Switching between foods is reliably associated with intake across eating events in children

Emerging evidence suggests switching between foods during an eating event is positively associated with intake. However, it is unclear whether switching is a stable behavior that predicts consumption across multiple eating events. The current study explored whether switching is consistent within children and reliably associated with intake across varied eating events. We analyzed data from 88 (45 F), 7-8-year-old children without obesity participating in a 7-visit prospective cohort study (ClinicalTrials.gov NCT03341247). Amount consumed and energy intake were measured at 4 separate meals of foods that varied by portion sizes served. Meals included macaroni and cheese, chicken nuggets, broccoli, and grapes (all 0.7-2.5 kcal/g). Children's intake was also assessed during 2 eating in the absence of hunger (EAH) paradigms separated by ≥ 1 year. The EAH paradigm included 9 sweet and savory snack foods (all 1.9-5.7 kcal/g). All eating events were video-recorded and switching was assessed by counting the number of times a child shifted between different food items. Results demonstrated that switching was reliably associated with intake at both the meals and the EAH paradigms (ps < 0.01). Specifically, at meals each additional switch was associated with 11.7 ± 1.3 kcal (7.7 ± 0.8 g) more consumed, and during EAH each additional switch was associated with 8.1 ± 2.1 kcal (2.1 ± 0.5 g) more consumed. Switching behavior was also moderately consistent across meals (ICC = 0.70) and EAH paradigms (ICC = 0.50). However, switching at meals was not related to switching at EAH paradigms. This study demonstrates the consistency of switching behavior and its reliable association with intake across eating events, highlighting its potential to contribute to chronic overconsumption and childhood obesity.

Child eating behaviors are consistently linked to intake across meals that vary in portion size

Prior studies evaluating a single meal in children characterized an "obesogenic" style of eating marked by larger bites and faster eating. It is unclear if this style is consistent across portion sizes within children so we examined eating behaviors in 91 children (7-8 years, 45 F) without obesity (BMI<90th percentile). Children consumed 4 ad libitum meals in the laboratory consisting of chicken nuggets, macaroni, grapes, and broccoli that varied in portion size (100%, 133%, 166%, 200%) with a maximum of 30 min allotted per meal. Anthropometrics were assessed using age and sex adjusted body mass index (BMI) percentile and dual energy x-ray absorptiometry. Bites, sips, active eating time, and meal duration were coded from meal videos; bite size (kcal and g/bite), proportion of active eating (active eating time/meal duration), and eating rate (kcal and g/meal duration) were computed. Intraclass correlation coefficients (ICC) showed that most eating behaviors were moderately consistent across portions (>0.50). The consistency of associations between eating behaviors and total meal intake and adiposity were assessed with general linear models adjusted for food liking, pre-meal fullness, age, and sex. Across all portions, more bites, faster eating rate, and longer meal duration were associated with greater intake. While higher BMI percentile was associated with faster eating rates across all meals, greater fat mass index was only associated with faster eating at meals with portions typical for children (i.e., 100% and 133%). In a primarily healthy weight sample, an 'obesogenic' style of eating was a consistent predictor of greater intake across meals that varied in portion size. The consistent relationship of these behaviors with intake makes them promising targets to reduce overconsumption.

Increased brain and behavioural susceptibility to portion size in children with loss of control eating

BACKGROUND

Portion size influences intake (i.e. the portion size effect [PSE]), yet determinants of susceptibility to the PSE are unclear.

OBJECTIVE

We tested whether children who reported an episode of loss of control (LOC) eating over the last 3 months would be more susceptible to the PSE and would show differential brain responses to food cues compared with children with no-LOC.

METHODS

Across five sessions, children (n = 47; 7-10 years) consumed four test meals at 100%, 133%, 167% and 200% conditions for portion size and completed a functional magnetic resonance imaging scan while viewing pictures of foods varied by portion size and energy density (ED). Incidence of LOC over the past 3 months was self-reported. Random coefficient models were tested for differences in the shape of the PSE curve by LOC status. A whole-brain analysis was conducted to determine response to food cues during the functional magnetic resonance imaging.

RESULTS

Reported LOC (n = 13) compared with no-LOC (n = 34) was associated with increased susceptibility to the PSE, as evidenced by a positive association with the linear slope (P < 0.005), and negative association with the quadratic slope (P < 0.05) of the intake curve. Children who reported LOC compared with no-LOC showed increased activation in the left cerebellum to small relative to large portions (P < 0.01) and right cerebellum to High-ED relative to Low-ED food cues (P < 0.01).

CONCLUSION

Children who reported LOC were more susceptible to the PSE and showed alterations in food-cue processing in the cerebellum, a hindbrain region implicated in satiety signalling.

Validation of the Diet Satisfaction Questionnaire: a new measure of satisfaction with diets for weight management

Objective

The Diet Satisfaction Questionnaire was developed to fill the need for a validated measure to evaluate satisfaction with weight‐management diets. This paper further develops the questionnaire, examining the factor structure of the original questionnaire, cross‐validating a revised version in a second sample and relating diet satisfaction to weight loss during a 1‐year trial.

Methods

The 45‐item Diet Satisfaction Questionnaire (DSat‐45) uses seven scales to assess characteristics that influence diet satisfaction: Healthy Lifestyle, Convenience, Cost, Family Dynamics, Preoccupation with Food, Negative Aspects, and Planning and Preparation. It was administered five times during a 1‐year weight‐loss trial (n = 186 women) and once as an online survey in a separate sample (n = 510 adults). Confirmatory factor analysis was used to assess and refine the DSat‐45 structure, and reliability and validity data were examined in both samples for the revised questionnaire, the DSat‐28. Associations were examined between both DSat questionnaires and weight loss in the trial.

Results

Internal consistency (reliability) was moderate for the DSat‐45. Confirmatory factor analysis showed improved fit for a five‐factor structure, resulting in the DSat‐28 that retained four of the original scales and a shortened fifth scale. This revised questionnaire was reliable in both samples. Weight loss across the year‐long trial was positively related to satisfaction with Healthy Lifestyle, Preoccupation with Food, and Planning and Preparation in both versions of the questionnaire.

Conclusions

Measures of reliability and validity were improved in the more concise DSat‐28 compared to the DSat‐45. This shorter measure should be used in future work to evaluate satisfaction with weight‐management diets.

