Acute effects on mood and cognitive performance of breakfasts differing in fat and carbohydrate content.

Sixteen subjects consumed low-fat/high-carbohydrate (LFHC), medium-fat/ medium-carbohydrate (MFMC), high-fat/low-carbohydrate (HFLC) iso-energetic breakfasts and no breakfast in a counterbalanced order on four separate days. The LFHC breakfast was similar in macronutrient composition, though not in meal size (more kcal) and types of foods offered, to the habitual breakfast of the subjects. A battery of cognitive performance tasks together with mood and appetite ratings were completed before and during the 3 h following breakfast. Results showed no clear differences in performance between the four dietary conditions, but significant effects on mood were observed. Mood improved (a decline in fatigue/dysphoria) following the LFHC breakfast compared to the other meals. The findings show that the macronutrient content of breakfast, independent of energy value and oro-sensory qualities, can exert small but reliable effects on subsequent mood, and suggest that deviation from habitual meal composition can produce a relative decline in mood state. These conclusions are supported by results from a previous study of the effects of lunch which found very similar relationships between meal composition, habitual choices and postprandial mood changes.