Evaluation of the Influence of Raw Almonds on Appetite Control: Satiation, Satiety, Hedonics and Consumer Perceptions

Snack foods can be substantial contributors to daily energy intake, with different types of snacks exerting potentially different effects on satiety per calorie consumed. The present research compared the effect of consuming almonds as a mid-morning snack compared to an energy and weight-matched comparator snack (savoury crackers) or the equivalent weight of water (zero energy control). In a crossover design, 42 female participants (age: 26.0 ± 7.9, BMI: 22.0 ± 2.0) consumed a fixed breakfast then a mid-morning snack. Appetite, 24-h energy intake, food hedonics, and consumer perceptions of the snack foods were assessed under laboratory conditions. AUC analyses revealed a lower overall hunger drive after consuming almonds compared to crackers or water. There was no difference in 24-h energy intake in the almond compared to the cracker or the zero-energy control condition, however participants consumed more energy in the cracker condition compared to the zero-energy control condition. In addition, almonds suppressed hedonic preference (implicit wanting) for consuming high-fat foods and demonstrated a higher satiety quotient (SQ) than crackers. Almonds were perceived to have a more favourable consumer profile aligned with successful weight management. In conclusion, these findings demonstrate that in the context of a 24-h period of objectively measured energy intake, raw almonds are effective for controlling appetite compared to an energy matched alternative snack. This trial was registered at clinicaltrials.gov [NCT02480582].

Sustained NPY signaling enables AgRP neurons to drive feeding

Artificial stimulation of Agouti-Related Peptide (AgRP) neurons promotes intense food consumption, yet paradoxically during natural behavior these cells are inhibited before feeding begins. Previously, to reconcile these observations, we showed that brief stimulation of AgRP neurons can generate hunger that persists for tens of minutes, but the mechanisms underlying this sustained hunger drive remain unknown (Chen et al., 2016). Here we show that Neuropeptide Y (NPY) is uniquely required for the long-lasting effects of AgRP neurons on feeding behavior. We blocked the ability of AgRP neurons to signal through AgRP, NPY, or GABA, and then stimulated these cells using a paradigm that mimics their natural regulation. Deletion of NPY, but not AgRP or GABA, abolished optically-stimulated feeding, and this was rescued by NPY re-expression selectively in AgRP neurons. These findings reveal a unique role for NPY in sustaining hunger in the interval between food discovery and consumption.

Hunger neurons drive feeding through a sustained, positive reinforcement signal

The neural mechanisms underlying hunger are poorly understood. AgRP neurons are activated by energy deficit and promote voracious food consumption, suggesting these cells may supply the fundamental hunger drive that motivates feeding. However recent in vivo recording experiments revealed that AgRP neurons are inhibited within seconds by the sensory detection of food, raising the question of how these cells can promote feeding at all. Here we resolve this paradox by showing that brief optogenetic stimulation of AgRP neurons before food availability promotes intense appetitive and consummatory behaviors that persist for tens of minutes in the absence of continued AgRP neuron activation. We show that these sustained behavioral responses are mediated by a long-lasting potentiation of the rewarding properties of food and that AgRP neuron activity is positively reinforcing. These findings reveal that hunger neurons drive feeding by transmitting a positive valence signal that triggers a stable transition between behavioral states.

The animal: options for managing intake

Managing voluntary feed intake of grazing animals is essential to maximise returns and to meet market specifications. Restricting nutrient intake is successfully achieved by controlled grazing management techniques and with feed additive use in intensive feeding systems. Increasing feed intake in the long-term will be a greater challenge to research. There is considerable potential with existing genotypes of sheep to increase intake, because intake appears to be limited by a lack of hunger drive rather than by limitations due to tissue energy transactions or gut load. Increasing voluntary feed intake will be successful if we can increase the hunger drive within the brain. Increasing the hunger drive may be achieved by decreasing the metabolic satiety signal arising from tissue transactions, by reducing the magnitude of the satiety signals arising from the gastrointestinal tract or by modifying neurotransmitters within the brain to enhance the hunger drive.

Psychobiology of anorexia nervosa

SynopsisThe psychobiology of anorexia nervosa is described and explained under four headings; (1) the psychopathology as related to the motivation for fasting; (2) metabolic and somatic consequences of starvation, including brain morphology; (3) endocrine abnormalities in the hypothalamic-pituitary-adrenal and gonadal axis; and (4) the hunger drive and its possible perversions in terms of aspects of neuroethology and the reward system in the brain.

Increased thirst and hunger in adult rats undernourished as infants: an alternative explanation

1. Rats were undernourished in early life by feeding their mothers a restricted quantity of a good-quality diet throughout lactation. Their undernutrition continued postweaning from 25 to 42 d of age, after which they were fed ad lib. Control rats were well nourished at all times.2. Behavioural assessment of thirst was carried out on adult males. These were deprived of water for 23 h/d throughout the period of testing. Compared to control rats, previously-undernourished (PU) rats pressed a lever at a higher rate in a Skinner box to gain a water reward, drank more frequently during their first 5 min in an unfamiliar cage, and tended to run more quickly down an alleyway for water. PU rats also drank more (/kg body-weighta0.75) of a quinine solution (1 g/l) when this was available to them ad lib. as their only source of fluid.3. A second group of rats was growth-retarded during gestation and the suckling and early postweaning periods. The rats had free access to food from 42 d of age. In adulthood their ad lib. food and water consumption was measured. PU males ate and drank more (/kg body-weight0.75) than control males.4. These results indicate that adult rats which have been undernourished in early life display increased thirst. An attempt is made to explain this finding, together with their previously-demonstrated enhanced hunger drive, purely in terms of gross anatomical and physiological differences.

Arousal and Preferences for Complexity in Infants

To determine the effects of arousal on preference for complexity 9 infants (16 to 18 mo.) were exposed to different levels of complexity under low and high hunger drive. Low-hunger Ss showed longer fixation time than high-hunger Ss toward all stimuli and showed relatively greater preference for complexity than high-hunger Ss. The results were interpreted in terms of optimal-stimulation theory and information-processing theory.