Early predictors of weight loss in a 1-year behavioural weight-loss programme

Objective

Identifying early predictors of weight loss is key for developing personalized treatment. However, few individual factors have been identified that predict weight loss during intervention, other than early weight loss itself.

Methods

Women with overweight or obesity (n = 186, mean ± SD age 50.0 ± 10.6 years, body mass index 34.0 ± 4.2 kg m-2) participated in the Portion-Control Strategies Trial, a 1-year randomized controlled weight-loss trial with three intervention groups. Early changes in eating behaviours and psychological factors were evaluated by questionnaires at baseline and Month 1. The influence of these early changes on the trajectory of weight loss from baseline to Months 3 and 12 was assessed by random coefficients models.

Results

Although there were no differences in weight loss between intervention groups at the end of the trial, certain individual factors were shown to predict both early weight loss at Month 3 and longer-term weight loss at Month 12. Across all participants, increases in dietary restraint and healthy lifestyle ratings in the first month predicted more rapid weight loss from baseline to Month 3 (P < 0.05) and also predicted more rapid weight loss and slower regain from baseline to Month 12 (both P < 0.01). Early attendance and changes in disinhibition were not associated with subsequent weight loss.

Conclusions

Changes in psychological and behavioural measures, such as restraint, in the first month of weight loss intervention predicted longer-term weight loss in women. Early additional support or tailored treatment could promote long-term success by reinforcing these behaviours.

Dietary energy density: Applying behavioural science to weight management

Studies conducted by behavioural scientists show that energy density (kcal/g) provides effective guidance for healthy food choices to control intake and promote satiety. Energy density depends upon a number of dietary components, especially water (0 kcal/g) and fat (9 kcal/g). Increasing the proportion of water or water-rich ingredients, such as vegetables or fruit, lowers a food's energy density. A number of studies show that when the energy density of the diet is reduced, both adults and children spontaneously decrease their ad libitum energy intake. Other studies show that consuming a large volume of a low-energy-dense food such as soup, salad, or fruit as a first course preload can enhance satiety and reduce overall energy intake at a meal. Current evidence suggests that energy density influences intake through a complex interplay of cognitive, sensory, gastrointestinal, hormonal and neural influences. Other studies that focus on practical applications show how the strategic incorporation of foods lower in energy density into the diet allows people to eat satisfying portions while improving dietary patterns. This review discusses studies that have led to greater understanding of the importance of energy density for food intake regulation and weight management.

Does the incorporation of portion-control strategies in a behavioral program improve weight loss in a 1-year randomized controlled trial?

BACKGROUND/OBJECTIVES

Controlling food portion sizes can help reduce energy intake, but the effect of different portion-control methods on weight management is not known. In a 1-year randomized trial, we tested whether the efficacy of a behavioral weight-loss program was improved by incorporating either of the two portion-control strategies instead of standard advice about eating less.

SUBJECTS/METHODS

The Portion-Control Strategies Trial included 186 women with obesity (81%) or overweight (19%). Participants were randomly assigned to one of three equally intensive behavioral programs, consisting of 19 individual sessions over 12 months. The Standard Advice Group was instructed to eat less food while making healthy choices, the Portion Selection Group was instructed to choose portions based on the energy density using tools such as food scales and the Pre-portioned Foods Group was instructed to structure meals around pre-portioned foods such as single-serving main dishes, for which some vouchers were provided. In an intention-to-treat analysis, a mixed-effects model compared weight loss trajectories across 23 measurements; at month 12, weight was measured for 151 participants (81%).

RESULTS

The trajectories showed that the Pre-portioned Foods Group initially lost weight at a greater rate than the other two groups (P=0.021), but subsequently regained weight at a greater rate (P=0.0005). As a result, weight loss did not differ significantly across groups at month 6 (mean±s.e. 5.2±0.4 kg) or month 12 (4.5±0.5 kg). After 1 year, measured weight loss averaged 6% of baseline weight. The frequency of using portion-control strategies initially differed across groups, then declined over time and converged at months 6 and 12.

CONCLUSIONS

Incorporating instruction on portion-control strategies within a 1-year behavioral program did not lead to a greater weight loss than standard advice. Using pre-portioned foods enhanced early weight loss, but this was not sustained over time. Long-term maintenance of behavioral strategies to manage portions remains a challenge.

What is the role of portion control in weight management?

Systematic studies have shown that providing individuals with larger portions of foods and beverages leads to substantial increases in energy intake. The effect is sustained over weeks, supporting the possibility that large portions have a role in the development of obesity. The challenge is to find strategies to effectively manage the effects of portion size. One approach involves teaching people to select appropriate portions and to use tools that facilitate portion control. Although tools such as portion-control plates have been shown in several randomized trials to improve weight loss, limited data are available on whether education and tools lead to long-term changes in eating behavior and body weight. Another approach is to use preportioned foods (PPFs) to add structure to meals and minimize decisions about the amount of food to eat. A number of randomized controlled trials have demonstrated the efficacy of both liquid meal replacements and solid PPFs for weight loss and weight loss maintenance, but it is not known if they lead to better understanding of appropriate portions. Although portion control is important for weight management, urging people simply to 'eat less' of all foods may not be the best approach as high-energy-dense foods disproportionately increase energy intake compared with those lower in energy density. A more effective strategy may be to encourage people to increase the proportion of foods low in energy density in their diets while limiting portions of high-energy-dense foods. If people lower the energy density of their diet, they can eat satisfying portions while managing their body weight.

Retention rates and weight loss in a commercial weight loss program

OBJECTIVE

To evaluate and describe retention rates and weight loss in clients participating in a commercial weight loss program.

SUBJECTS

A total of 60 164 men and women ages 18-79 years who enrolled in the Jenny Craig Platinum program between May 2001 and May 2002.

METHODS

Retention rates, mean weight loss and percent weight loss were calculated on a weekly basis for the 52-week period following initial enrollment in the weight loss program. Clients were categorized based on final week of participation in the program (weeks 1-4, weeks 5-13, weeks 14-26, weeks 27-39 and weeks 40-52) and weight loss was calculated at final week. A subgroup of clients was identified based on attendance through 13, 26 and 52 weeks. Mean and percent weight loss was calculated for these subgroups of clients.

