Why do I react funny to lean protein if eaten alone?


Hey guys,
I’m new, so hello everybody. Sorry I’m asking this question but so far, no amount of googling could help me on this. Sorry in case I posted to the wrong sub forum.
I’m doing Keto for 14 weeks now and so far, I’m very happy. However, sometimes I have a really bad reaction after eating. It’s like a total energy crash, with feeling extremely fatigued, tired, cold (shivering) and it’s impossible to think straight (brain fog deluxe). It only happens when I’m eating lean protein as a snack but never when I do OMAD (where I usually get all my protein + fats in one meal).

I had it happen to me after eating a can of tuna, or 100g of corned beef, or whey protein, or trout. Never with cheese. The thing is, I can eat all these things during my OMAD and it’s all good. My husband can eat 2 cans of tuna in one go and doesn’t notice anything, if I eat 2 cans of tuna without any added fat I’ll be ill for 6 hours. But when I make a tuna salad with mayonnaise and eggs, I can eat an equal amount and I’m fine.

It’s actually not such a big deal, I just noticed I can’t eat any lean proteins without any fat, but I’m really curious why this happens to me and probably nobody else as I haven’t read about it so far?
I suspected some type of allergy, but I can eat the exact same foods together with fat and it’s fine. It also doesn’t give me any digestion issues, so no general protein intolerance. I do KNOW it’s not “too much protein is kicking me out of Ketosis”, and I also don’t think it’s an insulin issue as it would happen with any big amount of protein, no matter if I added fats or not, right?

Still, I’m just curious what the science behind this is, if there is any. Maybe it’s just a weird individual specific thing.

Thanks in advance for reading and kind regards!


Have you tested your blood sugar when this happens? It sounds like it could possibly be hypoglycemia.

(Bacon by any other name would taste just as great.) #3

It’s because we need fat as well as protein in our diet. In the famous experiment on Stefansson and Andersen, they were persuaded at one point to eat lean meat and felt terrible. A little fat perked them right up. Is there any reason you can’t include fat in your snacks?


Have you tested your blood sugar when this happens? It sounds like it could possibly be hypoglycemia.

Yes, I have, and blood glucose was 91 around 2 hours after eating it.

It’s because we need fat as well as protein in our diet. In the famous experiment on Stefansson and Andersen, they were persuaded at one point to eat lean meat and felt terrible. A little fat perked them right up. Is there any reason you can’t include fat in your snacks?

I’ll have a look at this experiment. There is no specific reasons, it’s more that I’m unexpectedly hungry, looking for a quick fix and then grabbing a can of tuna or corned beef, or have a protein shake. As my husband can eat all the protein and has no problems, I have been wondering why it knocks me straight out of my shoes.

(Bacon by any other name would taste just as great.) #5

Everyone’s metabolism is different, for one thing. For another, if you need calories, you need to eat fat. Protein is highly inefficient to metabolise for energy, and the body prefers to use it for structural purposes. You get much more energy per molecule out of fat, not to mention that fat has twice as many calories per gram as protein, and without the insulin effect, either. All this makes fat the best source for energy. Listen to one of the videos of Dr. Phinney’s workshop on practical tips for eating a ketogenic diet. Fat hunger is a real phenomenon.

(Edith) #6

I tried a carnivore diet for a while. There were a few times that I ate too much protein, particularly for lunch, and felt drugged afterwards. I think my body reacted to the too much protein the same way it reacts to too much carb.

(Bob M) #7

You might want to test every 30 minutes for both a normal meal and a high protein meal. Or even more often. This is from Thanksgiving 2017:

The time between the lines is 1 hour. I had Tgiving dinner right about 1pm, very high carb, then dessert thereafter, which is what the two main bumps are. Note that the duration of each bump is less than one hour, so If I took before eating and an hour later, I would get the same reading, and miss the 9.7 (175 in US units).

I think that perhaps you’re starving yourself. Protein is a poor energy source, and your body is looking for energy. You can’t get get that protein (and protein does not turn into sugar). So, if you up your fat even by a little, it would likely prevent this.


That is interesting, “drugged” is a good description and I can relate to that. May I ask you how much protein you were eating and do you know what exact process is causing this?

What is a high protein meal for you? I usually do OMAD where I have all my protein in one sitting together with the fat and the veggies. It’s around 90-110g of fat and 70-125g of protein. I have never reacted in a bad way to this one meal.
Yesterday, I had 50g of protein as a snack and I had a really bad response from my body. It’s less protein than usually in my OMAD, so do I have a normal or a high protein OMAD?

No worries, I am not. Like I said, I usually do OMAD and have nearly all my macros in one big meal. That’s currently around 100-110g fat, at least 70g of protein and around 20g of carbs. That should be around maintenance calories for me.
Just sometimes when I am REALLY hungry in the late morning or evening, I would want to eat a snack. And the easiest to eat has always been a can of corned beef, tuna or some smoked trout. It’s mostly a convenience thing. I wouldn’t know what else is easy to snack on, besides maybe an avocado. Before Keto, I would have eaten a banana.

