The Human body is incredibly resilient and it's ability to survive without food but water is a testament to it's adaptability. there's no such thing like telling accurately that what would be the actual deadline of surviving without food nut with water, Research says, that a person could survive up to 3 weeks without consumption of food as long as they can have water:

Factors Affecting Survival:  

• Body Weight and Composition:- Persons, with higher body fat may survive loner without food, because when they skip eating for long, their body starts consuming energy from their fat, in present time, this is a method of loosing weight, called Keto-diet. where you eat meal in very low amount and replacing them with fat to help your body burn fat for energy.
• Hydration Level:- A lot of water intake is crucial to survive if you skipping meal for too long, even if mild dehydration occurs, it can ruin your fasting.
• Environmental Condition:- Humid weather, temperature and exposure to elements can easily affect the survival period.
• Overall Health:- If your health is perfectly fine, not having any minor disease, then you can survive long without having food.

What Happens to your body during fasting?
When you stop eating for long, your body undergoes a lot changes to store energy from different sources:

• Ketosis:- After 2 to 3 days the body starts consuming energy through your fat, processes ketones in this process.
• Protein Breakdown:- As you continue your fasting for 4-5 days straight, your body begins to break down muscle tissues to get the energy or fuel for your body.
• Glucose Depletion:- The body uses stored glucose for energy, which will last for 24 hours.

Conclusion:
While human body can survive for up-to 3 weeks without food but with water, it's essential to take precaution and under medical supervision, especially if you have any health conditions, extended fasting can cause health risk too.