**Loss of excess water and salts from the human body is called dehydration.**

Dehydration is a condition that occurs when the body loses more water than it takes in. This can happen due to various reasons such as excessive sweating, vomiting, diarrhea, or not drinking enough fluids. When the body loses water, it also loses salts and electrolytes that are essential for proper bodily functions.

**Causes of Dehydration:**
1. Inadequate Fluid Intake: Not drinking enough fluids, especially during hot weather or physical activity, can lead to dehydration.
2. Illness: Certain illnesses such as fever, vomiting, or diarrhea can cause excessive fluid loss and dehydration.
3. Excessive Sweating: Engaging in intense physical activity or being exposed to hot climates can cause excessive sweating, leading to dehydration.
4. Medications: Some medications like diuretics can increase urine production and contribute to dehydration.

**Effects of Dehydration:**
Dehydration can have various negative effects on the body, including:
1. Thirst: One of the initial signs of dehydration is a feeling of extreme thirst.
2. Dry Mouth and Lips: Dehydration can cause dryness of the mouth and lips.
3. Fatigue and Weakness: When the body is dehydrated, it may lead to feelings of fatigue and weakness.
4. Dizziness and lightheadedness: Dehydration can cause a drop in blood pressure, leading to dizziness and lightheadedness.
5. Dark Urine: Dehydration can result in concentrated urine that is dark in color.
6. Muscle Cramps: Loss of electrolytes through dehydration can cause muscle cramps and spasms.

**Preventing and Treating Dehydration:**
To prevent and treat dehydration, it is important to:
1. Drink Plenty of Fluids: It is recommended to drink at least 8 glasses of water a day and increase fluid intake during hot weather or physical activity.
2. Eat Hydrating Foods: Foods with high water content like fruits and vegetables can help maintain hydration levels.
3. Replace Electrolytes: When dehydrated, it is important to replace lost electrolytes by consuming sports drinks or electrolyte-rich foods.
4. Seek Medical Help: If dehydration is severe or accompanied by other symptoms like confusion, rapid heartbeat, or fainting, it is important to seek medical attention.

In conclusion, dehydration occurs when the body loses more water and salts than it takes in. It can have various negative effects on the body, but can be prevented and treated by drinking enough fluids, eating hydrating foods, and replacing lost electrolytes.