Barbara J. Rolls

Sensory Specific Satiety in Man

To investigate the specificity of satiety in man, subjects (n=32) rated the pleasantness of the taste of eight foods, were then given one of the foods to eat for lunch, and re-rated the pleasantness of the taste of the eight foods 2 and 20 min after the end of the meal. The pleasantness of the food eaten decreased more than that of the foods not eaten (p<0.001). In a second experiment it was shown that this relative specificity of satiety influenced subsequent food intake. Before a first course, subjects (n=24) rated their liking for the taste of eight foods, were then given one of the foods to eat for lunch, and 2 min after finishing eating re-rated their liking for the taste of the eight foods. Again liking decreased more for the food eaten than for foods not eaten. These changes in liking for the foods eaten and not eaten were highly correlated (p<0.001) with the amounts of those foods eaten in an unexpected second course. Thus in man satiety can be partly specific to foods eaten and this specificity may be an important determinant of the foods selected for consumption.

Reduced Thirst after Water Deprivation in Healthy Elderly Men

To determine whether responses to dehydration are altered with age, we investigated the thirst, fluid and electrolyte responses, and hormonal responses to 24 hours of water deprivation in seven healthy active elderly men (67 to 75 years old) and seven healthy young men (20 to 31 years old) who were matched for weight loss during water deprivation. After water deprivation, the older men had greater increases in plasma osmolality, sodium concentration, and vasopressin levels. However, their urinary osmolality was lower and they were less thirsty and drank less after water deprivation, so that their plasma and urine were not diluted to predeprivation levels. Regression analysis indicated increased sensitivity of vasopressin osmoreceptors in the older group, although this difference was not statistically significant. We conclude that after 24 hours of water deprivation, there is a deficit in thirst and water intake in healthy elderly men, as compared with younger men, although vasopressin osmoreceptor responsiveness is maintained or even increased. Our findings also suggest that the well-known deficit in urinary concentrating ability that occurs with age reflects renal causes and not a lack of circulating vasopressin.

Drinking induced by injection of angiotensin into the brain of the rat

1. When applied directly to the brain, angiotensin II amide, as either the valine5 octapeptide, causes rats in normal fluid balance to drink water.

Variety in a meal enhances food intake in man

We find that in man satiety can be partly specific to foods eaten [12]. The possibility that this specificity of satiety leads to overeating if a wide variety of foods is readily available is tested here. The intakes of subjects offered a variety of foods in succession during a meal were compared to intakes when the same food was offered throughout. Subjects (n=36) ate a third more when offered sandwiches with four different fillings than when just one filling was offered (p<0.001). In another study subjects (n=24) ate significantly more when three flavors of yogurt (hazelnut, blackcurrant, orange) which were distinctive in taste, texture and color were offered than when offered just one of the flavors (p<0.01), even if the flavor was the favorite (p<0.01). However, when subjects (n=24) were offered three flavors of yogurt (strawberry, raspberry, cherry) which differed only in taste there was no enhancement of intake when the variety was offered. Having a variety of foods presented in succession during a meal enhances intake, and the more different the foods are the greater the enhancement is likely to be.

Nonsurgical factors that influence the outcome of bariatric surgery: a review.

Objective Severe obesity (ie, at least 100% overweight or body mass index >or=to40 kg/m2) is associated with significant morbidity and increased mortality. It is apparently becoming more common in this country. Conventional weight-loss treatments are usually ineffective for severe obesity and bariatric surgery is recommended as a treatment option. However, longitudinal data on the long-term outcome of bariatric surgery are sparse. Available data indicate that the outcome of bariatric surgery, although usually favorable in the short term, is variable and weight regain sometimes occurs at 2 years after surgery. The objective of this study is to present a review of the outcome of bariatric surgery in three areas: weight loss and improvement in health status, changes in eating behavior, and psychosocial adjustment. The study will also review how eating behavior, energy metabolism, and psychosocial functioning may affect the outcome of bariatric surgery. Suggestions for additional research in these areas are made. Method Literature review. Results On average, most patients lose 60% of excess weight after gastric bypass and 40% after vertical banded gastroplasty. In about 30% of patients, weight regain occurs at 18 months to 2 years after surgery. Binge eating behavior, which is common among the morbidly obese, may recur after surgery and is associated with weight regain. Energy metabolism may affect the outcome of bariatric surgery, but it has not been systematically studied in this population. Presurgery psychosocial functioning does not seem to affect the outcome of surgery, and psychosocial outcome is generally encouraging over the short term, but there are reports of poor adjustment after weight loss, including alcohol abuse and suicide. Conclusions Factors leading to poor outcome of bariatric surgery, such as binge eating and lowered energy metabolism, should be studied to improve patient selection and outcome. Long-term outcome data on psychosocial functioning are lacking. Longitudinal studies to examine the long-term outcome of bariatric surgery and the prognostic indicators are needed.

