I Ate Nothing but Potatoes for a Week

After reading about people losing weight on an all-potato—the exact opposite of the keto diet I knew and loved—I wanted to try it myself.

I previously lost quite a lot of weight on a ketogenic diet, combined with time-restricted feeding. But over the past year, the disruption to my routine that came from changing jobs led me down a path of getting lazy with food. I began eating all kinds of junk at all hours again. And before I knew it, I'd regained nearly everything I lost. I've been disappointed in myself, and I was ready to get serious about my diet again.

Then, I read this.

Tl;dr, we’re looking for people to volunteer to eat nothing but potatoes (and a small amount of oil & seasoning) for at least four weeks, and to share their data so we can do an analysis. You can sign up below.

I was immediately intrigued. I knew decently well how keto had helped me lose weight. But potatoes? An all-potato diet is the opposite of keto! It should spike my blood sugar and insulin and make weight loss difficult. How could people find it successful?

It didn't make sense to me, which also made it very attractive. I'm a weirdo who does weird things, and this was just the sort of weird thing that I would try just to figure it out. But with a cruise trip, two birthdays of close family, and the Fourth of July coming up, I was in no position to join the trials. Four weeks is a long time! Though I missed out on joining the Slime Mold Time Mold experiment, I still wanted to give it a shot and see how it affected me. And now that I don't have so many excuses to binge delicious food, gave the potato diet a try for a week and see what would happen.

The One-Week Experiment

I committed myself to eating only potatoes (plus any necessary supplements) for one week. I also decided to try to minimize oil and salt, as some people theorized the benefit of the potato diet was from "resetting" your tastes with a bland food.

Rough Beginnings

I started on a Sunday. I prepared 5 pounds of russet potatoes and five pounds of yellow potatoes, separately, by steaming them. I think very roughly mashed them with the skins still on. No oil, no salt, no condiments. Just potato.

It was disgusting.

Less than a day into it, and I was hating this decision. I was revolted by the thought of having to eat more potatoes. By day two, I started adding salt and other zero-calorie seasonings like hot sauce. It helped a little with flavor, but I was still not enjoying it.

I also started experiencing gastric distress. I'd read the accounts of other potato dieters that eating the skins could cause this—too many toxins in them that, which when consumed in the volume I was eating, could cause nausea. I was lazy and had not peeled my potatoes, to my own detriment.

I seriously considered giving up by day three. My daily caloric intake was around 1,000 calories. Eating more potato than that was unthinkable. I was craving anything but potato. I had done multiple 72+ hour fasts that were mentally and physically easier than the potato diet!

Laziness to the Rescue

I resisted the temptation to give up. But I knew I had to change what I was eating. I swapped out my plain mashed potatoes, and bought some frozen fries and tater tots from the local grocery store. Because I was so late starting, I had the benefit of seeing how earlier potato dieters had done. And I knew that others trying this diet had gone a similar route with perfectly fine results. I thought, if this doesn't work, I'll definitely give up.

And to my great relief, it worked wonderfully!

The fries and tots were much tastier, thanks to some (admittedly crappy seed-based) oil and salt. And they had other advantages too. I could get a 2 pound bag of either for just $1.65. It took only 12 minutes to cook them in my air fryer. And the lack of skins meant my gastric distress went away!

So from day 3 onward, I mostly ate frozen fries and tots. Sometimes I made sweet potato fries from scratch, but never more than once a day.

Breakdown of calories consumed during my week of potatoes. Very low to begin with, but goes up as I introduced frozen potato foods with oils in them.

Results

Weight Loss

By the end of the experiment, I had lost 1.8 pounds. That's a decent bit of weight loss in a single week. But, I also regularly see swings of that size day-to-day. My weight during the experiment didn't trend monotonically downward, and I can't rule out that my weight loss was coincidental. I don't think one week is enough time to evaluate if a potato diet would help me lose weight.

Weight and net calories for the past two weeks. For the prior week, net calories are around 0 and weight is stable. During the diet, net calories drops by about 1,000 per day and weight starts going down erratically.

Nutrition

I didn't realize how high in potassium potatoes are. During the experiment, I averaged over 5g of potassium per day! That's about double what I averaged the week before, when I wasn't trying any diet in particular. I was also surprised to see that my omega-3 needs were well met by potatoes, though I'm sure that was ALA and not DHA or EPA.

Other nutrients were quite low, including calcium, choline, vitamin D, vitamin K, iodine, and selenium.1 I would have been very low on B vitamins too if not for supplements. And protein was unbelievably low, averaging 25g per day versus 140g per day in the prior week. I'm amazed how much energy I still had, given how little protein was in my diet and how much that's affected my energy levels in the past.

Click here to see full micronutrient daily averages.

These tables contain the daily average micronutrient consumption (i.e., vitamins and minerals) from my week eating potatoes (plus some supplements), from the week previous (a Standard American Diet™), and from the following week eating a keto. Data comes from weighing food and logging it in the Cronometer app. How useful this data is aside from the potato numbers is questionable, since there are so many ways to eat SAD or keto and mine are unique to my time and place. And whether or not I take supplements (sporadically done during potato diet, not at all on the others) also greatly affects these values.

