Low testosterone. I recently had to deal with the same issue. In my case, too much protein I suspect that was his problem as well, too lean a diet with too high protein. Insulin signalling will help, as will replacing some protein with carbs. He feels great, wish I did not have IR or I might eat more carbs myself, but I do have IR, so I will not be following him.
Oh yah, I went carnivore from keto due to IBS-D
I was gaining on carnivore, it was only 2kg mind, but my clothes let me feel the slight difference. I was up to 54kg (I am 5.2) I added back in just a few carbs (vegetables and nuts) whilst staying below the 20 reccommended grams for keto, and I have lost the 2kg I gained, so Iām back down to 52kg. Itās highly individual how this works, and one solution definitely does not fit all.
And I do wonder if there is something to Dr. Paul Saladinoās claim that carnivore is not a ketogenic WOE, as perhaps the high protein amounts people are reccommended to eat kicks them out of ketosis. The other thing, as has been seen in extended fasting also, and calorie restriction (so might work the same way with carb restriction?) is that the body can down regulate metabolism, can also (possibly?) begin to produce glycose because of lack of carbs. There are individual factors involved and so many variables.
My dietary focus is keeping carbs low while meeting all scientifically derived vitamin and mineral requirements (using Cronometer). I have found no way to do this without eating plants. (I will never eat organ meatsā¦) Iāve seen claims that people in ketosis donāt have the same requirements but Iāve never seen anyone post scientific evidence to back that up ā just anecdotes.
I searched for evidence on vitamin C in the Inuit diet and found their need was not so different:
The one that is documented is Vitamin C. Eric Verdin has shown that elevated insulin activates a gene complex that inhibits the bodyās endogenous defences against oxidation, and the Ī²-hydroxybutyrate produced on a ketogenic diet deactivates those genes, thus restoring the bodyās endogenous anti-oxidant defences, and greatly reducing, if not eliminating, the need for exogenous anti-oxidants. So
Ī²-hydroxybutyrate has epigenetic effects, as well as providing fuel.
Fresh meat has been known for centuries to prevent scurvy. The problem the British Navy faced was that it was impossible to stock enough livestock to provide their sailors with fresh meat on long deployments, so they settled on Vitamin C from lemons and limes, instead. It was simply much easier to stock citrus than to provide fresh meat. (Once the livestock were all eaten, the sailorsā diet became shipās biscuit and salted beef.)
But you are right that the rest of the speculation is not documented. However, physicians who treat low-carb/keto patients notice lower thyroid values, but no symptoms of hypothyroidism, so there is a growing body of case studies to show that the body may use thyroid hormones more efficiently, without insulin to interfere.
I guess I would ask, what is meant by āfresh meatā (maybe itās raw, as the Inuits often eat it), and who is eating it now? The paper I cited found borderline scurvy in some Inuits. My point is that even inuits in ketosis seem to need sufficient vitamin C which many of us today probably canāt get from meat alone.
āFresh meatā is meat that has been recently killed before cooking, but that has not been preserved in any way, other than by refrigeration or freezing. For example, the diet that Stefansson and Andersen were on, during that year in Bellevue Hospital, and Stefansson for the rest of his life. I suppose it could be eaten raw, but that raises the possibility of other health problems.
Why would be carnivore non-ketogenic while keto with the same amount of protein and possibly more carbs ketogenic then?
People eat more or less protein both on keto and carnivoreā¦ Why would I start to eat more protein if I abandon plants? 
(Though yep, vegs brought a ton of fat into my lifeā¦ But I need that fat anyway so now meat brings it, among others.) More like less as I manage with a tad less foodā¦ I met carnivores eating <60g protein and there are normal ketoers eating 2-300gā¦ Itās not about the plants at all.
