The key selling point of aspartame is as a low cal 'diet aid'. However, it has been shown that the use of this product actually causes people to consume more food. Normally when a significant quantity of carbohydrate is consumed, serotonin levels rise in the brain. This is manifested as a relaxed feeling after a meal.

When aspartame is ingested with carbohydrates, such as having pasta or a sandwich with a diet drink, aspartame causes the brain to cease production of serotonin, meaning that the feeling of having enough never materializes, let alone the 'feel good factor feeling'.