Your weight is a fine balance between the energy you burn off (the amount of physical activity you do) and the energy you consume (the food you eat).
If your daily energy intake from food is the same as the calories your body needs each day, your weight will stay the same. In other words, your body will be in energy balance.
If your daily energy intake from food is more than the calories your body needs, your weight will increase. This is because your body will store the extra energy as fat. This is your body's way of protecting you against famine. If food did become scarce, the fat you have stored would provide your body with energy for quite some time.
In today's society, it is very rate to have a shortage of food, so if we consume more energy than we need, we put on weight.
What is the relationship between weight and health?
As the amount of excess weight increases, so does the risk of heart disease, high blood pressure, diabetes, high cholesterol, gallstones, certain respiratory disorders, some types of cancer, and premature death. Fortunately, losing weight and keeping it off may produce health benefits for many people with excess weight, especially those who are at risk of other diseases.