What does the phrase 'a school of thought' mean?

A balanced diet means getting the right types and amounts of foods and drinks to supply nutrition and energy for maintaining body cells, tissues, and organs, and for supporting normal growth and development. Eating a balanced diet means choosing a wide variety of foods and drinks from all the food groups. It also means eating certain things in moderation, namely saturated fat, trans fat, cholesterol, refined sugar, salt and alcohol. The goal is to take in nutrients you need for health at the recommended levels. Your balanced diet must be planned at your own calorie level, and portion size is key. You want to get the most nutrients for the calories by choosing food with a high-nutrient density. Nutrient-dense foods provide substantial amounts of vitamins and minerals and relatively few calories, such as fresh fruit and vegetables, lean meat and fish, and whole grains and beans. Low-nutrient dense foods have few vitamins but lots of calories, such as candy bars, soda, donuts and onion rings. Nutrition guidelines recommend eating a wide variety of foods. But, there's a school of thought that eating variety of foods leads to overeating. There is the tendency to stay hungry longer and eat more food when flavors are diverse and keep changing because we fill up on fewer calories when flavor variety is controlled. We have seen this principle in action when we come home with a load of groceries and want to sample the wide variety of tasty foods.