After fasting for 3 days, your body has trouble handling sugar when you eat it again, causing higher blood sugar and insulin spikes.
Scientific Claim
Prolonged fasting (72 hours) impairs glucose tolerance, resulting in higher blood glucose and insulin responses to carbohydrate intake.
Original Statement
“After the 72-hour fast, fat oxidation was higher, as you'd expect. But glucose tolerance got worse. Their blood sugar glucose spiked higher, insulin spiked higher, and glucose oxidation dropped. And this is the body going, I've been running on fat for a few days. I'm not switching gears very easily over here.”
Context Details
Domain
nutrition
Population
human
Subject
prolonged fasting (72 hours)
Action
impairs
Target
glucose tolerance resulting in higher blood glucose and insulin responses
Intervention Details
Evidence from Studies
Supporting Evidence (2)
This study examined time-restricted feeding in humans and found improvements in glucose control with early time-restricted feeding. While it doesn't directly study 72-hour fasts, it demonstrates that fasting patterns affect glucose metabolism. The study's findings that eTRF reduced mean 24-hour glucose by 4 mg/dl and glycemic excursions by 12 mg/dl support the concept that fasting patterns influence glucose tolerance, though the specific impairment from 72-hour fasts would need to be confirmed by other studies.
This study measured metabolic changes during prolonged fasting, including declining blood glucose and insulin levels during the fast itself. While it doesn't specifically measure glucose tolerance after the fast, the documented changes in metabolic parameters during prolonged fasting support the physiological basis for impaired glucose tolerance after extended fasting periods.