That's actually different, you're talking about calorie restriction (-50% of needs), what we've been discussing is fasting (0% of needs). There are substantial physiological differences between the two modes, and that study is not relevant to this conversation. Fasting actually improves your body composition (reduces proportion of fat : muscle) [5]. Further, even if you regain all the weight you lost, you'll still have a better body composition after fasting vs. CR [6].
Speculatively, even the reduced amount of food will suppress HGH production - while total abstention yields many hundreds of percent increase in levels [3, 4]. HGH is known to be responsible conserving muscle and improving body composition.
It's been shown in studies that fasting raises your metabolic rate [1, 2] (again, offer not applicable to CR, by your own study and some others I don't have on hand right now). This is likely due at least in part to the production of norepinephrine during fasting. This further substantiates my point that we're talking about two different modes of operation.
CR != Fasting.
FWIW I agree with you, reducing your calorie consumption 50% but maintaining your 3-a-day plus snacks eating schedule is not great for you ("starvation") and likely damn hard to stick to. Weight Watchers themselves published a study that showed it just doesn't work. [7] This is what they were testing during the Minnesota starvation experiment and that didn't go well, to say the least. What my review of numerous studies indicates, is that the relationship does not extend to reducing your caloric intake 100% (obviously, intermittently for some value of intermittent). What it appears is being re-discovered is that it's not how much you eat, but what you eat, and how when/how often.
I specifically commented on someone saying “our ancestors would just die of starvation”. So, if you want to talk about short term fasting then that’s cool but really not related to this thread of conversation.
Anyway, I agree under 2 weeks of fasting is not starvation. The body does not go into starvation mode over a few days becase it’s extremely expensive to cycle building up and removing skeletal muscle.
PS: It generally takes 24 to 72 hours for food to move through your digestive tract. In the very short term fasting you get excess energy because digestion takes energy. But extend that for 3+ weeks and very different things start happening.
My reading implies that the number of muscle cells does not change and that protein in the muscles is rapidly rebuilt upon re-feeding.
Entering 'starvation mode' from studies appears to happen around day 3-5 of fasting, there's charts in the links I provided. That's when the new energy distribution is in full effect and the brain is deriving most of its required energy from ketone bodies. If you have some interesting stuff to read about another shift that happens around 2 weeks I'd love to check it out, I'm always looking to learn more about this stuff. When 'starvation mode' switches to dying mode appears to be when all your fat stores are exhausted and the body no longer has fat to consume for energy. If you're obese that can be 12 months away or more. Most people who fast for long periods note the switchover happens when their breath turns sweet and a real feeling of hunger returns -- that's obviously when they break the fast so as not to die.
Speculatively, even the reduced amount of food will suppress HGH production - while total abstention yields many hundreds of percent increase in levels [3, 4]. HGH is known to be responsible conserving muscle and improving body composition.
It's been shown in studies that fasting raises your metabolic rate [1, 2] (again, offer not applicable to CR, by your own study and some others I don't have on hand right now). This is likely due at least in part to the production of norepinephrine during fasting. This further substantiates my point that we're talking about two different modes of operation.
CR != Fasting.
FWIW I agree with you, reducing your calorie consumption 50% but maintaining your 3-a-day plus snacks eating schedule is not great for you ("starvation") and likely damn hard to stick to. Weight Watchers themselves published a study that showed it just doesn't work. [7] This is what they were testing during the Minnesota starvation experiment and that didn't go well, to say the least. What my review of numerous studies indicates, is that the relationship does not extend to reducing your caloric intake 100% (obviously, intermittently for some value of intermittent). What it appears is being re-discovered is that it's not how much you eat, but what you eat, and how when/how often.
[1] https://www.ncbi.nlm.nih.gov/pubmed/14066725
[2] https://www.ncbi.nlm.nih.gov/pubmed/10837292
[3] https://www.ncbi.nlm.nih.gov/pubmed/3127426
[4] https://www.ncbi.nlm.nih.gov/pubmed/1548337
[5] https://www.ncbi.nlm.nih.gov/pubmed/17413096
[6] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5042570/
[7] https://fatfu.wordpress.com/2008/01/24/weight-watchers/