RESULTS

Of the 60 164 men and women who enrolled in the weight loss program, 73% were retained in the program after 4 weeks, 42% at 13 weeks, 22% at 26 weeks and 6.6% at 52 weeks. Clients who dropped out of the program during the first 4 weeks lost 1.1+/-1.6% (mean+/-s.d.) of their initial body weight, whereas clients who dropped out between 40 and 52 weeks lost 12.0+/-7.2%. Clients in the 13-week, 26-week and 52-week cohorts lost 8.3+/-3.3, 12.6+/-5.1 and 15.6+/-7.5% of their initial body weight, respectively.

CONCLUSION

Weight loss was greater among clients who were retained in the program longer. The findings from this study suggest that a commercial weight loss program can be an effective weight loss tool for individuals who remain active in the program.

Does nutrition information about the energy density of meals affect food intake in normal-weight women?

This study investigated whether the energy density of foods affected energy intake when subjects were informed about the energy density of their meals. Forty normal-weight women ate breakfast, lunch, and dinner in the laboratory on three separate days. The entrée at each meal was varied in energy density to be either 1.25, 1.50, or 1.75 kcal/g (5.23, 6.28, or 7.32 kJ/g), but was held similar in macronutrient composition and palatability. On each day, the entrées at all three meals had the same energy density. All entrées were consumed ad libitum. Subjects were assigned to one of two groups. Subjects in the information group received a nutrition label with each meal, which showed the energy density of the entrée. Subjects in the no-information group did not receive any nutrition information. The results revealed that subjects in both groups had the same pattern of food intake across the three levels of energy density. Energy density significantly affected energy intake; subjects in both groups combined consumed 22% less energy in the condition of low energy density than in the condition of high energy density (p < 0.0001). These findings show that energy density can have a significant influence on energy intake, even when individuals are informed about the energy density of their meals.

Dysfunctional eating in the eating disorders

Aberrant eating patterns in the eating disorders have been observed across various laboratory-based and clinical studies. It is now clear that problems in experiencing and expressing hunger, appetite, and satiety in anorexia and bulimia nervosa are likely to perpetuate the disorders once established. Whether problems in appetite regulation are primary or secondary to the development of the disorders is unknown. In studies examining indices of appetite regulation after treatment, there still remain significant levels of eating abnormality. This suggests that the main goals of treatment, including restoration of body weight in anorexia nervosa, abstaining from dieting in anorexia or bulimia nervosa, and reducing or abstaining from binge eating, do not correct some features of abnormal eating. The efficacy of nutritional counseling and specific nutritional management programs have been tested, and these seem to produce positive outcomes in improving eating behavior. Direct behavioral interventions to change eating patterns also have been examined, and these too seem to produce benefits that may be incorporated into CBT. Greater collaboration and cooperation between researchers and clinicians in addressing dysfunctional eating in the eating disorders will highlight improvements in treatment for identifiable eating abnormalities and will further the understanding of the human appetite system.

Energy density of foods affects energy intake across multiple levels of fat content in lean and obese women

BACKGROUND

The results of previous studies indicated that energy density, independent of fat content, influences energy intake. In most studies, however, both fat content and energy density were lower than in typical American diets.

OBJECTIVE

We examined the influence of energy density on intake when fat content was above, below, or similar to the amount of fat typically consumed and when energy density was closer to that of American diets.

DESIGN

Lean (n = 19) and obese (n = 17) women consumed all meals daily in our laboratory during 6 experimental sessions. The main entrées, consumed ad libitum, were formulated to vary in fat content (25%, 35%, and 45% of energy) and energy density (5.23 kJ/g, or low energy density, and 7.32 kJ/g, or high energy density) but to have similar palatability.

RESULTS

Energy density influenced energy intake across all fat contents in both lean and obese women (P < 0.0001). Women consumed less energy in the low (7531 kJ) than in the high (9414 kJ) energy density condition. Despite this 20% lower energy intake, there were only small differences in hunger (7%) and fullness (5%). Women consumed a similar volume, but not weight, of food daily across conditions. Differences in intake by weight, but not volume, occurred because for some versions of manipulated foods, weight and volume were not directly proportional.

CONCLUSIONS

Energy density affected energy intake across different fat contents and at levels of energy density comparable with those in typical diets. Furthermore, our findings suggest that cues related to the amount of food consumed have a greater influence on short-term intake than does the amount of energy consumed.

Short-term effects of a progestational contraceptive drug on food intake, resting energy expenditure, and body weight in young women

BACKGROUND

Studies showed that hormonal fluctuations that occur over the human menstrual cycle affect energy intake and expenditure. However, little is known about the possible effects on body weight regulation that may arise when these cyclic changes are suppressed with hormonal contraceptives.

OBJECTIVE

The aim of this study was to examine how a progestational contraceptive drug (depot medroxyprogesterone acetate) affects food intake, resting energy expenditure (REE), and body weight in young women.

DESIGN

Twenty normal-weight women were tested in a single-blind, placebo-controlled experiment. Body weight, REE, and 3-d food intake (food provided) were measured in the follicular and luteal phases of 2 menstrual cycles before a single injection of depot medroxyprogesterone or saline solution was administered. Measurements were also taken 4 times after injection: in the luteal and follicular phases of 2 cycles in the placebo group and 2 wk apart (to mimic timing of the menstrual phases) in the drug group.

RESULTS

Before injection, the phase of the menstrual cycle affected both energy intake and REE. The study participants consumed more energy (4.3%; P = 0.02) and expended more energy at rest (4.3%; P = 0.0002) in the luteal phase than in the follicular phase. Comparison of pre- and postinjection means showed that treatment with the contraceptive drug had no significant effects on energy intake, REE, or body weight.

CONCLUSIONS

This study showed that, although phases of the menstrual cycle affected energy intake and REE, depot medroxyprogesterone acetate did not alter energy intake or expenditure or cause weight gain in young women.

Effects of acute food deprivation on eating behavior in eating disorders

OBJECTIVE

Effects of acute food deprivation on eating behavior in bulimic patients and controls were investigated. It was predicted that food deprivation would increase overall food intake and result in overeating in bulimics.

METHOD

Following 19 hr of food deprivation (in which breakfast and lunch were skipped), or no deprivation, food intake was measured in 9 inpatients with anorexia nervosa (binge eating/purging subtype, ANB), 10 inpatient (BN/in) and 9 outpatient (BN/out) normal-weight bulimics, and 11 unrestrained and 10 restrained controls.

