YouTuber reports dramatic weight loss and energy swing during seven-day water fast; experts urge caution
Justin Dorff says four difficult days gave way to renewed energy and more than 10 pounds lost; researchers warn prolonged fasts carry metabolic and cardiovascular risks
Pennsylvania-based health coach and social media creator Justin Dorff said a seven-day water-only fast produced rapid weight loss, intense days of fatigue and a sudden rebound in energy that he described as moving from “zombie to God mode.” In a YouTube video posted in May that has been viewed nearly 100,000 times, the 42-year-old said he lost more than 10 pounds and more than 10 inches around his waist during the challenge while tracking his mood, cravings and energy.
Dorff, who has about 24,000 subscribers and has previously documented extreme diet experiments, said he began the fast feeling tired and with nagging injuries. He said the first 20 hours were "fairly normal," but that the second day brought tiredness, nausea and fogginess. He reported taking multivitamins, electrolyte capsules and drinking salt water to manage headaches and cold extremities in the middle days.
Dorff described days three and four as "fantastically rough," saying he felt hollow and low in motivation. On day five, he said, the symptoms reversed: he reported improved focus, higher energy, and the ability to complete strenuous workouts without "white knuckling" through hunger. Dorff said he weighed about 148.1 pounds (67.2 kg) and had a 32-inch (81.3 cm) waist at the start; by day six he reported a weight of 139.6 pounds (63.3 kg) and said his cravings for junk food had largely disappeared by the end of the week.
Intermittent fasting and longer fasts have surged in popularity since the early 2010s, embraced by some public figures and promoted for weight loss and metabolic benefits. Researchers say fasting can lead to early depletion of glycogen stores and a switch to burning stored fat, with production of ketones that cells can use for energy. Short-term fasting also can stimulate autophagy, a cellular process that clears damaged components.
However, experts remain divided about the long-term safety and effectiveness of extended fasts. Some clinicians and researchers caution that many people compensate for fasting periods by overeating during feeding windows, negating calorie restriction. Other studies and commentaries have raised concerns that prolonged or extreme fasting could increase risk of adverse cardiovascular events, digestive problems and metabolic disturbances in susceptible individuals.
High concentrations of ketones can lead to ketoacidosis, a dangerous rise in blood acidity more commonly seen in people with insulin-dependent diabetes but sometimes cited as a theoretical risk in extreme fasting contexts. Research cited by clinicians also suggests that prolonged exposure to elevated ketone levels could have detrimental effects on cardiac tissue in certain settings. Likewise, while autophagy can be beneficial in removing damaged cellular components, scientists warn excessive or prolonged autophagy can cause cell loss and organ stress.
Medical societies generally advise that extended fasts—especially beyond 24 hours—be undertaken only under medical supervision. Clinicians stress that electrolyte imbalance, dehydration, exacerbation of underlying medical conditions and adverse psychological effects are possible during prolonged food abstinence. Nutrient supplementation such as vitamins and electrolytes, which Dorff reported using, may mitigate some symptoms but do not eliminate broader metabolic risks.
Dorff said his goal for the weeklong experiment, which he called the "Great Reset," was to reset body, mind and spirit after a period of low energy and cravings. His account aligns with anecdotal reports from some fasters who describe an initial period of discomfort followed by a perceived increase in clarity and energy. Researchers say such experiences can occur but emphasize the need for controlled trials and long-term data to determine whether benefits outweigh risks for most people.
As interest in fasting protocols continues, health professionals recommend individual assessment of medical history, supervision for prolonged fasts and attention to signs of dehydration, fainting, arrhythmia or other red flags. Public-facing accounts of extreme diets can highlight physiological responses, but clinicians say anecdotal reports should not replace medical advice or structured research on safety and efficacy.