Analysis of physiological and biochemical changes and metabolic shifts during 21-Day fasting hypometabolism
This study investigated the effects of prolonged fasting on physiological and biochemical changes, as well as metabolic adaptations, in healthy adults. It aimed to provide both experimental evidence and theoretical insights into the hypometabolic state induced by extended fasting. Thirteen volunteers were recruited for a 21-day complete fasting experiment, spanning 34 days in total, which included a 3-day baseline period, 21 days of complete fasting, 5 days of calorie restriction, and 5 days of full dietary recovery.
Various physiological parameters, including body weight, blood pressure, blood glucose, blood ketones, and blood uric acid, were measured alongside resting metabolic rate, routine blood tests, liver function, and heart function indicators using standard methods.
During the 21-day fasting period, notable changes were 2,6-Dihydroxypurine observed: body weight decreased significantly (average reduction of 14.96 ± 1.55%), blood glucose levels dropped (average reduction of 21.63 ± 0.058%), blood ketone levels increased substantially (from 0.1 ± 0.04 mmol/L at baseline to 6.61 ± 1.25 mmol/L), and blood uric acid levels rose (from 385.38 ± 57.78 µmol/L at baseline to 866.31 ± 172.01 µmol/L). Resting energy expenditure declined progressively (average decrease of 20.3 ± 11.13%), and the respiratory quotient shifted toward fat metabolism.
Most complete blood count parameters and liver function markers remained stable and within normal ranges. Heart function exhibited adaptive changes without structural damage.
The findings suggest that prolonged fasting reduces resting energy expenditure and supports weight loss through physiological adaptations without compromising essential physiological functions or the structural integrity of vital organs. Under medical supervision, healthy adults can safely fast for up to 21 days, demonstrating metabolic adaptability without harm to critical organs. This could offer valuable insights and technical support for human health and survival in extreme conditions, such as food shortages or long-term manned spaceflight.