Just add water: Effects of added gastric distention by water on gastric emptying and satiety related brain activity.

BACKGROUND: Gastric distention contributes to meal termination. There is little research on the neural correlates of gastric distention by food. To date, neural measures have not been obtained concurrently with measurements of gastric distention. OBJECTIVES: 1) To study how offering a small versus a large water load following a standardized nutrient load affects gastric distention over time. 2) To assess associations between satiety experiences and brain activity and the degree of gastric distention. METHOD: 19 healthy males (age 22.2 ±â€¯2.5 y, BMI 21.8 ±â€¯1.5 kg/m2) participated in a randomized crossover study with two treatments: ingestion of a 500-kcal 150-mL liquid meal shake followed by a low (LV, 50 mL) or a high volume (HV, 350 mL) water load. At baseline and three times after ingestion satiety was scored, MRI scans were made to determine total gastric content volume (TGV) and functional MRI scans were made to measure cerebral blood flow (CBF). RESULTS: TGV was significantly higher for HV compared to LV at all time points (p < 0.001) with relative differences between HV and LV of 292 ±â€¯37 mL after ingestion, 182 ±â€¯83 mL at t = 15 min and 62 ±â€¯57 mL at t = 35 min. Hunger decreased (p = 0.023) and fullness increased (p = 0.030) significantly more for HV compared to LV. Ingestion increased CBF in the inferior frontal gyrus and the anterior insula, but there were no differences between treatments. There were no significant correlations between appetite ratings and CBF values. CONCLUSION: Performing concurrent gastric MRI and CBF measurements can be used to investigate neural correlates of gastric distention. Increased distention did not induce significantly greater brain activation. Future research should further examine the role of the inferior frontal gyrus in satiety.

Developmental differences in the brain response to unhealthy food cues: an fMRI study of children and adults.

BACKGROUND: Food cues are omnipresent and may trigger overconsumption. In the past 2 decades, the prevalence of childhood obesity has increased dramatically. Because children's brains are still developing, especially in areas important for inhibition, children may be more susceptible than adults to tempting food cues. OBJECTIVE: We examined potential developmental differences in children's and adults' responses to food cues to determine how these responses relate to weight status. DESIGN: We included 27 children aged 10-12 y and 32 adults aged 32-52 y. Functional magnetic resonance imaging data were acquired during a food-viewing task in which unhealthy and healthy food pictures were presented. RESULTS: Children had a stronger activation in the left precentral gyrus than did adults in response to unhealthy compared with healthy foods. In children, unhealthy foods elicited stronger activation in the right inferior temporal and middle occipital gyri, left precentral gyrus, bilateral opercular part of the inferior frontal gyrus, left hippocampus, and left middle frontal gyrus. Adults had stronger activation in the bilateral middle occipital gyrus and the right calcarine sulcus for unhealthy compared with healthy foods. Children with a higher body mass index (BMI) had lower activation in the bilateral dorsolateral prefrontal cortex while viewing unhealthy compared with healthy foods. In adults there was no correlation between BMI and neural response to unhealthy compared with healthy foods. CONCLUSIONS: Unhealthy foods might elicit more attention both in children and in adults. Children had stronger activation while viewing unhealthy compared with healthy foods in areas involved in reward, motivation, and memory. Furthermore, children activated a motivation and reward area located in the motor cortex more strongly than did adults in response to unhealthy foods. Finally, children with a higher BMI had less activation in inhibitory areas in response to unhealthy foods, which may mean they are more susceptible to tempting food cues. This trial was registered at www.trialregister.nl as NTR4255.

Empty calories and phantom fullness: a randomized trial studying the relative effects of energy density and viscosity on gastric emptying determined by MRI and satiety.

BACKGROUND: Stomach fullness is a determinant of satiety. Although both the viscosity and energy content have been shown to delay gastric emptying, their relative importance is not well understood. OBJECTIVE: We compared the relative effects of and interactions between the viscosity and energy density on gastric emptying and perceived satiety. DESIGN: A total of 15 healthy men [mean ± SD age: 22.6 ± 2.4 y; body mass index (in kg/m(2)): 22.6 ± 1.8] participated in an experiment with a randomized 2 × 2 crossover design. Participants received dairy-based shakes (500 mL; 50% carbohydrate, 20% protein, and 30% fat) that differed in viscosity (thin and thick) and energy density [100 kcal (corresponding to 0.2 kcal/mL) compared with 500 kcal (corresponding to 1 kcal/mL)]. After ingestion, participants entered an MRI scanner where abdominal scans and oral appetite ratings on a 100-point scale were obtained every 10 min until 90 min after ingestion. From the scans, gastric content volumes were determined. RESULTS: Overall, the gastric emptying half-time (GE t50) was 54.7 ± 3.8 min. The thin 100-kcal shake had the lowest GE t50 of 26.5 ± 3.0 min, followed by the thick 100-kcal shake with a GE t50 of 41 ± 3.9 min and the thin 500-kcal shake with a GE t50 of 69.5 ± 5.9 min, and the thick 500-kcal shake had the highest GE t50 of 81.9 ± 8.3 min. With respect to appetite, the thick 100-kcal shake led to higher fullness (58 points at 40 min) than the thin 500-kcal shake (48 points at 40 min). CONCLUSIONS: Our results show that increasing the viscosity is less effective than increasing the energy density in slowing gastric emptying. However, the viscosity is more important to increase the perceived fullness. These results underscore the lack of the satiating efficiency of empty calories in quickly ingested drinks such as sodas. The increase in perceived fullness that is due solely to the increased viscosity, which is a phenomenon that we refer to as phantom fullness, may be useful in lowering energy intake. This trial was registered at www.trialregister.nl as NTR4573.

Human protein status modulates brain reward responses to food cues.

BACKGROUND: Protein is indispensable in the human diet, and its intake appears tightly regulated. The role of sensory attributes of foods in protein intake regulation is far from clear. OBJECTIVE: We investigated the effect of human protein status on neural responses to different food cues with the use of functional magnetic resonance imaging (fMRI). The food cues varied by taste category (sweet compared with savory) and protein content (low compared with high). In addition, food preferences and intakes were measured. DESIGN: We used a randomized crossover design whereby 23 healthy women [mean ± SD age: 22 ± 2 y; mean ± SD body mass index (in kg/m(2)): 22.5 ± 1.8] followed two 16-d fully controlled dietary interventions involving consumption of either a low-protein diet (0.6 g protein · kg body weight(-1) · d(-1), ~7% of energy derived from protein, approximately half the normal protein intake) or a high-protein diet (2.2 g protein · kg body weight(-1) · d(-1), ~25% of energy, approximately twice the normal intake). On the last day of the interventions, blood oxygen level-dependent (BOLD) responses to odor and visual food cues were measured by using fMRI. The 2 interventions were followed by a 1-d ad libitum phase, during which a large array of food items was available and preference and intake were measured. RESULTS: When exposed to food cues (relative to the control condition), the BOLD response was higher in reward-related areas (orbitofrontal cortex, striatum) in a low-protein state than in a high-protein state. Specifically, BOLD was higher in the inferior orbitofrontal cortex in response to savory food cues. In contrast, the protein content of the food cues did not modulate the BOLD response. A low protein state also increased preferences for savory food cues and increased protein intake in the ad libitum phase as compared with a high-protein state. CONCLUSIONS: Protein status modulates brain responses in reward regions to savory food cues. These novel findings suggest that dietary protein status affects taste category preferences, which could play an important role in the regulation of protein intake in humans. This trial was registered at www.trialregister.nl/trialreg/admin/rctview.asp?TC=3288 as NTR3288.