Eating large quantities of instant noodles over a long period of time may lead to weight gain because instant noodles are usually rich in high calories, salt and fat. The following are some of the factors that may lead to weight gain:

1. High calorie content: Instant noodles usually contain relatively high calorie content. If instant noodles are consumed in large quantities over a long period of time, the total calorie intake may exceed the body's needs, leading to excess energy and hence weight gain.

2. High salt content: Instant noodles usually contain seasonings and additives that are high in salt. High salt intake can lead to water retention in the body, increasing the risk of weight and edema.

3. High oil content: Instant noodles usually contain high oil content in seasonings and fried noodles. Long-term intake of high-fat foods may increase the risk of fat accumulation in the body, leading to weight gain.

In addition, instant noodles often lack balanced nutrients such as protein, fiber and vitamins. Prolonged consumption of instant noodles as a staple food may lead to malnutrition and health problems.

Consuming large quantities of instant noodles over a long period of time may therefore lead to weight gain and health risks. To maintain a healthy weight and good nutritional balance, it is recommended to eat a varied diet that includes the intake of various types of food, such as vegetables, fruits, whole grains, proteins and healthy fats, and to reasonably control the intake of instant noodles and other processed foods. In addition, a balanced diet should be combined with moderate exercise and a healthy lifestyle to maintain good health.