Fasting for a week:
- Causes significant changes in protein levels across various organs.
- May have health benefits beyond weight loss, but only after 3 days.
- Switches energy source from glucose to fat after 2-3 days.
- Average weight loss of 5.7 kg (fat and muscle), with most fat loss sustained after 3 days of eating.
Implications:
- Provides insights into the molecular basis of fasting's health effects.
- Paves the way for developing alternative treatments based on fasting benefits.
- Confirms historical use of fasting for specific health conditions.
My understanding is that severe shifts in calorie intake vs output can lead to lasting metabolic changes. I think the main example people point to is that all "biggest loser" contestants failed to keep their weight down even when they maintained their diets and exercise for a long period.
It's not really metabolic per se, but hormonal. Hunger is hormone driven. If you restrict calories, you recalibrate your hormonal response to fullness and hunger.
No, these studies indicated metabolic changes: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4989512/