What Happens If You Drink Only Water for a Week?

Early 20th-century health and fitness guru Bernarr Macfadden chronicles his seven-day, water-only fast in his book "Fasting, Hydropathy and Exercise." Macfadden, a weak child and teen, advocated short periods of fasting particularly for aiding the body in overcoming illness. The seven day fast, his longest to that point, conferred some surprising physical and mental boons.

Strength Variations

• Unlike most fasters, bodybuilder Macfadden exercised strenuously during his fast, walking 10 miles each morning. The first mile or two would be difficult, then he would gain his strength and complete the distance without trouble. At the end of the seven days, he tested himself with barbells of various weights and concluded that his strength was equal to or greater than when not fasting.

Weight Loss

• Macfadden's weight loss was doubled, he estimates, by the amount of physical exertion he undertook during his fast. The first day he lost five pounds, the second day two pounds and another eight pounds over the rest of the week. His overall appearance became more haggard or less full during this time.

Sleeplessness

• Macfadden sometimes had difficulty falling asleep during the course of the fast due to his strong hunger pangs. Drinking glasses of cold water helped him soothe his stomach and fall asleep.

Mental Clarity

• While Macfadden experienced some sluggishness during the first few days of his fast, his mind was exceptionally clear and he was able to focus on his work with less effort than needed when eating regularly.