A large study published in the Journal of the American Dietetic Association followed 2,000 American girls over a 10-year period. It found that girls who demonstrated a consistent cereal-eating pattern had healthier body weights and lower Body Mass Index (BMI) than those who did not. Frequency of breakfast consumption and cereal consumption declined with age, but girls who continued to eat cereal frequently maintained a healthier body weight through adolescence.
Ready-to-eat cereals, including sweetened cereals, also made significant nutrient contributions in the diets of the girls. Forty-one percent of the cereals consumed in the study were sweetened. Still, the number of days eating cereal — including sweetened cereal — remained predictive of lower BMI and higher nutrient intakes.1
A second study on the connection between eating breakfast and maintaining a healthy weight reported similar results. Cereal consumption was associated with better nutritional status and a lower likelihood of weight gain among adolescents. This study found that although the frequency of breakfast eating declined with age, days on which the girls ate breakfast were associated with higher calcium and higher fiber intake.2 Another study found that breakfast consumption is associated with a lower body weight,3 especially when cereals are consumed, while yet another study found that people who reported consuming a breakfast of cereal had healthier body weights than those who consumed higher fat breakfasts.4

1 Barton BA, et al. The relationship of breakfast and cereal consumption to nutrient intake and body mass index: The National Heart, Lung and Blood Institute Growth and Health Study. J Am Diet Assoc. 2005;105:1383-1389.
2 Affenito SJ, et al. Breakfast consumption in African-American and white adolescent girls correlates positively with calcium and fiber intake and negatively with body mass index. J Am Diet Assoc. 2005;105:938-945.
3 Song WO, et al. Is consumption of breakfast associated with Body Mass Index in U.S. adults? J Am Diet Assoc. 2005;105:1373-1382.
4 Cho S, et al. The effect of breakfast type on total daily energy intake and body mass index: Results from the Third National Health and Nutrition Examination Survey (NHANES). J Am Coll Nutr. 2003;22(4):296-302.