YouTuber Justin Dorff recounts week‑long water fast, reports dramatic energy shift and weight loss
The Pennsylvania health coach said days three and four were the most difficult before reporting increased focus and a more than 10‑pound weight drop; experts warn prolonged fasting carries risks.
Justin Dorff, a Pennsylvania‑based health coach and YouTuber, said a seven‑day water‑only fast produced both severe short‑term symptoms and a striking recovery in energy and focus by its fifth day, and resulted in more than a 10‑pound reduction in body weight and a noticeable decrease in waist circumference.
In a recent video shared on his channel, which has roughly 24,000 subscribers and has attracted nearly 100,000 views for this episode, the 42‑year‑old described tracking mood, cravings, hunger and energy through the challenge he called the "Great Reset." He began the fast at about 148.1 pounds (67.2 kg) with a 32‑inch (81.3 cm) waist and said he ended the seven days having lost over 10 pounds and about 10.5 inches around his waist.
Dorff said the first 20 hours were "fairly normal," with little hunger or cravings. He reported a marked decline in energy and mood by the second day and said the second through fourth days were "fantastically rough," describing nausea, fogginess, cold extremities and a hollow feeling. He said he used multivitamins, electrolyte capsules and salt water to manage headaches and other symptoms.
On the fifth day, Dorff said his condition shifted dramatically: he woke with renewed energy, improved focus and better performance in workouts. By day six he reported weighing about 139.6 pounds (63.3 kg). He said that, beyond physical changes, cravings for junk food disappeared and he experienced psychological benefits he described as a reset of "body, mind and spirit." Dorff has previously documented other nutrition and longevity experiments, including extended fasts and restrictive diets, on his channel.
Intermittent fasting and longer fasts have become more visible in recent years, adopted or publicized by some public figures and promoted by proponents for benefits such as weight loss, improved metabolic markers and stimulation of cellular processes. Research has identified metabolic shifts during fasting: after glucose stores are depleted, the body increases fat metabolism and ketone production, and periods of fasting can trigger cellular recycling processes commonly referred to as autophagy.
Medical researchers and clinicians, however, remain divided on the safety and long‑term efficacy of extended fasting. Some studies have reported short‑term improvements in weight and metabolic indicators, while other research and expert commentary stress potential harms. Critics note that some individuals compensate for fasting by consuming larger meals during eating periods, which can negate calorie reduction. Others have warned that prolonged fasting can provoke digestive disturbances, exacerbate existing conditions, or produce nutrient deficiencies.
Scientific literature and public health authorities caution that elevated ketone levels can, in certain circumstances, lead to diabetic ketoacidosis — a dangerous condition predominantly seen in people with insulin deficiency — and that prolonged exposure to altered metabolic states may carry cardiovascular or other risks. Researchers have also urged caution about claims that extended fasting confers long‑term anti‑aging benefits, noting that autophagy is a complex cellular process that, if excessively activated, could theoretically contribute to cellular harm.
Experts contacted in prior reporting say medical supervision is advisable for prolonged or repeated multi‑day fasts, particularly for people with chronic conditions such as diabetes, cardiovascular disease or eating disorders, or those taking prescription medications. Nutritionists and clinicians recommend that individuals considering extended fasts consult a healthcare professional and discuss monitoring strategies, electrolyte replacement and criteria for ending a fast if adverse symptoms arise.
Dorff characterized his experience as difficult but ultimately beneficial for his personal goals, noting both physical changes and a subjective improvement in appetite control and mental clarity. His account adds to a growing body of anecdotal reports from influencers and participants who experiment with extended fasts, while researchers and clinicians continue to evaluate the balance of potential short‑term benefits against possible risks and unknown long‑term effects.
Public health guidance typically emphasizes individualized care and caution. For those considering any extended dietary restriction, clinicians advise discussing the plan with a physician or registered dietitian to assess risks, establish monitoring, and ensure that any nutrient or electrolyte needs are addressed.