You can generally survive without food for about 2 to 3 weeks if you have access to water. Without any food or water, survival time is much shorter, typically only about 3 to 5 days. The exact duration varies widely depending on factors such as age, health, body fat, hydration, and individual metabolism

. Here is a summary of key points:

• With water but no food: Most adults can survive between 8 and 21 days, with some cases reporting survival up to 30 or even 60 days under exceptional circumstances. The body initially uses glucose and glycogen stores, then fat stores (ketosis), and finally muscle protein for energy

• Without food and water: Survival is usually limited to about one week or less due to dehydration and organ failure

• Body adaptations: After about 24 hours without food, the body shifts from glucose to fat for energy, slowing metabolism to conserve energy. Muscle breakdown occurs later, which can lead to serious health complications and death if starvation continues

• Extreme cases: The Guinness World Record for the longest medically supervised fast is 382 days, but such cases are rare and dangerous

In summary, while survival without food can extend up to several weeks with adequate hydration, going without both food and water drastically reduces survival time to a few days.