Daily Average Nutrients on Different Diets
Nutrient Potato Diet Standard American Diet (Previous Week) Keto Diet (Following Week)
B1 (Thiamine) 2.6mg (220%) 1.4mg (114%) 0.6mg (52%)
B2 (Riboflavin) 1.9mg (143%) 1.5mg (116%) 1.1mg (88%)
B3 (Niacin) 26.3mg (164%) 20.1mg (126%) 15.2mg (95%)
B5 (Pantothenic Acid) 9.8mg (197%) 3.4mg (69%) 3.6mg (73%)
B6 (Pyridoxine) 4.1mg (316%) 1.5mg (114%) 1.2mg (94%)
B12 (Cobalamin) 6.5µg (269%) 6.2µg (260%) 4.7µg (194%)
Choline 219.6mg (40%) 352.3mg (64%) 351.3mg (64%)
Folate 368.8µg (92%) 147.2µg (37%) 109.9µg (27%)
Vitamin A 1676.9µg (186%) 436.9µg (49%) 350.9µg (39%)
Vitamin C 130.7mg (65%) 14.5mg (7%) 27.2mg (14%)
Vitamin D 171.7IU (29%) 366.5IU (61%) 417.3IU (70%)
Vitamin E 9.8mg (65%) 3.5mg (23%) 6.1mg (41%)
Vitamin K 53.7µg (45%) 135.2µg (113%) 88.0µg (73%)
Calcium 244.3mg (24%) 976.3mg (98%) 839.8mg (84%)
Chromium 25.7µg (73%) 0.0µg (0%) 10.5µg (30%)
Copper 1.6mg (182%) 0.5mg (53%) 0.7mg (80%)
Iodine 34.4µg (23%) 64.6µg (43%) 76.2µg (51%)
Iron 9.6mg (120%) 14.0mg (175%) 8.3mg (104%)
Magnesium 308.2mg (73%) 189.2mg (45%) 238.8mg (57%)
Manganese 3.1mg (135%) 0.8mg (35%) 1.0mg (41%)
Phosphorus 803.7mg (115%) 1096.1mg (157%) 1024.4mg (146%)
Potassium 5278.3mg (155%) 2642.4mg (78%) 1800.3mg (53%)
Selenium 20.6µg (37%) 121.3µg (221%) 81.3µg (148%)
Sodium 2697.7mg (180%) 2501.5mg (167%) 1920.7mg (128%)
Zinc 11.1mg (101%) 15.2mg (138%) 10.7mg (97%)

How It Feels to Only Eat Potato

The frozen potato foods were really quite filling. I largely didn't think about other foods during this period. A big plate of fries or tots left me sated. My net calorie intake went down by about 1,000 per day without me feeling like I was depriving myself.2 I rarely felt hungry or experienced cravings.

I don't think my tastes were "reset" by the blandness of potato. When I was eating the blandest mashed potatoes, I craved other foods the most. When I switched to tastier fries and tots, cravings went away.

But the feeling of eating only potatoes is not perfect. I don't think my guts are big fans of potato in general. Despite my earlier gastric distress going away after removing skins from the diet, I still feel a bit off. I'm not used to a general level of digestive discomfort, either on keto or the Standard American Diet™.

Click here to read about potato poops. 🥔💩

I think potato has trouble moving through my bowels. I got cramps, like my body is trying very hard to move things along. I never had these problems on a keto diet.

Everything came out OK. The experience of pooping was fairly normal. The poop itself was strange, though. It just seemed to start dissolving into the toilet water almost immediately. So I would have the physical sensation of a normal poop, only to turn around and see what looked more like diarrhea.

I'm sure you're glad you clicked to read that!

Ending the Potato Diet

I guess this experiment is a success? I did lose weight, after all. But the digestive distress I've experienced doesn't seem worth it. My body just isn't a fan of only eating potatoes.

I went one extra day, but decided it was time to end it. I just didn't feel right. Low grade nausea and feelings of bloating. Thinking I would go back to keto, I made myself some cheeseburgers (with keto buns) and enjoyed them.

However, by that evening, I started feeling a highly localized intermittent pain in the upper-right quadrant of my abdomen. I tried to sleep it off, but it woke me up during the night. Very specific in location and presentation behind the ribcage.

This is hardly the first time I've dealt with mysterious abdominal pain—I've had different ones on and off for years without resolution or even diagnosis. Regardless, it seemed prudent to consult a doctor. They ran some blood tests to look for signs of elevated liver or gallbladder enzymes, but everything came back normal. I'm still experiencing the pain on-and-off, though not as often. Just like in years past, I have no explanation. I also don't know how/if the pain's emergence is related to the potato diet and my sudden reversal, going from high-carb low-fat to low-carb high-fat. I don't have data to suggest anything either way.

Since stopping my potato diet, I've gone back to a stricter keto diet than what I was eating previously and weight loss has continued. While I miss the simplicity of "buy frozen tots, throw in air fryer", I generally feel better this way.

You can see the make up of calories in this chart from the potato diet, which was very high carb, and the switch to keto afterward, which is much higher fat and protein with little carbohydrate. Weight has continued to trend down with no observable difference between the potato diet and keto diet.
  1. And that's after taking a multivitamin most days! ↩︎

  2. First few days of bland mashed potatoes excluded. ↩︎