(Bob M) #9

You were specifically asking about high protein low fat. That was a high carb meal.

You want a high protein meal? Here’s one:

I do not get hypo or hyperglycemia after eating high protein, low fat – ever. And I’ve eaten 200+ grams of protein in one meal. (One MEAL, not one day.)

I was trying to tell you that (1) testing at 2 hours is useless (no matter what you are eating); and (2) you might be having an issue because you don’t get enough energy from high protein, low fat.

I commonly have very low fat ham for a “snack” if I’m still hungry after dinner and after putting the kids to bed, with zero issues. However, I’m not you.

So, to reiterate, if you want to know how a high protein, low fat meal affects you, test every 15 minutes-30 minutes or get a CGM, as I did; and if that does not pan out (no blood sugar change), then it might be because you are not getting enough calories from fat. This is a new theory of mine, which has some basis in evidence from testing myself.


Can you recommend a CGM? Is that one with a needle?

(Cancer Fighting Ketovore :)) #11

I use the FreeStyle Libre, since it falls under my insurance’s “prescription” coverage (just like a medication). I was able to get it (the prescription) from my doctor without having to be diabetic, on insulin, etc. The reader was about $65 (with insurance, otherwise about $80) and each sensor is about $37 ($80 without insurance).

If you are diabetic, then perhaps the Dexcom would be a good choice. They both have a small needle/filament that gets inserted under the skin on your arm. For me, it didn’t hurt much going in (just a very slight pinch). Then the sensor will just stay on your arm (via sticky tape) for 14 days and record data.

The FreeStyle will take readings every 15 minutes, and then to see a reading you would scan the sensor with a little reader device. It does not need calibration with finger-sticks, but sometimes its good to check (like if doing a fast, or if the way you feel doesn’t match what the reader shows).

I’d be happy to talk to you about it more later. I’m currently on my 3rd sensor. You can also get all kinds of reports via the LibreLink website.

(Diane) #12

I often keep hard boiled eggs in the fridge for adding to meals or for snacking. An egg has pretty perfect keto macros.

(Edith) #13

Well… I have to admit, it was something I noted, but didn’t take data or make any notes. It happened a few times. I know it was a half pound (about 450 grams) because I freeze meat in half pound baggies. The most recent was definitely beef, beef brisket to be exact. I don’t remember what kind of meat the other times. Probably beef.

(Cheryl Bryant) #14

Wow!! I have this same issue with protein. Ive researched, googled, asked other ketoers with no luck at getting answers. I concluded it was some type of allergy or sensitivity to protein. It started with whey protein shakes, 10-15 minutes after consumption I would get extremely tired, then loopy feeling which lead to me basically passing out! If i was lucky enough to be somewhere i could sleep an hour, i would wake up and then feel fine. Soon afterward experiencing this with whey protein, i also would feel off with lean meats, pea protein(like you stated with almost all lean proteins) but i noticed if i consumed a protein with a meal it didnt bother me at all, im guessing my meals included fats. Ive been keto almost a year, started off with high fat keto then switched to more lean protein, moderate fat. Im definitely getting in enough calories, never had an issue with blood sugar(thou i dont test), take electrolytes religiously and i dont believe you can eat too much protein. Its absolutely crazy, makes no sense too me at all. Though im glad there is at least another person who is also experiencing this! Hopefully someone can adventurely shed some light on WHAT is causing THIS issue with protein and WHY???

(Bob M) #15

It might be a glucagon issue. Whey protein in particular is supposedly very insulinogenic, meaning it causes a huge insulin response. Good if you want that, say for building muscle, not so great if you don’t.

What should happen is that insulin should go up, then begin coming down. Your blood sugar should go down. When insulin starts coming down, glucagon should come up, to cause your blood sugar to be stable. That’s what happens in me.

For some people, though, their glucagon response is messed up. It doesn’t counteract the drop in insulin, meaning you should get low blood sugar and the corresponding effects of it (eg, shaky, tired, etc.).

If you could test blood sugar, that might help see what’s happening.

Note that Jimmy Moore has a similar effect to protein. Oddly, he has a similar and even worse effect to high fat (90+ % of calories).

(Bacon by any other name would taste just as great.) #16

Protein by itself is not a healthy diet. It is a good idea to eat fat as well. Under normal circumstances, the amino acids from the protein we eat are not metabolised, but rather saved for constructing new proteins (bone, muscle tissues, organ repairs, etc.). All metabolism requires a certain amount of energy, but glucose and fatty acids yield more energy from being metabolised than protein does, so the body uses protein metabolism more as an emergency backup than a regular process.

Since carbohydrate is essentially long chains of glucose molecules, and glucose in the blood is what stimulates the insulin response the most, we want to avoid eating carbohydrate to the extent possible, so as to keep our insulin low. We only need a moderate amount of protein, and it’s not a good energy source to begin with, so that makes fat an important part of our diet, since fatty acids have almost no effect on our insulin level, which makes fat a good source of calories. (Protein has something of an effect, but less so when we are on a low-carbohdyrate diet.) If all you are eating is protein without fat, it is possible that you are not getting enough energy, causing your body to shut down.