Reddit reviews Biochemistry (4th edition)

I'm assuming this slide (and the discussion thereof) is your source

The presenter does state that it takes them to get back into ketosis following a Cyclic Ketogenic Diet while at a caloric deficit while doing interval training 5 days per week. So, not super applicable to the general population.

In case you're unaware, CKD includes a massive carb up over the weekend. Per Lyle McDonald (literally the guy who wrote the book on CKD), in the carb up phase,

>8-10 grams of carbohydrates per kilogram of lean body mass should be consumed during the initial 24 hours of the carb-load. This will make up 70% of the total calories consumed. During the second 24 hours, approximately 5 grams/kg should be consumed which will be approximately 60% of the total calories consumed.

For a person of 160 lbs, that works out to 725g 630g of carbohydrates the first day, and 363g 310g of carbohydrates the second day. Unless you're specifically doing CKD, it's not very likely to encounter this "in the wild" so to speak, and therefore it's difficult to make an argument for generalizing this one specific data point to an entire population.

Another critique: The goalpost he picks for being in ketosis or not is 0.3mMOL. AFAIK, there is no specific definition for being in ketosis or not. Wikipedia, for example, cites Volek and Phinney as 0.2mMOL as the cutoff point where slight/mild ketosis begins. Per that metric, the data points show the subjects reentering ketosis on Tuesday, if not Monday.

---

Later on, the presenter brings up this slide (21:42). These were athletes who were not adapted to keto that were split in to two groups. The group on the left continued with their traditional resistance exercises. The group on the right were additionally required to perform intense intervals to test if it had an effect on fat metabolism. He had already stated a few moments earlier that it did.

That extra information is beside the point though, both groups easily exceed 0.3mMOL blood ketone levels on Tuesday, and I'd hazard a guess that they both had exceeded 0.2mMOL blood ketone levels on Monday.

---

Finally, let's consider how much carbohydrate is able to be stored by your body (but not as fat).

Per this article,

> Glycogen storage capacity in man is approximately 15 g/kg body weight and can accommodate a gain of approximately 500 g before net lipid synthesis contributes to increasing body fat mass. When the glycogen stores are saturated, massive intakes of carbohydrate are disposed of by high carbohydrate-oxidation rates and substantial de novo lipid synthesis (150 g lipid/d using approximately 475 g CHO/d) without postabsorptive hyperglycemia.

Only about 100-120g of the ~500g is stored in the liver and is therefore available to the rest of your body. The remainder of glycogen is primarily stored in muscle tissue and other organs, which are unable to release it back into the blood stream.

Citing this biochemistry textbook (really any one should do), on this page, good ol' Wikipedia states,

> The 100 g or so of glycogen stored in the liver is depleted within one day of starvation. Thereafter the glucose that is released into the blood by the liver for general use by the body tissues, has to be synthesized from the glucogenic amino acids and a few other gluconeogenic substrates, which do not include fatty acids.

In effect, after one day of starvation, (true starvation or physiologically equivalence like keto), the liver runs out of glycogen and must start synthesizing glucose from amino acids (or other gluconeogenic precursors) via GNG.

EDIT: Minor rewording in order to flow better.

EDIT II: Corrected numbers to account for 140lbs LBM instead of total body mass.

EDIT the third: Clarified GNG process.