title: Reductions in portion size and energy density of foods are additive and lead to sustained decreases in energy intake.
abstract: BACKGROUND
  When the portion size and energy density (in kcal/g) of a food are varied simultaneously in a single meal, each influences energy intake independently.
  
  
  OBJECTIVE
  We aimed to determine how the effects of portion size and energy density combine to influence energy intake and satiety over multiple meals for 2 d.
  
  
  METHODS
  In a crossover design, 24 young women were provided with meals and snacks for 2 consecutive days per week for 4 wk; all foods were consumed ad libitum. Across the 4 sessions, the subjects were served the same 2 daily menus, but all foods were varied in portion size and energy density between a standard level (100%) and a reduced level (75%).
  
  
  RESULTS
  Reducing the portion size and energy density of all foods led to significant and independent decreases in energy intake over 2 d (P < 0.0001). A 25% decrease in portion size led to a 10% decrease in energy intake (231 kcal/d), and a 25% decrease in energy density led to a 24% decrease in energy intake (575 kcal/d). The effects on energy intake were additive and were sustained from meal to meal. Despite the large variation in energy intake, there were no significant differences in the ratings of hunger and fullness across conditions over the 2 d.
  
  
  CONCLUSIONS
  Reductions in portion size and energy density independently decreased ad libitum energy intake in women when commonly consumed foods were served over 2 d. Reductions in both portion size and energy density can help to moderate energy intake without increased hunger.
authors.affiliation: Nutrition Department, The Pennsylvania State University, University Park, PA 16802-6501, USA. bjr4@psu.edu
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Rolls
authors.forename: Liane S
authors.initials: LS
authors.lastname: Roe
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Meengs
mesh_terms: D000328:Adult; D018592:Cross-Over Studies; D004041:Dietary Fats / Q000008:administration & dosage*; D002149:Energy Intake / Q000502:physiology*; D005260:Female; D006801:Humans; D009753:Nutritive Value; D009765:Obesity / Q000178:diet therapy* / Q000517:prevention & control; D012528:Satiety Response / Q000502:physiology*; D011795:Surveys and Questionnaires; D013997:Time Factors; D015430:Weight Gain / Q000502:physiology
chemical_list: D004041:Dietary Fats