RESULTS

A general trend for increased food intake following deprivation was found. However, only BN/in patients consumed significantly more and selected higher energy foods following deprivation. ANB patients demonstrated the greatest degree of variability in intake and the least magnitude of change in ratings as a function of eating.

DISCUSSION

A period of acute food deprivation did not trigger marked eating pathology as evidenced by overconsumption. Chronic dietary restraint may be a more potent precipitating factor in overeating than absolute number of hours of food restriction.

Effects of dietary fat, nutrition labels, and repeated consumption on sensory-specific satiety

This study investigated whether energy from fat, nutrition information, and/or repeated consumption of a palatable snack food affects the development of sensory-specific satiety (SSS). Participants (51 males and 44 females) ate an afternoon snack of potato chips in a laboratory for two 10-day (Monday-Friday) sessions in a repeated measures, cross-over design. In one 10-day session, participants were given regular, full-fat potato chips (22.2 kJ/g; 150 kcal/oz) and, in the other, they were given potato chips made with olestra (11.8 kJ/g; 80 kcal/oz), a non-absorbable fat replacer. Information about the fat and energy content of the chips was provided to half the participants, while the other half was not informed. In both sessions, participants were instructed to consume the potato chips ad libitum. Initial ratings of sensory properties of the two types of chips did not differ significantly. In SSS tests, participants rated sensory properties of the chips and four test foods (turkey, strawberry yogurt, cookie, and carrot) on days 1, 5, and 10 of the 10-day sessions. Following consumption, ratings of pleasantness of taste and texture and prospective consumption of both types of chips declined compared to the test foods. Further analyses showed that the development of SSS was not affected by the fat and energy content of the chips, the provision of nutrition information, or repeated consumption.

Increasing the volume of a food by incorporating air affects satiety in men

BACKGROUND

Previous research indicated that increasing the volume of food by adding water can lead to reductions in energy intake. However, the addition of water affects not only the volume but also the energy density (kJ/g) of foods. No studies have examined the effect of volume independent of energy density on intake.

OBJECTIVE

We examined the effect of food volume independent of energy density on satiety.

DESIGN

In a within-subjects design, 28 lean men consumed breakfast, lunch, and dinner in the laboratory 1 d/wk for 4 wk. On 3 d, participants received a preload 30 min before lunch and on 1 d no preload was served. Preloads consisted of isoenergetic (2088 kJ), yogurt-based milk shakes that varied in volume (300, 450, and 600 mL) as a result of the incorporation of different amounts of air. Preloads contained identical ingredients and weighed the same.

RESULTS

The volume of the milk shake significantly affected energy intake at lunch (P < 0.04) such that intake was 12% lower after the 600-mL preload (2966 +/- 247 kJ) than after the 300-mL preload (3368 +/- 197 kJ). Subjects also reported greater reductions in hunger and greater increases in fullness after consumption of both the 450- and 600-mL preloads than after the 300-mL preload.

CONCLUSIONS

Changing the volume of a preload by incorporating air affected energy intake. Thus, the volume of a preload independent of its energy density can influence satiety.

Dietary approaches to the treatment of obesity

According to the National Institute of Health guidelines for the treatment of overweight and obesity, the most important element in a weight loss program is the reduction in energy intake. Reducing the fat content of the diet and increasing physical activity without restricting energy intake are relatively inefficient methods of weight loss. Because individuals tend to consume a constant weight of food, the decrease in energy intake on a reduced-fat diet is likely related to the lower energy density of the diet. Diets of low energy density, which are typically low in fat and rich in complex carbohydrates, allow individuals to consume satisfying portions of food while reducing their energy intake. Because a wide variety of foods can be included in a diet that is low in energy density, this type of diet encourages the adoption of life-long eating habits that are integral to the maintenance of weight loss and the prevention of weight gain.

The role of energy density in the overconsumption of fat

In recent years, research has focused on why fat is so readily overconsumed. Although the palatability of many high fat foods can encourage overconsumption, another possibility is that fat is not very satiating. A number of studies have compared the effects of fat and carbohydrate on both satiation (the amount eaten in a meal) and satiety (the effect on subsequent intake), but have found little difference between these macronutrients when the palatability and energy density were similar. On the other hand, the energy density of foods has been demonstrated to have a robust and significant effect on both satiety and satiation, independently of palatability and macronutrient content. It is likely that the high energy density of many high fat foods facilitates the overconsumption of fat. An understanding of the role that the energy density of foods plays in the regulation of food intake should lead to better dietary management of hunger and satiety in conditions associated with both over- and underconsumption of energy, such as obesity and anorexia.

Maintenance of dietary behavior change

Reducing dietary fat, saturated fat, and sodium and increasing intakes of dietary fiber and fruits and vegetables are important for cardiopulmonary risk reduction. Behaviorally, these dietary changes are very challenging, and in different ways. Fewer than half of U.S. adults have diets meeting recommended intakes of these constituents, and many do not see a need to align their diets with recommendations. Various nutrition education and behavioral counseling approaches have been shown to facilitate changes in fat, fiber, sodium, and fruits and vegetables, but primarily in research settings and among the highly motivated. Practice-based and interdisciplinary studies are needed to refine strategies to effect long-term dietary changes, to differentiate behavioral issues for changes involving additions versus deletions from the diet, and to elucidate the roles of sensory, psychosocial, and contextual factors in adoption and maintenance.

Comparative lipid and lipoprotein responses to solid-food diets and defined liquid-formula diets

BACKGROUND

Liquid-formula diets (LFDs) are useful in metabolic studies of the cholesterolemic effects of dietary lipids because they can be formulated with accuracy, facilitating precise delivery of fatty acids of interest. However, because of differences in composition and nutrient delivery between LFDs and solid-food diets (SFDs), there is a need to determine differences in their effects.

OBJECTIVE

Our objective was to compare lipid and lipoprotein responses to changes in total fat, saturated fatty acids (SFAs), and cholesterol in subjects consuming an SFD or LFD.

DESIGN

Twenty-one healthy subjects consumed controlled diets representative of an average American diet [AAD; 37% of energy from fat (15% from SFAs), and <50 mg cholesterol/MJ] or a National Cholesterol Education Program (NCEP) Step II diet [26% fat (5% from SFAs) and <25 mg cholesterol/MJ]. Other nutrients were similar between diets. Diets were consumed for 23 d in a randomized, crossover design.

