In a healthy 70 kg man, glycogen stores can sustain normal activities for approximately how long?

• A. 1 day
• B. 3 days
• C. 7 days
• D. 14 days

Answer: (A)

Glycogen acts as a quick, readily mobilizable energy reserve stored mainly in the liver and skeletal muscle. In a healthy adult around 70 kg, total glycogen is limited—roughly 100 g in the liver and about 300–400 g in muscle—providing a finite amount of energy (about 400–2000 kcal, depending on how the individual uses it). For normal daily activities, this supply is typically consumed within about a day, because energy needs during routine function draw on glycogen at a rate that depletes these stores in roughly 24 hours. Once depleted, the body shifts toward fat oxidation and gluconeogenesis, which are slower processes and maintain energy less efficiently for ongoing activity.

So the most accurate takeaway is that glycogen stores can sustain normal activities for roughly one day.