Regional cerebral blood flow during exposure to food in obese binge eating women.

Cerebral responses elicited by the sight of food were evaluated in eight obese binge eating, 11 obese and 12 normal-weight non-binge eating women. Regional cerebral blood flow (rCBF) was mapped while the subjects were looking at a picture of a landscape (control) or at a portion of food (food exposure), and was measured by [99mTc]ethyl-cysteine-dimer and single photon emission computed tomography. Exposure to food was associated with different changes in the cerebral blood flow (normalized to mean cerebellar counts) of the right and left hemispheres in the obese binge eating than in the obese or normal-weight non-binge eating women. As compared with the non-binge eating groups, the obese binge eating women had, due to food exposure, a greater increase in the cerebral blood flow in the left than right hemisphere, especially in the frontal and pre-frontal regions. In addition, strong linear correlations were observed in this group between the rCBF of the left frontal and pre-frontal regions and the increase in the feeling of hunger during the exposure to food. Left hemisphere and its frontal and pre-frontal regions could thus play a role in binge eating behavior in humans.

Serum leptin and regional cerebral blood flow during exposure to food in obese and normal-weight women.

Leptin is an adipocyte-derived product of the ob gene thought to be involved in the regulation of eating. Receptors for leptin have been found in multiple regions in the brain. In particular, hypothalamic receptors seem to be of fundamental importance for the biological effects of leptin. However, the association of leptin with cerebral function in humans has not been studied. Therefore, in order to assess the possible functional relationships between leptin and cerebral activity in humans, simultaneous serum leptin and regional cerebral blood flow (rCBF) measurements were made in 10 obese [BMI 33.5 (29.3-39.1) kg/m2] and 12 normal-weight [BMI 22.2 (20.3-24.6) kg/m2] women during exposure to food. The rCBF measurements were performed by 99mTc-ethyl-cysteine-dimer single photon emission computed tomography. A strong inverse association was observed between the leptin and rCBF of hypothalamus during the exposure to food in the obese (r = -0.73, p = 0.02, n = 10), but not in the normal-weight subjects (r = 0.22, p = 0.48, n = 12). This suggests that the association of leptin with cerebral activity could be different in obese and normal-weight women; depressed activity of hypothalamic neurones in response to the high peripheral leptin concentration could be postulated to occur in obese women during exposure to food.

Serum leptin, food intake and preferences for sugar and fat in obese women.

OBJECTIVE: To examine the association of leptin with food intake and preferences for sugar and fat in obese humans. METHOD: Food intake and preferences for sugar and fat were measured in 35 obese women by a four-day food record and three hedonic tests, respectively. RESULTS: High fasting serum leptin concentration adjusted for body fat mass and dietary underreporting was associated with low dietary energy and fat intakes. In addition, trends towards lower preference for chocolate as well as for the taste of high-fat, low-sugar mixture were observed in those with higher leptin concentration. CONCLUSION: High serum leptin concentration could be associated in obese women with lower dietary energy and fat intakes, and possibly with the lower preference for fat. These findings need to be verified in further human studies.

Regional cerebral blood flow during food exposure in obese and normal-weight women.

The cerebral responses elicited by the sight of food and food-related cues are poorly known in humans. Therefore, regional cerebral blood flow (rCBF) was measured during food exposure in 11 obese and 12 normal-weight women. The rCBF was mapped while the subject was looking at a picture of a landscape (control) or at a portion of food (food exposure), and was measured by 99mTc-ethyl-cysteine-dimer single photon emission computed tomography. In the obese women, the rCBF was higher in the right parietal and temporal cortices during the food exposure than in the control condition. In addition, in the obese women the activation of the right parietal cortex was associated with an enhanced feeling of hunger when looking at food. No such changes or associations were seen in the normal-weight women. In conclusion, exposure to food is associated with increases in the rCBF of right parietal and temporal cortices in obese women, but not in normal-weight women.

Subjective and physiological cephalic phase responses to food in obese binge-eating women.

OBJECTIVE: The subjective and physiological cephalic phase reactivity to food was investigated in obese binge-eating women. METHOD: Eleven obese binge-eating women and 10 obese nonbinge-eating women participated in a cephalic phase response test consisting of baseline, anticipation, food exposure, and free eating periods. Serum insulin, free fatty acids, and plasma glucose concentrations as well as salivation, feeling of hunger, and desire to eat were repeatedly measured during the test. RESULTS: During the food exposure, the binge eaters reported more desire to eat than did the nonbinge eaters. No differences were found between the groups in the physiological cephalic phase responses except for the lower salivation in the binge eaters during the food exposure. The amount of food eaten after the food exposure was similar in both groups. DISCUSSION: Binge-eating women are characterized by stronger subjective but not stronger physiological cephalic phase reactivity to food.

Determinants of the cephalic-phase insulin response in obese nondiabetic subjects.

Large interindividual variation is characteristic of the cephalic-phase insulin response (CPIR). Our aim was to examine the largely unknown determinants of CPIR in obese nondiabetic subjects before and after weight reduction. After a 12-hour overnight fast, 20 healthy, obese (body mass index, 31.1 to 41.4 kg/m2) subjects were individually exposed to food without being allowed to eat it. Levels of insulin, glucose, C-peptide, free fatty acids, and salivation, together with assessments of feeling of hunger and desire to eat, were measured during the experiment. Subjects were divided into three groups according to CPIR before the weight reduction: positive (PR), intermediate (IR), and negative (NR) responders. CPIR measurements before and after weight reduction correlated significantly with each other (r = .61, P < . 01,n=18). At the beginning of the study, NR had higher fasting plasma glucose and insulin values, as well as higher postload plasma glucose values, as compared with PR and IR. These differences disappeared after weight reduction. In an intravenous glucose tolerance test (IVGTT) performed 9 to 12 months afterward, first-phase insulin secretion was significantly lower in NR. Thus, the negative CPIR during visual and olfactory exposure to food-related stimuli may be related to the attenuated first-phase insulin secretion and mildly impaired glucose metabolism, possibly related to insulin resistance.