There is the super fatty version of carnivore tooā¦
Whenever I used Cronometer, it told me I am horribly low at something and I saw no way to change it even eating 40g net carbs a day so I just ignore it 
My body doesnāt complain, Cronometer clearly has no idea about my own individual need on my individual dietā¦ Of course, everyone should do their best according to their attitude. I donāt even see a better option than what I have, my body just not into sugars so vegs are pretty much out.
I have read the inuit thing with the algae. The same article talked about them being borderline Vitamin C deficientā¦
IDK if itās true and we eat differently anyway, I just do what I can and if I get scurvy, I will notice Never managed it yet. But if it will happen, I will just supplement with Vitamin C (or use more lemon, I like lemon and itās perfectly fine on my own carnivore-ish). I donāt eat any food if I donāt want them.
But if we cook it into oblivion, it still loses more and more Vitamin Cā¦ So itās an uncertain feeling to think about vitamin C from meat when we only eat it well-cooked. Okay, there is a few dish where I only use 30 minutes but thatās it, I donāt eat any meat cooked for a shorter time. (My little raw meat has no Vitamin C as itās smoked. Sigh.)
I have exactly zero info about what Vitamin C does, I just know it starts to disappear at a lowish temp, longer time is worse and I forgot about the temp where it simply becomes zero but thatās very high.
SOME probably stays but how much? No idea. And if more has some benefit on carnivoreā¦
But as I never faced an obvious problem regarding Vitamin C, I just use my normal attitude and donāt worry about it. There are just too many things to think about, it would damage my mental health.
That was Paulās solution (if I am even correct that too much protein (think above 3.5g/kg) was the cause for him as well as me). I adjusted my fat content up and seem to have fixed my testosterone (not re-measured in lab, but with performance). I am sure carbs would spike insulin without the protein being as high and resolve as well. So hard to confirm for Paul from a distance, but he has stated openly that adding in carbs spiked his insulin and afterwards his testosterone has gone way up. My thoughts are that he also lowered protein intake to compensate and thereby resolved in a similar way to me.
You would cook your meat āinto oblivionā? I wouldnāt; I want to enjoy my meals, lol!
Shinita, I am not entirely sure as to the science behind Dr. Paul Saladino claiming the carnivore WOE is not ketogenic. But he has expressed that he thinks this is a good thing, sharing his concerns about remaining in ketosis indefinitely. In terms of the carnivore WOE ceasing to be ketogenic, it may be a matter of the 0 carb allowance eliciting a response from the body, causing it to produce more glucose, and at the same time the body might down regulate metabolism. There may be other mechanisms involved that I donāt know of, Dr. Paul Saladino has been talking about the high protein intake on carnivore stimulating mTor, the growth hormone, but Iām not sure that has anything to do with it. I have to confess I donāt really understand the science behind Dr. Paul Saladinoās claim. When I am next on a computer Iāll share the link to his video.
My own experience was that when I added back just a few carbs (whilst staying well below the keto carb limit) I lost the 2 kg I gained on carnivore. And I am enjoying vegetables again, though only in small quantities. I never did have a carb addiction, so I can eat a strawberry say, and leave it at that. A small handful raspberries, or a small amount of almonds (which I have with my morning coffee along with a couple slices of cheese, thatās my breakfast). But it is all so individual, what works.
@PaulL: Thatās why I cook them for 1-3 hours 
I am a hedonist, of course I will make them into a tasty crisp I prefer (or soft tenderness if itās cooking in the stricter sense)! (Okay, not always. I only use 30-60 minutes for liver and other fried stuff.)
Itās not charcoal so itās good but I doubt it has a lot of Vitamin C left at that pointā¦
What about carnivore with 20g carbs then? Or animal sugar is special even regarding this?
Carnivore has no special carb or protein intake, it can be exactly like a normal keto macro wiseā¦
Oh well, itās not like I ever cared about ketosis except in the first 7 weeks as I wanted fat adaptation. I ate high protein then tooā¦ I just donāt understand it and it very very slightly bothers/interests me sometimes.