RESULTS

For the AAD and NCEP Step II diet, there were no significant differences in lipids and apolipoproteins when the LFD or SFD versions were consumed. In contrast, consumption of the SFD was associated with significantly lower total cholesterol and triacylglycerols than was consumption of the corresponding AAD or Step II LFD (P < 0.05). Subjective ratings of satiety, hunger, and quality of life between diet forms did not differ significantly.

CONCLUSIONS

Both LFDs and SFDs yield quantitatively similar cholesterolemic responses to changes in dietary fat, SFAs, and cholesterol. LFDs may offer advantages because they provide easily administered, complete, balanced nutrition without affecting satiety.

Water incorporated into a food but not served with a food decreases energy intake in lean women

BACKGROUND

Previous research showed that decreasing the energy density (kJ/g) of foods by adding water to them can lead to reductions in energy intake. Few studies have examined how water consumed as a beverage affects food intake.

OBJECTIVE

This study examined the effects of water, both served with a food and incorporated into a food, on satiety.

DESIGN

In a within-subjects design, 24 lean women consumed breakfast, lunch, and dinner in our laboratory 1 d/wk for 4 wk. Subjects received 1 of 3 isoenergetic (1128 kJ) preloads 17 min before lunch on 3 d and no preload on 1 d. The preloads consisted of 1) chicken rice casserole, 2) chicken rice casserole served with a glass of water (356 g), and 3) chicken rice soup. The soup contained the same ingredients (type and amount) as the casserole that was served with water.

RESULTS

Decreasing the energy density of and increasing the volume of the preload by adding water to it significantly increased fullness and reduced hunger and subsequent energy intake at lunch. The equivalent amount of water served as a beverage with a food did not affect satiety. Energy intake at lunch was 1209 +/- 125 kJ after the soup compared with 1657 +/- 148 and 1639 +/- 148 kJ after the casserole with and without water, respectively. Subjects did not compensate at dinner for this reduction in lunch intake.

CONCLUSION

Consuming foods with a high water content more effectively reduced subsequent energy intake than did drinking water with food.

Energy density but not fat content of foods affected energy intake in lean and obese women

BACKGROUND

Studies have shown that energy intake increases when both the fat content and energy density of the entire diet increases. When the fat content and energy density vary independently of one another, however, energy density, but not fat content, influences intake.

OBJECTIVE

The present study examined whether energy intake in lean and obese women is affected when either the energy density or the fat content of a portion of the diet is manipulated and palatability is held constant.

DESIGN

In a within-subjects design, 17 lean and 17 obese women consumed meals in the laboratory for four, 4-d test periods. In 3 of these test periods the energy density (4.4 and 6.7 kJ/g) or the fat content (16% and 36% of energy) of compulsory entrees representing 50% of each subject's usual energy intake was manipulated. Additional self-selected foods were consumed ad libitum at meals and as snacks.

RESULTS

There were no systematic differences in palatability of the manipulated foods across conditions. Obese and lean participants responded similarly to the dietary manipulations. Intake of self-selected foods at meals was reduced significantly by 16% for both lean and obese subjects in the low- compared with the high-energy-density condition. The fat content of the compulsory foods had no significant effect on energy intake. Ratings of hunger did not differ between diets.

CONCLUSION

These results indicate that when a portion of the diet was manipulated, the energy density, but not the fat content, of the foods affected total energy intake at meals in both lean and obese women.

Do chemosensory changes influence food intake in the elderly?

Food intake declines with age, and elderly individuals frequently report a decrease in appetite. Changes in chemosensory systems may partially explain this low intake. However, few data have directly linked changes in gustatory or olfactory function to food choice or intake. In two studies, taste perception and preference were unrelated to sodium chloride or sugar intakes. Olfaction may be more affected by age than taste. Olfactory dysfunction is associated with decreased enjoyment of food, and adding odors to foods can increase intake in some elderly individuals. The consumption of a varied diet depends in part on sensory-specific satiety (a decrease in the pleasantness of a food as it is consumed). Sensory-specific satiety diminishes with age, and this could be part of the explanation of why some elderly individuals have little variety in their diets. However, the impact of chemosensory deficits on nutritional status depends on a number of social and environmental factors. For example, despite their age, financially secure, free-living healthy older men and women consumed more varied diets than young adults. Changes in mechanisms regulating food intake can make it difficult for some elderly individuals to maintain energy balance. When chemosensory impairments are combined with changes in food intake regulatory mechanisms, the risk for nutritional deficiencies may be high. If we are to optimize food intake and nutritional status in the elderly, additional basic studies on how changes in chemosensory systems associated with aging affect food selection and intake are required.

Intake of fat and carbohydrate: role of energy density

In this review, we consider two hypotheses which could explain why high-fat foods are overeaten. The first hypothesis is that fat is overeaten because it affects satiety and satiation less than carbohydrate. In several studies which have evaluated the effects of fat on satiety and satiation, fat differed little from carbohydrate when both the palatability and energy density of the test foods were matched. Therefore it is unlikely that the effects of fat on satiety or satiation provide the primary explanation for why it is overeaten. The second hypothesis is that the high energy density of fat facilitates its overconsumption. Support for this view comes from recent studies in which energy density significantly influenced intake when both the macronutrient content and palatability of the test foods were matched. For example, when individuals were fed diets varying in energy density and could eat as much food as they liked, they ate the same amount of food (by weight) so energy intake varied directly with energy density. Furthermore, when participants consumed foods of low energy density, they felt satisfied, despite reductions in energy intake. These findings show that energy density is a key determinant of energy intake in that cognitive, behavioral, and sensory cues related to the volume or weight of food consumed can interact with or override physiological cues associated with food intake.

Effect of fat-free potato chips with and without nutrition labels on fat and energy intakes

This study investigated the effect on fat and energy intakes of fat-free potato chips made with olestra compared with regular potato chips. Ninety-five participants (unrestrained and restrained males and females) were tested in 2 conditions. In the information condition, participants were given nutrition information about the chips and were aware that the chips differed in fat and energy contents. In the no-information condition, participants were not aware of the differences. In both conditions, participants ate either regular or fat-free potato chips ad libitum for an afternoon snack in a crossover design in two 10-d periods. To assess 24-h intake, participants completed food diaries twice in each 10-d period. The results showed that all groups significantly reduced their fat and energy intakes in the snack when eating the fat-free chips compared with the regular chips (P< 0.0001). Also, potato chip intake did not differ across time for either type of chip. Over 24 h all participants had lower fat intakes (P< 0.05) when eating the fat-free potato chips compared with the regular chips, but 24-h energy intake was not significantly different between groups. When information was provided, restrained participants ate more of the fat-free chips than the regular chips; however, this increase did not negate the reductions in fat and energy associated with eating the fat-free chips. This study showed that substituting fat-free (olestra-containing) potato chips for regular-fat chips can help reduce fat and energy intakes in short-term (within meal) situations and reduce fat intake over 24 h.

