjoy my shots of olive oil. Don't knock it 'til you try it. It helps to rinse down my fried sticks of butter.

It's cool to be a ****.

I can easily undo five days of hard work in two days of doing what I want. That is one way to maintain. Also, I get really, REALLY moody when I don't get my fats and complex carbs.

This. I can be my lowest weight on Friday and be up 5 pounds on Monday just from what I ate on the weekends! I get it back down by Friday again, but it starts all over. I am pretty much at maintenance by doing that. I have to check my weekends to make forward progress happen again. I would watch out for that.

So over Sat & Sun you eat an extra (3500*5=17,500) calories above your maintenance goal? What are you doing, drinking shots of olive oil while snacking on butter?

Yes. I really enjoy my shots of olive oil. Don't knock it 'til you try it. It helps to rinse down my fried sticks of butter.

It's cool to be a ****.

There are 500 calories in 2 pieces of papaginos fried ravioli.
There are also 500 calories in 2 pieces of fried mozzarella from most restaurants.
I could go on.
It's not hard to eat an extra 3,500 calories a day, tbh.
Don't get me started on mixed drinks and frosting.

5lbs in 2 days...

Let me paint you a picture:
280oz of Ben & Jerry's Cherry Garcia (Not the diet version) = 17,463cals.
154oz of Starbucks Caffe Mocha with whipped cream = 17,463cals
74 pints (9.25 US gallons) of Guinness beer = 17,540cals
21 sticks of butter w salt (5.25lbs) = 17,086cals
10 cups of olive oil (0.625 US gallons) = 17,280cals

So, pick one or a combo of them all, and eat all of that plus all your normal food, plus any deficit you have in 2 days, and you can gain 5lbs of fat in 2 days.

I can easily undo five days of hard work in two days of doing what I want. That is one way to maintain. Also, I get really, REALLY moody when I don't get my fats and complex carbs.

This. I can be my lowest weight on Friday and be up 5 pounds on Monday just from what I ate on the weekends! I get it back down by Friday again, but it starts all over. I am pretty much at maintenance by doing that. I have to check my weekends to make forward progress happen again. I would watch out for that.

So over Sat & Sun you eat an extra (3500*5=17,500) calories above your maintenance goal? What are you doing, drinking shots of olive oil while snacking on butter?

Yes. I really enjoy my shots of olive oil. Don't knock it 'til you try it. It helps to rinse down my fried sticks of butter.

It's cool to be a ****.

There are 500 calories in 2 pieces of papaginos fried ravioli.
There are also 500 calories in 2 pieces of fried mozzarella from most restaurants.
I could go on.
It's not hard to eat an extra 3,500 calories a day, tbh.
Don't get me started on mixed drinks and frosting.

5lbs in 2 days...

Let me paint you a picture:
280oz of Ben & Jerry's Cherry Garcia (Not the diet version) = 17,463cals.
154oz of Starbucks Caffe Mocha with whipped cream = 17,463cals
74 pints (9.25 US gallons) of Guinness beer = 17,540cals
21 sticks of butter w salt (5.25lbs) = 17,086cals
10 cups of olive oil (0.625 US gallons) = 17,280cals

So, pick one or a combo of them all, and eat all of that plus all your normal food, plus any deficit you have in 2 days, and you can gain 5lbs of fat in 2 days.

But it isn't 5lbs of fat gained in 2 days. It also isn't 5 lbs of fat lost over 5 days. If I drink a lot and eat a lot of salty, cheesey goodness - I am a bloated, hungover mess the next day. Which means greasy food. The 5 lbs is change in water retention, fat, muscle, poo, etc. And putting my body through five days of being good and then two days of binge eating just did not work for weight loss. (for me - I do know some people "relax" on the weekends and it doesn't involve mass quanities of food and alcohol)

And some women, at a normal weight, with a healthy diet, can gain 5lbs right before their period. Also - not 5lbs of fat gained.

Fluxuations in the number on the scale is not just changes in fat.

Depends on your definition of "doing what you want".

Regarding the diet it sounds really boring, repetitive and unsustainable long term. So my instinct is to say no, it won't work. Eat food you enjoy, get more exercise and monitor your portion size to ensure you're at a calorie deficit. You don't need to overcomplicate things.