Effects of fat content, weight, and acceptability of the meal on postlunch changes in mood, performance, and cardiovascular function.

This study examined the effects of fat content and meal size on postlunch changes in mood, performance, and cardiovascular function. Forty-six subjects (20 males, 26 females) were tested before and after lunch. Subjects were assigned to one of the following lunch conditions: a) low fat (23 g), large meal (860 g); b) low fat (18 g), small meal (600 g); c) high fat (84 g), large meal (840 g); d) high fat (79 g), small meal (530 g). The results showed only small effects of fat composition and meal size, with no cardiovascular effects being observed and no evidence of fat content or the weight of the meal influencing performance of logical reasoning or cognitive vigilance tasks. A few effects of meal type were significant in the mood data, but given the large number of analyses conducted, these could represent chance effects. Results from two selective attention tasks showed that subjects given the high-fat meals responded more slowly but more accurately, which differs from the effects of carbohydrate, protein, and calorie content reported in earlier papers. Weight of the meal influenced the degree of distraction from near and far distractors and also the accuracy of responses to central and peripheral targets. However, both the effects of fat and meal size were modified by task parameters, and further research is required before firm conclusions can be drawn about the functional importance of the influences of nutrient content and meal size on performance. The high-fat and large meals were rated as more acceptable than the low-fat and small meals.(ABSTRACT TRUNCATED AT 250 WORDS)