Lipid and other plasma markers are associated with anxiety, depression, and fatigue.

OBJECTIVE: Few peripheral metabolites have been shown to be associated with mood in healthy individuals or patients with central nervous system diseases. During military basic combat training (BCT), mood state, physical performance and body composition substantially improve, providing an opportunity to examine relationships between mood and nutritional and hormonal biomarkers. METHOD: Thirty-five females enrolled in U.S. Marine BCT, an intense physically and mentally challenging 12-week course, were studied. Every 4 weeks, mood was assessed with the Profile of Mood States (POMS), as were nutritional, metabolic and hormonal plasma markers. RESULTS: Mood and fitness improved over BCT, and there were substantial changes in biochemical markers. Multiple regression demonstrated that, in combination, cholesterol (HDL, LDL), fructosamine, triglycerides, free fatty acids (FFA), dehydroepiandrosterone-sulfate (DHEA-S), ACTH, and substance P accounted for 44% of variation in anxiety, 40% confusion, 37% fatigue, 27% depression and 40% in total mood (p < .0001). Increased HDL, FFA, DHEA-S, and substance P were associated with degraded mood (p < .05). Increased LDL, triglycerides, fructosamine, and ACTH were associated with improved mood (p < .05). Other markers, including glucose, cortisol, and C-reactive protein were not associated with mood. CONCLUSIONS: Normal human mood state was associated with 8 plasma markers. Increased HDL and lower LDL, which are associated with improved cardiovascular status, were associated with negative affect. Fructosamine and substance P, not previously known to be related to mood, were associated with it. We are not aware of any biological parameters that in aggregate predict such a substantial proportion of variation in normal mood.

Effect of portion size information on food intake.

The term portion size is used differently by food manufacturers, regulatory agencies, and consumers. As such, it is unclear how information about portion size may influence perceived satiety and intake of foods by consumers. The objective of this study was to examine how portion size information influences satiety and intake, and how consumers interpret the term portion size. A randomized controlled design was used in which subjects were served a lunch meal consisting of a preload of pasta followed by ad libitum servings of the same pasta. In each of three separate sessions the subjects were told that the preload meal constituted 1/2, 1, or 1 1/2 portions of pasta. Thirty-three normal-weight subjects (22 males and 11 females) were recruited from a 250-member volunteer employee panel at Natick Research, Development, and Engineering Center during January 2005. Main measures were pre- and post-preload hunger/fullness ratings, liking ratings, amount consumed of the pasta after the preload, and Likert ratings of statements about different definitions of portion size. Results showed that portion size information did not influence satiety ratings or total intake. Consumers associated portion size more with daily nutrient requirements than with an ideal quantity for a satiating meal (P<0.01). Information about portion size may not be a good tool to manipulate food-intake behavior. Consumers' concept of portion size is associated more with objective measures of food than with personal experience about the amount that would be appropriate to eat.

The effects of movement and physical exertion on soldier vigilance.

INTRODUCTION: The effects of movement and physical exertion on cognitive processes remain unclear. Some studies report improvements in information processing while others report decrements or no change. To address relationships between movement, physical exertion, and cognitive performance, vigilance performance while soldiers walked with a heavy (40 kg) load was examined. METHODS: Volunteers (n = 18) completed six 30-min test sessions on separate days: standing; walking with or without obstacles; while carrying a 40-kg load or no load. Suprathreshold visual, auditory or tactile stimuli were presented during the vigilance task. Dependent measures included accuracy, response time and distance traversed. RESULTS: Volunteers reported higher perceived exertion (p < 0.05) when carrying a load and these ratings increased with time (p < 0.05). There were fewer correct responses on the vigilance task when carrying a load (p < 0.05) or when walking over obstacles (p < 0.05). Vigilance performance was superior with auditory compared with visual or tactile stimuli (p < 0.05). Less distance was covered when carrying a load (p < 0.05), traversing the course with obstacles (p < 0.05), and when responding to a tactile, compared with an auditory, stimulus (p < 0.05). DISCUSSION: These results indicate walking around obstacles and the exertion of load carriage affect performance on the basic cognitive function of vigilance. Furthermore, they raise fundamental questions about whether cognitive performance data collected from sedentary, rested volunteers are applicable to individuals, including dismounted soldiers, engaged in tasks that concurrently require physical and cognitive resources.

Development and testing of a labeled magnitude scale of perceived satiety.

Satiety ratings are often made using VAS or simple category scales. In order to establish a simple, more quantitative technique to index perceived hunger and/or fullness, research was undertaken to develop and test a labeled magnitude scale of satiety. Thirty-seven subjects rated the semantic meaning of 47 phrases describing different levels of hunger/fullness using magnitude estimation. Eleven phrases were then selected using criteria of response consistency, symmetry, bipolarity, and inclusion of the end-point anchors of 'greatest imaginable hunger (fullness)'. These phrases were placed along a vertical line scale at positions corresponding to their geometric mean magnitude estimates to create a labeled magnitude scale of satiety. This Satiety Labeled Intensity Magnitude (SLIM) scale was compared to VAS scales for sensitivity and reliability in two studies. In one image-based study, ANOVA with post-hoc tests showed the SLIM scale to have greater sensitivity and to have an average reliability coefficient of 0.90. In a second study using three different foods replicated on two consecutive weeks, reliability was found to be highest for the SLIM scale. It is concluded that the SLIM scale is a sensitive, reliable, and easy-to-use scale for measuring perceived satiety that has several advantages over other, more commonly used satiety scales.

A comparison between liking ratings obtained under laboratory and field conditions: the role of choice.

The relationship between laboratory and field data was investigated for nine different groupings of 5-7 foods: two main dish groupings, four snack item groupings, and three specific meals. Liking ratings on the nine-point hedonic scale were obtained in an US Army field study and for the same foods in a sensory laboratory. In a subsequent choice simulation laboratory with two food groupings, we offered subjects some choice (three out of six or seven items) among to which foods they would evaluate. The results showed high correlations between lab and field ratings for the snack food groupings (0.58-0.94), but low correlations for the main dishes (-0.05-0.26) and meal components (-0.07-0.41). Correlations between mean field and mean laboratory data improved when laboratory subjects were offered a choice of foods. The ability of laboratory ratings to predict acceptability of foods consumed under realistic conditions appears to depend on the type of food, and may be better for foods used as snacks than for main dishes. Laboratory conditions in which subjects had some degree of choice among foods improved the relationship with the field data. It is important to pay more attention to experimental variables that may improve the validity of sensory laboratory tests.

Food acceptability in field studies with US army men and women: relationship with food intake and food choice after repeated exposures.

Laboratory data with single exposures showed that palatability has a positive relationship with food intake. The question addressed in this study is whether this relationship also holds over repeated exposures in non-laboratory contexts in more natural environments. The data were collected in four field studies, lasting 4-11 days with 307 US Army men and 119 Army women, and comprised 5791 main meals and 8831 snacks in total. Acceptability was rated on the nine point hedonic scale, and intake was registered in units of 1/4, 1/2, 3/4, or 1 or more times of the provided portion size. Correlation coefficients between individual acceptability ratings and intakes varied from 0.22 to 0.62 for the main meals (n=193-2267), and between 0.13 and 0.56 for the snacks (n=304-2967). The likelihood of choosing a meal for the second time was positively related to the acceptability rating of the meal when it was consumed for the first time. The results reinforce the importance of liking in food choice and food intake/choice behavior. However, the magnitude of the correlation coefficients between acceptability ratings and food intake suggest that environmental factors also have an important role in determining intake and choice.