Per this article he lost 100 lbs on a potato then veggies no exercise diet.
Penn Jillette Lost 100 Pounds Eating These 2 Things
His book describing it is here.
Presto!: How I Made Over 100 Pounds Disappear and Other Magical Tales
I’ve never heard of this diet and I’m not willing to lay out cash for the book. Anyone know how what he is describing is supposed to work? There is little or no info in articles or reviews about the specific mechanism involved.
Well how many calories are in a potato, 200? If all you eat in a day is a potato for breakfast, a potato for lunch and 3 potatoes for dinner, that would be 1000 calories and a pretty big calorie deficit for even the most sedentary of humans.
Vegetarian diets have worked for some people. At least you don’t have to give up carbs. Potatoes and other vegetables can be quite filling it’s probably just reduced calories. The key may be finding out what he ate before he went on the diet. I saw him on the TV last night pushing his book on a political show, no details, but he’s interesting enough I may just get hold of a copy anyway.
There’s a guy at my gym who has lost 200lbs.
I asked him how he did it, and he said “I figured out that I could eat exactly what I have always eaten - just less of it”.
It’s all about calories in vs. calories out.
Other articles have more details. The potatoes were just an arbitrary choice – the idea was to reduce to a single food (no butter or salt, just the potatoes) for a few weeks, then slowly add other foods back, aiming to “relearn” a healthier diet.
All non seasoned potatoes all the time? I’d think I’d get sick of that in a few days at most.
I imagine there is an element of “Ugh, potatoes again? I’d rather just not eat.” that enters into it as well.
It’s the old take in less calories than you expend.
The thing is potatoes have a horrible reputation for being high in calories and it’s not really true. A plain old potato has about (medium) has about 100 calories.
Did you ever eat a plain potato? Not much to get excited about. It’s all the delicious things we do to it, like fry it and all the toppings we put on it, that make the potato so good to eat and also make it so high in calories.
Hm, that would be an extremely low (as in: zero) fat diet. I’m not sure when the bad effects of not getting your essential fats kick in, but I sure wouldn’t try this without medical supervision.
Also, two weeks in meaningless. It’s his diet after the two initial weeks that’s relevant.
You have to eat about two kilos of potatoes a day to get your daily calories, they’re 80% water.
They are a surprisingly complete food, though: you get enough of most vitamins (like C) as well as a reasonable amount of protein. Just add some fat and you can pretty much live off of just potatoes.
I read that he said a big reason for doing it that way was to retrain himself in terms of his relationship to food.
One can imagine that if a person loves food and constantly thinks about what he might have for his next meal, he is likely to over-eat. (This certainly describes me!)
On the other hand, if you KNOW that your next meal is going to be a plain baked potato, the dynamic will change and you are more likely to eat an appropriate amount. Even if there are 6 potatoes lined up, the first one is a lot less likely to “taste like more.”
I agree, the no fats for two weeks sounds bad but he apparently did it under supervision.
I could imagine that if he was just eating potatoes for two weeks and then started eating other vegetables, those other vegetables would be the most delicious things he ever tasted. Maybe it is a good way to get yourself to eat more vegetables and less junk food if that’s your issue.
Also, it’s impressive that he lost 100 pounds, but it will be more impressive if he keeps that off, that is really the hard part.
Losing weight is not a magic trick. Eat fewer calories and you’re definitely going to drop weight. Keeping it off is the trick. One year is just not enough time to judge whether Penn will keep this weight off or just gain it all back again. Mike Huckabee (to take just one example) also reacted to a health scare by losing 100 pounds back in 2003, and then wrote a book about it. Today he certainly appears to have gained it all back.
I’ll make a note to check this thread in 2026 to see if Penn is still on track.
This isn’t necessarily true.
What a lot of people find when they reduce their food intake is their metabolism just adjusts to the new level of calories it’s receiving. They cut they calorie intake by twenty percent and don’t lose a pound of weight.
Yeah, I’ve heard this a lot, but never have seen a cite that supports it.
Studies have found that people tend to way under-estimate the number of calories they are eating.
I suppose that there may be some metabolic efficiency changes at play, but the principle of CI/CO is sound.
What I want to know is how he got himself stranded on Mars.
Just a guess, but I would think the key words here are, “Under medical supervision”.
He did it by eating 1,000 calories a day for a month. A guy Jillette’s size probably needs 4,000 calories a day to function, so he was running a 3,000+ deficit each day.
Had he eaten 1,000 calories a day in skittles instead of potatoes he would’ve lost roughly the same weight.
I have no idea about why potatoes are any good. I think potatoes are a food you can live off of because they provide many of the vitamins and macronutrients you need.
What is important is will he keep it off. People lose weight all the time, very few keep it off. If he keeps it off, that’ll be the bigger accomplishment.
Still holds true even with reduced metabolism. Assume 2000 cal a day metabolism prior to starting diet. Dropping intake to 1500 cal a day gives about a pound a week weight loss. Metabolism adjusts(you say it does, I don’t) now with a 25% reduction in metabolism base is 1500 cal a day need so dieter just reduces below that amount and still loses weight. If the body truly kept adjusting we’d get to the point of not needing to eat and still not lose weight.
When nutritionists studied which foods make you feel full for the longest, potatoes scored at the top of that list, so I suspect that had a lot to do with his choice.
Here’s the original paper published on the subject: A satiety index of common foods - PubMed
You can Google it for more lists and descriptions, but I note that almost everything is trying to sell snake oil, so I’ll stick with the scholarly link.