Why did I gain 4 pounds overnight?

Suddenly gaining more than 4 to 5 pounds of weight overnight may be a sign of a serious condition that should be addressed by a medical professional. Generally, overnight weight gain is usually caused from fluid retention. Consuming foods that are high in sodium (such as salt) can cause the body to hold on to water.

Why did I gain 6 pounds overnight?

The average adult’s weight fluctuates up to 5 or 6 pounds per day. It all comes down to what and when you eat, drink, exercise, and even sleep.