Volume of food consumed affects satiety in men

This study tested the hypothesis that the amount (weight or volume) of food consumed affects the satiating potency of a food, independent of its energy content. Normal-weight young men (n = 20) were tested in a within-subjects design. Subjects were served a milk-based drink or no drink (control), followed 30 min later by a self-selected lunch and > 4 h later by a self-selected dinner. Milk drinks were equal in energy content (2088 kJ, or 499 kcal) and had similar proportions of fat (30.3%), carbohydrate (54.7%), and protein (15%) across three volumes: 300, 450, and 600 mL. Ratings of palatability, sensory properties, and energy content of the drinks and of hunger completed before consumption of the preloads were not significantly different among conditions. The results showed that preload volume affected energy intake at lunch (P < or = 0.009) such that energy intake was less after the 600-mL preload than after the 300-mL preload. This effect was still present when energy intake at dinner was included (P < or = 0.022). At lunch, including energy from the preload, subjects overate relative to the control condition (4323 +/- 322 kJ) after the 300- (5263 +/- 321 kJ) and 450-mL (5011 +/- 300 kJ) preloads but not after the 600-mL (4703 +/- 353 kJ) preload. Thus, the best adjustment for the energy in the preloads was with the largest, least energy-dense drink. Consistent with the effects on intake, the volume of the drinks affected ratings of hunger and fullness. These results indicate that the volume consumed is an important determinant of satiety after milk drinks under these conditions.

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

OBJECTIVE

Severe obesity (ie, at least 100% overweight or body mass index > or =40 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.

Videotape assessment of changes in aberrant meal-time behaviors in anorexia nervosa after treatment

This study compared meal-time behaviors in patients with anorexia nervosa to normal-weight controls and the effects of hospital treatment on these behaviors. Ten restricting-anorexics and six normal-weight controls were given a standard lunch and asked to eat the entire meal. Their behaviors were recorded via hidden camera. All participants were tested twice--anorexics before and after in-patient treatment, and controls at similar intervals. Videotapes of these sessions were analysed for occurrence and duration of eight categories of non-ingestive behaviors: food manipulation, food preparation, food moving, non-food manipulation, concealment, vigilance, passivity and physical activity. Food-ingestion patterns, including number of bites of food and switches between different kinds of food, were also recorded. Results indicated that anorexics spent significantly more time than controls in behaviors that were directly food-related, and exhibited more vigilance behavior. Pre-treatment anorexics spent significantly more time in these behaviors than did post-treatment anorexics. Few group differences or treatment effects were found in food-ingestion patterns, although there was an indication that both pre- and post-treatment anorexics avoided high-fat foods more than controls did. These results suggest that videotaping provides a useful technique for characterizing the behavior associated with eating disorders. Further studies should explore whether normalization of these behaviors is associated with a positive clinical outcome.

Energy density of foods affects energy intake in normal-weight women

This study examined the effect of energy density, independent of fat content and palatability, on food and energy intakes. With use of a within-subjects design, normal-weight women (n = 18) were provided with meals for 2 d during each of three test sessions. During lunch, dinner, and an evening snack, subjects were given free access to a main entree varying in energy density (low, medium, or high). The manipulated main entrees were similar in palatability to their counterparts across conditions. Low-energy compulsory (consumption required) side dishes accompanied each meal. Subjects also consumed a standard, compulsory breakfast. Results showed that subjects consumed a similar amount of food (by weight) across the three conditions of energy density. Thus, significantly more energy was consumed in the condition of high energy density (7532 +/- 363 kJ, or 1800 +/- 86 kcal) than in the medium- (6356 +/- 281 kJ, or 1519 +/- 67 kcal) and low- (5756 +/- 178 kJ, or 1376 +/- 43 kcal) energy-density conditions (P < 0.0001). There were no differences in hunger or fullness before meals, after meals, or over the 2 d across conditions. The results from this study indicate that energy density affects energy intake independent of macronutrient content or palatability, suggesting that the overconsumption of high-fat foods may be due to their high energy density rather than to their fat content.

Sibutramine reduces food intake in non-dieting women with obesity

Sibutramine (SIB), an inhibitor of serotonin and noradrenaline reuptake, has been shown in clinical trials to be associated with a dose-related decrease in bodyweight. This double-blind, placebo-controlled, Latin square crossover study examined whether the effect on bodyweight could be due in part to a reduction in daily food intake. Twelve non-dieting, women with obesity (body mass index of 30.5 to 41.9) received three treatments (0 [matching placebo], 10, or 30 mg SIB/day) for 14 days, with 14-day washout periods in between. On days 7 and 14, participants came to the laboratory to eat breakfast, lunch, and dinner so that daily energy and macronutrient intakes and ratings of hunger and satiety could be measured. Significant reductions occurred in food intake (both grams and energy) over the 14-day study period. On day 7, SIB 30 reduced intake significantly by 1762 kJ (23% reduction from placebo), and on day 14, both SIB 10 and SIB 30 significantly reduced intake compared with placebo (SIB 10, 19% reduction [1490 kJ]; SIB 30, 26% reduction [2079 kJ]). On day 7, the percentage of energy consumed from carbohydrate increased significantly with the 30-mg dose (56.7%) compared with that of placebo (51.4%), with a reciprocal decrease in energy from fat (27.8% to 24%). The results show that SIB reduced energy intake in women with obesity who were not attempting to lose weight.