The influence of food portion size and energy density on energy intake: implications for weight management

The increase in the prevalence of obesity has coincided with an increase in portion sizes of foods both inside and outside the home, suggesting that larger portions may play a role in the obesity epidemic. Although it will be difficult to establish a causal relationship between increasing portion size and obesity, data indicate that portion size does influence energy intake. Several well-controlled, laboratory-based studies have shown that providing older children and adults with larger food portions can lead to significant increases in energy intake. This effect has been demonstrated for snacks and a variety of single meals and shown to persist over a 2-d period. Despite increases in intake, individuals presented with large portions generally do not report or respond to increased levels of fullness, suggesting that hunger and satiety signals are ignored or overridden. One strategy to address the effect of portion size is decreasing the energy density (kilojoules per gram; kilocalories per gram) of foods. Several studies have demonstrated that eating low-energy-dense foods (such as fruits, vegetables, and soups) maintains satiety while reducing energy intake. In a clinical trial, advising individuals to eat portions of low-energy-dense foods was a more successful weight loss strategy than fat reduction coupled with restriction of portion sizes. Eating satisfying portions of low-energy-dense foods can help to enhance satiety and control hunger while restricting energy intake for weight management.

Myths, Presumptions, and Facts about Obesity

BACKGROUND Many beliefs about obesity persist in the absence of supporting scientific evidence (presumptions); some persist despite contradicting evidence (myths). The promulgation of unsupported beliefs may yield poorly informed policy decisions, inaccurate clinical and public health recommendations, and an unproductive allocation of research resources and may divert attention away from useful, evidence-based information. METHODS Using Internet searches of popular media and scientific literature, we identified, reviewed, and classified obesity-related myths and presumptions. We also examined facts that are well supported by evidence, with an emphasis on those that have practical implications for public health, policy, or clinical recommendations. RESULTS We identified seven obesity-related myths concerning the effects of small sustained increases in energy intake or expenditure, establishment of realistic goals for weight loss, rapid weight loss, weight-loss readiness, physical-education classes, breast-feeding, and energy expended during sexual activity. We also identified six presumptions about the purported effects of regularly eating breakfast, early childhood experiences, eating fruits and vegetables, weight cycling, snacking, and the built (i.e., human-made) environment. Finally, we identified nine evidence-supported facts that are relevant for the formulation of sound public health, policy, or clinical recommendations. CONCLUSIONS False and scientifically unsupported beliefs about obesity are pervasive in both scientific literature and the popular press. (Funded by the National Institutes of Health.).

How sensory properties of foods affect human feeding behavior

The sensory properties of food which can lead to a decrease in the pleasantness of that food after it is eaten, and to enhanced food intake if that property of the food is changed by successive presentation of different foods, were investigated. After eating chocolates of one color the pleasantness of the taste of the eaten color declined more than of the non-eaten colors, although these chocolates differed only in appearance. The presentation of a variety of colors of chocolates, either simultaneously or successively, did not affect food intake compared with consumption of the subjects favorite color. Changes in the shape of food (which affects both appearance and mouth feel) were introduced by offering subjects three successive courses consisting of different shapes of pasta. Changes in shape led to a specific decrease in the pleasantness of the shape eaten and to a significant enhancement (14%) of food intake when three shapes were offered compared with intake of the subjects favorite shape. Changes in just the flavor of food (i.e., cream cheese sandwiches flavored with salt, or with the non-nutritive flavoring agents lemon and saccharin, or curry) led to a significant enhancement (15%) of food intake when all three flavors were presented successively compared with intake of the favorite. The experiments elucidate some of the properties of food which are involved in sensory specific satiety, and which determine the amount of food eaten.

Increasing the portion size of a packaged snack increases energy intake in men and women

The objective of this study was to determine how the portion size of a packaged snack affects energy intake of the snack and of the subsequent meal. On five separate days, 60 subjects (34 women and 26 men) ate an afternoon snack and dinner in individual cubicles. For each snack, subjects were served one of five packages of potato chips (28, 42, 85, 128, or 170 g), which they consumed ad libitum directly from the unlabelled, opaque package. Subjects returned to the lab three hours later for a standard dinner, which was also consumed ad libitum. Results showed that snack intake increased significantly as the package size increased for both males and females (p < 0.001). The combined energy intake from snack and dinner also increased as the package size increased. On average, when served the largest snack package compared to the smallest, subjects consumed an additional 596 kJ (143 kcal) at snack and dinner combined. Results from this study demonstrate that short-term energy intake increases with increasing package size of a snack. These data suggest that the availability of large packages of energy-dense snacks may be one of the environmental influences associated with excess energy intake.

The specificity of satiety: The influence of foods of different macronutrient content on the development of satiety

The effects of consuming equicaloric preloads with different macronutrient contents on the development of satiety were investigated. Ten normal-weight, nondieting women fasted overnight and then rated hunger, fullness, and food preferences, and the pleasantness of the taste of food samples before and after five different preloads. The greatest changes in the pleasantness of the taste of the food occurred for the eaten food relative to the uneaten food. Macronutrient content of the preloads did not significantly influence the magnitude of these changes or the pleasantness of foods with similar nutrient contents. Therefore, no evidence of nutrient-specificity was obtained. Nutrient composition had a differential effect on hunger, fullness and food intake. Ratings of hunger decreased and fullness increased following the high starch and high protein preloads to a greater extent than after the high fat, high sucrose and mixed content preloads. When a self-selection meal was offered 2 hours after the preloads energy intake and preference for high carbohydrate and high fat food items were significantly decreased by the high protein and high starch preloads. However, no specific reduction in macronutrient intake was observed. In conclusion, differential effects of the preloads were observed in subjective ratings of hunger, fullness, preferences and subsequent food intake, but there was no indication that satiety was macronutrient-specific.