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Two experiments were carried out to examine how spreading food intake between either two or four occasions would affect mood and cognition. The first experiment used 96 participants in a between subject design where participants received either two milkshakes at 09:00 and 13:00 or four (half nutrient content but same volume) milkshakes at 09:00, 11:00, 13:00 and 15:00. The results showed that verbal reasoning accuracy improved in the four-milkshake condition. The second experiment used 24 participants in a cross-over design. The breakfast and lunch were halved in one condition and not in the other so participants either ate breakfast and lunch, or four meals at the same times as experiment 1. Verbal reasoning accuracy was improved by spreading the intake over four meals such that errors were reduced by between 30 and 40%. Speed was also increased in a five-item (but not one-item) search task. Further research is now necessary to uncover the mechanisms that underlie these effects.

Previous research has indicated that chewing gum enhances reported alertness, but has variable effects on attention. Demand characteristics may explain these effects. The current study investigated the effects of gum and demand characteristics on attention and reported mood over time. Participants completed measures of mood and attention, with and without chewing gum. To manipulate demand characteristics, they were told that the hypothesised effect of gum was either positive or negative, or no hypothesis was mentioned. Attitudes towards gum were assessed pre- and post-manipulation. Gum increased reported alertness; this effect was only significant for positive and neutral demand characteristics. Vigilance accuracy was reduced for chewing gum, but only in the fourth minute of the task, and gum reduced focussed attention accuracy, but only for the first 64 trials. Demand characteristics did not moderate time-on-task effects. Gum improved selective attention. A positive effect on response organisation was observed; this was significant when demand characteristics and pre-test attitudes to gum were both negative. The results suggest that demand characteristics moderate effects on self-reported alertness and response organisation, but cannot explain time-on-task effects or variable main effects on other aspects of attention.

Recent research has indicated that chewing gum can relieve perceptions of stress in an occupational sample (Smith, 2009). In the present study, 72 students completed 2 weeks of either chewing gum or refraining from chewing gum. They completed scales measuring perceived stress, anxiety, depression, and single item measures of work levels and tiredness. These were completed both pre- and post-treatment. Perceived stress decreased as a function of the amount of gum chewed. The chewing gum condition was also associated with a decrease in not getting enough academic work done. There were no significant effects of chewing gum on mental health outcomes. These results confirm some of findings from previous studies of chewing gum and stress in other samples.

An intervention study was carried out to examine the effects of chewing gum on occupational stress and related outcomes. 101 volunteers from Cardiff University completed the study. The results showed that chewing gum reduced stress (both at work and outside work), reduced fatigue, reduced anxiety and depression and led to a more positive mood. Chewing gum was also associated with perceptions of better performance (both at work and outside).

This study examined the effects of the size of the meal on post-lunch changes in attention, mood, blood pressure and pulse. Thirty-five females subjects were tested before and after lunch. One group (n = 12) were than given a normal-sized lunch, another (n = 11) were given a lunch designed to contain 40% more energy than their individual requirement and the third group (n = 12) had a lunch with an energy content 40% less than the estimated requirement. After lunch all groups of subjects reported that they felt more feeble, dreamy and bored, and less alert, excited, clear-headed, energetic, quick-witted, friendly, sociable and elated. However, the size of the meal did not alter the extent of the pre/post-meal differences. Similarly, there was no effect of meal size on pulse rate or blood pressure, although pre/post-meal differences were observed. In contrast, subjects who had a larger lunch than normal made more errors on focussed attention and search tasks (especially the search task) than those who had a normal-sized lunch or one which was smaller than normal.

A study of 376 young British adults showed that estimated daily caffeine consumption increased with age, and was associated with smoking and greater alcohol consumption. Non-consumers of caffeine avoided tea and coffee (even the de-caffeinated form). Level of caffeine consumption was not associated with impulsivity, sociability, extraversion or trait anxiety.

Two experiments examined the effect of breakfast (1.89 MJ) and caffeine (4 mg/kg) on cognitive performance, mood and cardiovascular functioning. In the first experiment, breakfast had no effect on performance of sustained attention tasks, but it increased pulse rate and influenced mood. The mood effects after breakfast differed between a cooked breakfast and a cereal/toast breakfast. In contrast to the effects of breakfast, this relatively high dose of caffeine improved performance of the sustained attention tasks, increased blood pressure and increased mental alertness. In the second experiment, effects of a breakfast and caffeine on mood and cardiovascular functions confirmed the results of the first study. The breakfast improved performance on free recall and recognition memory tasks, had no effect on a semantic memory task and impaired the accuracy of performing a logical reasoning task. In contrast to this, caffeine improved performance on the semantic memory, logical reasoning, free recall and recognition memory tasks. Overall, these results show that breakfast can improve performance in some but not all cognitive tasks and that these changes are very different from those observed after lunch, and those produced by caffeine.

An experiment was carried out to examine the effects of an evening meal and caffeine (3 mg/kg) on performance, mood and cardiovascular functioning. Subjects given a meal reported that they felt stronger, more proficient and more interested than subjects in the no-meal condition. They also performed a logical reasoning task more quickly than the no-meal group. However, no effects were found on sustained attention tasks or tasks involving recall or recognition of word lists. The effects of evening meals are, therefore, different from either those observed after lunch or breakfast. Caffeine improved alertness and performance on sustained attention tasks for the group as a whole. Interactions between caffeine conditions and levels of impulsivity of the subjects were also found in memory tasks.

The purpose of this study was to investigate definitions of snacking, perceptions of snack foods and snacking behavior. One hundred and thirty six participants (96 females, 40 males, mean age 37 years), who were either students or members of the general public took part in the study. The participants completed a snacking questionnaire which measured their snacking behavior and beliefs. The majority of participants believed that snacking was best defined as food or drink eaten between main meals. The majority of participants consumed at least one snack per day (80%) and had on average 4.5 eating episodes per day. Participants were able to group snack foods depending on their differing qualities with sub-groups of the sample consuming snacks from these groups. This study supports previous evidence that snacks are best defined relative to meals however it highlights a need for further research to be done examining the relationship between meals and snacks. The findings identify that not all snack foods provide extra calories and therefore snacking is not necessarily a predisposition to obesity.

Effects of meal composition on post-lunch changes in performance efficiency and mood were examined. Lunch had an effect on mood, with subjects feeling more lethargic, feeble, clumsy, muzzy, dreamy, bored and mentally slow after the meal. However, the composition of the lunch did not influence this effect. High starch and high sugar meals slowed reactions to visual stimuli presented in the periphery, whereas consumption of a high protein lunch was associated with greater susceptibility to distraction from stimuli close to the target. These results show that protein and carbohydrate meals affect different aspects of attention. That is, the behavioural effects of a meal depend both on its composition and on the particular nature of the activity being carried out.