Effects of preloads of differing energy and macronutrient content on eating behavior in bulimia nervosa

Evidence suggests that bulimics demonstrate blunted satiety possibly due to repeated episodes of overeating. This suggestion was tested further by comparing responses to yogurt preloads differing in carbohydrate and fat relative to a lower energy control yogurt in 12 bulimics and 12 age- and weight-matched controls. Participants were tested on three occasions at lunchtime. On each occasion, appetite and mood were rated before and after receiving a lunch of raspberry yogurt (350 g). Covert manipulation of energy and nutrient content was achieved by matching the yogurts on sensory properties and formulating a control yogurt (161 kcal), a high-fat version (357 kcal: 65% calories from fat), and a high-carbohydrate version (357 kcal: 81% calories from carbohydrate). Although there were no differential effects of the preloads on intake of an ad libitum test meal given 5 hr later in either the control or bulimic groups, there were significant differences in test meal energy intake between groups. On average and with all conditions combined, bulimics ate significantly fewer calories (775 +/- 167 kcal) than controls (1182 +/- 94 kcal) and consumed a greater percentage of calories from carbohydrate than controls. Bulimics restricted their intake relative to controls, and chose foods low in fat. This study provides further evidence of restricted eating in bulimia nervosa when the opportunity to purge is not available. Furthermore, the present study suggests that intake by bulimics is not influenced by nutrient content per se but by consideration of the caloric value of foods and the consequences of eating certain foods for weight control.

Is the low-fat message giving people a license to eat more?

In the past decade, technology for modifying the fat content of foods has progressed and led to the development of highly palatable low-fat foods. Many Americans believe that weight loss can be accomplished by eating an ad libitum low-fat diet, and the development of highly palatable foods that are low in fat provides welcome additions to the food supply. However, in order to maintain high palatability, some of these foods have added sugars and other energy-bearing substances resulting in some low-fat foods which remain high in energy content and are energy-dense. Using such products as substitutes for higher-fat versions of foods is likely to bring about only small reductions in energy intake. A better strategy to reduce energy intake is to consume a low-fat diet made up of low-energy density foods such as fruits, vegetables, and other foods high in fiber and complex carbohydrates. Such a diet may include fat-replaced foods which are also reduced in energy since, for weight loss, a sustained reduction in energy intake is necessary. This can be best accomplished by eating a balanced diet not only low in fat content but also lower in energy.

Sensory properties of a nonabsorbable fat substitute did not affect regulation of energy intake

Many reduced-fat foods retain the sensory properties of their high-fat counterparts through the use of fat substitutes. This study examined whether regulation of energy intake is affected when the nonabsorbable fat substitute olestra is used to uncouple the sensory properties of fat from fat absorption and metabolism. Cream of broccoli soups were developed in three versions: fat-free, fat-free+olestra (33.3 g olestra), and high-fat (33.3 g fat) (923900 and 2150 kJ per serving, respectively). The olestra soup had the nutrient composition of the fat-free soup but the sensory properties of the high-fat soup. Subjects were grouped by sex, body weight, and dietary restraint (total n = 67). Subjects had either no preload (control) or a soup preload (465 g) followed by a self-selection lunch. Intake was measured at lunch, dinner, snack, and breakfast. At lunch, the response to the soup preloads was not affected by sex, dietary restraint, or body weight. Energy intake (soup+lunch) was significantly greater in the high-fat than in the control condition (P < 0.05), but energy intake in the fat-free and olestra-soup conditions was not significantly different from that in the control condition (3570, 3352, 3464, and 4457 kJ in control, fat-free, olestra, and high-fat soup conditions, respectively). Thus, subjects compensated completely for the energy in the fat-free and olestra soups but not for the energy in the high-fat soup. No differences were found in the response to the two fat-free conditions, one with the fatty taste and one without. In this study the sensory properties of fat alone, ie, apart from the physiologic effects of fat, did not affect energy regulation.

The Dietary Variety Score: assessing diet quality in healthy young and older adults

OBJECTIVE

To develop a new dietary variety score (DVS) and link it to other measures of diet quality, including a modified diet quality index (DQI).

SUBJECTS

The subjects were 24 healthy young (ages 20 to 30 years) and 24 healthy older (ages 60 to 75 years) adults, including 24 men and 24 women. Their dietary intake assessments were based on one 24-hour food recall interview and 14 consecutive days of food records.

DESIGN AND MEASURES

Energy and nutrient intakes were estimated using Nutritionist IV software. DVS was based on the cumulative number of different foods consumed over the 15-day period. DQI was a 5-point scale based on conformity with the key US dietary recommendations. Full score was awarded for diets deriving 30% or less of energy from fat, 10% or less of energy from saturated fat, more than 50% of energy from carbohydrate, and containing less than 300 mg cholesterol and 2,400 mg sodium per day. Analytic measures included analyses of variance, correlation analyses, and chi 2 tests.

RESULTS

Older subjects consumed more varied diets than did young subjects. Higher DVS values were linked positively to vitamin C intakes and negatively to the consumption of salt, sugar, and saturated fat. However, a high DVS was not linked to a high score on the DQI in this subject sample.

DISCUSSION/CONCLUSIONS

Few studies have addressed the issue of how many different foods constitute a varied diet. The present classification scheme offers a new way of assessing dietary variety at the individual or group level. Measures of dietary variety may represent an additional facet of diet quality and their relationship to selected health outcomes should be examined further.

Changes in food intake in response to stress in men and women: psychological factors

The relationship between psychological factors and changes in food intake during stress (both during a specific experience and during stress, in general) in 49 men, ages 18 to 34, and 52 women, ages 18 to 35, was assessed using questionnaires. Participants completed the State-Trait Anxiety Inventory, the Eating Inventory (which includes scales for disinhibition, cognitive restraint and perceived hunger) the Restraint Scale, the Eating Attitudes Test and the Binge Scale; and reported their height and weight. Men and women were divided into two groups regarding changes in eating habits during stress: increased intake and no increased intake. There were no significant differences between genders in the proportions of participants in each group. However, correlational analyses revealed different patterns of associations for males and females. For females, high scores on disinhibition were significantly correlated with eating more than usual during a specific stressful experience (r = 0.51, p < 0.001) as well as during stress, in general (r = 0.66, p < 0.001), while high scores on cognitive restraint were not. For males, neither disinhibition nor cognitive restraint were associated with the relationship between eating and stress. Scores on disinhibition discriminated over 80% of females who reported increased intake during stress from those who reported no increased intake. In females, the inability to maintain control of self-imposed rules concerning food intake is an important factor in the relationship between stress and eating.

Improved eating behavior in eating-disordered inpatients after treatment: documentation in a naturalistic setting

OBJECTIVE

Abnormalities of eating behavior are definitional components of eating disorders (ED), but are seldom observed directly. This study assessed abnormalities of eating behavior in ED patients before treatment and documented changes after multidisciplinary treatment.

