Why People Overeat
There are some physiological reasons why people may overeat relating to the ways they eat, rather than simply their diet.
Nutrient deficiencies
Sometimes people are not getting sufficient nutrients from the foods they are eating. Perhaps their diet is too high in refined sugars and processed carbohydrates so that their body simply can't extract all the nutrients it needs.
Inappropriate measures
Some people measure everything out in prescribed amounts without giving much thought to how useful those quantities are for them, and their dietary needs. Sometimes the quality of the food varies so much that a 100g portion of one source has considerably better nutritional value than 100g of the same food from another source.
Eating too fast
Often people don't take the time to savour their food. Instead they rush through eating as though it is a chore to have to eat. As such, they are not savouring their food or chewing it sufficiently to satisfy their appetite.
Lack of regularity
There are many people who eat different meals at different times each day. On some days they may skip breakfast or eat supper just prior to going to bed. Doing so sends mixed signals to the brain and can cause confusion about release of hormones and digestive enzymes associated with eating. A body which is occasionally starved of meals will build up more storage fat to allow for the lean times. Getting into a routine is much wiser.