My experience With the Atkins Fat Fast

Several years ago when I was losing weight, I decided to try the famous “Atkins Fat Fast” to break a stubborn stall. Okay maybe it wasn’t that stubborn – maybe I was just a wee bit impatient to drop those final few pounds;-)

For those who’ve never heard of the Atkins Fat Fast or don’t know much about it, a Fat Fast is basically a short-term way of eating, which involves eating a diet as close to 100% fat as possible for a few days.  It’s promoted as being useful for breaking a weight loss stall or for kick starting weight loss in those who are very metabolically resistant to losing weight. In his practice, Atkins noticed that there were some people who were so metabolically damaged, that even when eating a LCHF diet of 20 net g carbs or less, just couldn’t lose weight. He studied these patients and discovered that imposing a Fat Fast for a few days was an effective way for such people to start losing weight. His aim was to demonstrate that weight loss, while more difficult for those who were very insulin resistant, was not impossible. From his findings he concluded that, as this approach worked, then simply increasing the amount of fat in ones diet, while keeping carbs extra low and protein at moderate levels, might also get the job done.

The Fat Fast consists of 5 daily “feedings” of approximately 200 calories of fatty food per feeding for a total of 1000 calories a day. Atkins emphasized that the Fat Fast should not be done for more than 5 consecutive days and used it on patients for 3-5 days at a time.  Unlike, Atkins’ general advice of “eat all you want and just count carbs”, the Fat Fast is a calorie, carb and protein restricted approach where one eats a very narrow range of fat-based foods for a relatively short period of time.

Authors who write about the Fat Fast are very careful to warn that you shouldn’t do the Fat Fast without medical supervision, and that the Fat Fast should be used as a last resort when every other approach to losing weight via diet has failed. Therefore, please understand that I am in no way promoting or endorsing the Fat Fast but… however I know that a few of you are curious about it so I’ll share my personal experiences with you.

Before I tried the Fat Fast, I avidly searched the internet for real life data about how much weight one could lose by doing the Fat Fast, whether that weight loss would be permanent or  the weight would return as soon as one began to eat a regular LCHF diet again, and what kind of things people enjoyed eating during their Fat Fast. Now, as someone who loves reading nitty gritty details and stories of peoples first hand experiences, I was quite disappointed to find that there were very few detailed accounts of peoples experience with the Fat Fast and even less data about how much weight they lost. A few bloggers had started posting Days 1-2 of their Fat Fast and then seemed to have abandoned the project. Hmmmm.

So… what did I eat?

I ate alot of cream cheese (measured out into 200 calorie allotments, of course), mascarpone sweetened with powdered erythritol, mushrooms cooked in butter and cream cheese or boursin cheese, small scoops of tuna salad made with extra mayonnaise. I drank Bullet Proof coffee and ate many, many feedings of macadamia nuts (one of the most palatable of all the feedings).  Perusing Dana Carpender’s Fat Fast recipe book, I found a recipe for Shirataki noodles in a cream sauce which I thought looked and sounded delicious. Little did I know that shirataki contain ‘glucomannan’, which can have an alarming laxative effect on some people. I know that many people love shirataki, however due to the extreme effect they had on me, and their awful taste and smell (they literally made me gag),  I will NEVER eat shirataki ever again. I would view having to eat shirataki as a form of torture.  For the 3 days that I was on the Fat Fast I continued to track my foods in FitDay and averaged about 6-7g net carbs each day. My daily protein intake averaged around 15g-20g and my % of fat hovered at around 90-92%.

How did I feel?

Mostly just fine, physically. Given that I was already in ketosis and fat-adapted and very familiar with the low-carb way of eating, I didn’t experience much hunger at all. I definitely would not recommend going from high carb eating directly to a Fat Fast.  I imagine that would be quite a shock to your body. For me, the calorie drop to 1000 calories was not that severe given that I had been averaging around 1300-1400 calories daily (I’m only 5 feet 2″ and was in my mid 40’s at the time). I did feel very, very bored with the food choices and really missed eating salad and proteins. Sometimes I felt a little light headed, however generally I felt very calm both emotionally and mentally. My plan was to do the Fat Fast for 5 days but after only 3 days, I was thoroughly sick of eating this way. On the evening of the third day of my fast, I recall feeling very excited knowing that I would be returning to my regular LCHF diet the next day. There was also too much counting and balancing of food – even for me. Anyone who knows me knows that I’m someone who doesn’t shy away from details, yet I grew tired of doing endless math and struggling to consume at least 90% of my calories as fat. Eating at 90% fat rules out alot of food combinations that are perfectly fine on LCHF. Eating LCHF is a breeze compared to doing the Fat Fast.

How much weight did I lose?

In 3 days of fat fasting I lost a total of 3.7 pounds – not too shabby. I broke my stall and furthermore, I continued to lose weight for the next week by deliberately keeping my percentage of daily fat higher than my usual intake (around 75% – 80%) and my protein at around 50g a day. Being able to eat my usual LCHF diet again felt like feasting compared to my limited choices during the Fat Fast. I had a new appreciation of food in those first few days following my fast and felt so lucky to be able to enjoy meat and veggies again – such luxury!


I found the Fat Fast to be effective but wearing psychologically and very boring due to the limited food choices. It did teach me that by generally increasing the fat content of my diet and lowering my protein intake I could break a stall. However,  a less extreme approach to the one recommended by the traditional Atkins Fat Fast would be less arduous, and still effective, at least for me. Would I use this method again? Unlikely as I missed eating real food. I would favor simply increasing fat and lowering protein slightly, intermittent fasting and even slightly lowering calories/increasing exercise to doing the Fat Fast. AND – I never want to see a plate of pan-fried mushrooms with melted boursin cheese or a bowl of shirataki noodles ever again!

What has your experience been?



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