This is quite an old study, published in 1962, and it's in rats who are known to have greater DNL in adipose tissue. This was a fairly short study, wherein rats were put on a 2 hr/day ad libitum eating schedule for one week. Intake was 60% lower on day 1, but back up to 95% of normal ad libitum intake by the second day. Thus the rats lost weight early on, but were back within 10% of their start weight by week's end.
Essentially it appears that in short order with a switch to such a regime, adipose tissue storage and DNL in adipose tissue is upregulated considerably (10 fold). Normally a 24 hr fasted rat will have depleted glycogen stores as some is burned along with fatty acids. Rats adapted to this regime had full liver glycogen after the 24 hr fast indicating that they likely use fats preferentially for fuel.
Interesting ... not sure what it means in humans. But if something similar occurs, it could explain the insulin resistance many IF'ers seem to have, as non-oxidative glucose disposal -- e.g. glycogen synthesis -- is a major route of glucose disposal that is "defective" in IR states when reserves are high. Especially with LC, if glycogen is spared and glycogenolysis doesn't provide blood glucose, gluconeogenesis would be upregulated. The combo with hepatic IR may well be the reason why IF'ers often have quite high fasting blood glucose.