METHOD

Thirty-three ED patients (13 ANR, 10 ANB, 10 BN) and 10 controls selected a lunch meal in a cafeteria before and after treatment with energy intake (kilocalories) and macronutrients covertly observed. Visual analog scales (VAS) measured hunger and satiety.

RESULTS

Before treatment, all ED patient groups experienced low hunger and high fullness, compared to controls. After treatment, hunger increased and satiety decreased. ANR patients, after treatment, increased energy intake from 366 to 916.5 kcal (p < .001), while BN patients increased from 409.9 to 663 kcal (p = .03). ANB nonsignificantly increased. ANR chose significantly more fats (22.7% to 36.2%, p = .05).

DISCUSSION

Treatment partially normalizes pre-meal hunger and satiety in ED patients and significantly improves eating behavior (total energy intake and fat content) in ANR and BN patients. Reasons for nonsignificant changes in ANB are not obvious. We recommend documentation of eating behavior by simple, inexpensive, observational methods in a naturalistic setting before and after treatment of ED patients.

Salt taste perceptions and preferences are unrelated to sodium consumption in healthy older adults

OBJECTIVE

Age-related deficits in salt taste perception are said to increase preferences for salty foods, thereby leading potentially to greater sodium consumption. This study examined the link between salt taste perceptions and preferences and sodium intakes as a function of age and gender.

DESIGN

We studied 24 young adults (aged 20 to 30 years) and 24 healthy older adults (aged 60 to 75 years). The subjects tasted and rated five sodium chloride solutions and eight samples of salted chicken broth containing from 0.04 to 0.64 mol/L sodium. Food intakes were assessed using a 24-hour food recall and 14 consecutive days of diet records.

RESULTS

Older and younger subjects did not differ in their sensory evaluations of chicken broth, including ratings of the intensity of saltiness. Older subjects preferred less salty soups than did young adults. Hedonic response profiles for salt in soup were not related to daily sodium intakes as assessed by diet records.

APPLICATIONS

Salt taste perceptions and preferences were unrelated to sodium intakes in young adults and in older respondents. Factors other than taste may influence dietary sodium consumption.

Food preferences and desire to eat in anorexia and bulimia nervosa

OBJECTIVE

To determine whether eating disordered patients and controls differ in visual analog scale (VAS) ratings of liking and desire to eat various foods and whether ratings differ according to caloric or macronutrient content of the foods.

METHOD

Fifty-five female inpatients with eating disorders and 15 controls rated their liking of and desire to eat 50 common foods at admission and discharge using 100-mm VAS.

RESULTS

All patient groups rated their desire to eat high-calorie foods significantly lower than their desire to eat low-calorie foods whereas controls rated their desire to eat high- and low-calorie foods equally. Patients also differed from controls more in ratings of desire to eat than in liking when foods were classified according to macronutrient content. In restricting anorexics (N = 25), ratings of liking and desire to eat for high-fat/low-carbohydrate (CHO) and high-fat/high-CHO foods were not significantly correlated at admission. Disparity in correlations between restrictors, bulimics (N = 18), and controls was attenuated with treatment while anorexics with bulimic features (N = 12) became less like controls from admission to discharge.

DISCUSSION

Differences in the way patients and controls perceive foods should be borne in mind during the treatment process. Furthermore, since patients had not completely normalized by discharge, treatment strategies should emphasize acceptance of foods varying in macronutrient and caloric content, as intake of a varied diet is of key importance in regaining and maintaining good health.

Age-related impairments in the regulation of food intake

Low food intake in elderly individuals increases the risk for many nutrition-related acute or chronic illnesses. It is not known whether aging is associated with changes in hunger and satiety, or whether elderly individuals can regulate energy intake in response to manipulations of the energy or nutrient content of foods. Therefore, this study investigated short-term energy regulation in healthy elderly (n = 16; aged 60-84 y) and young (n = 16; aged 18-35 y) men. Participants were given yogurt preloads that varied in energy and macronutrient content (low-fat, low-energy, 962 kJ; high-fat, high-energy, 2134 kJ; high-carbohydrate, high-energy 2134 kJ), or no yogurt, followed by a self-selected lunch (presented 30 min after subjects began to consume the yogurt). Energy intake, the percentage of macronutrients consumed in the meals, and subjective sensations of hunger and satiety were analyzed. The elderly men consumed significantly less energy than the young men in the baseline (no yogurt) condition. Lower intake was concordant with subjective sensations of satiety; visual analog data indicated that the older men were less hungry and more full at the start of lunch. Compensation for energy in the preloads was less precise in the elderly than in the young men, in that elderly men consistently overate at the self-selected lunch. Young men consumed +/- 10% total energy (lunch + yogurt) in the yogurt preload conditions compared with their baseline intake; elderly men overate between 10% and 30% in relation to their baseline intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Fat, carbohydrate, and the regulation of energy intake

High-fat foods are readily overeaten. This could be because fat increases the palatability and energy density of foods or because fat has a low satiety value compared with carbohydrate. In several studies examining the effects of preloads that varied in fat and carbohydrate content on subsequent food intake, there was little difference in the effects of fat and carbohydrate on satiety. A dose-response preloading paradigm gives the most sensitive index of satiety. In one such test it was found that the effects of yogurts varying in fat or carbohydrate content did not differ in normal-weight, unrestrained men. However, in obese individuals or those concerned with body weight, fat in the yogurts was less effective in reducing subsequent food intake than carbohydrate. More studies are required to determine whether this small, but significant, insensitivity to energy from fat affects the regulation of food intake and body weight.

Information about the fat content of preloads influences energy intake in healthy women

OBJECTIVE

This study tested the hypothesis that the perceived fat content of a preload (a required first course) influences subsequent food and energy intake.

SUBJECTS AND DESIGN

Forty-eight healthy, nondieting women (24 restrained, 24 unrestrained) were given a fixed amount (350 g) of three different yogurts (low-fat, low-calorie; low-fat, high-calorie; high-fat, high-calorie), or no yogurt, followed by lunch (30 minutes after the yogurt preload was served) and dinner (4.5 hours later). Each subject was tested in all four conditions in a counterbalanced design. Half of the subjects received accurate information, in the form of a label, about the fat content of the yogurts, which did not necessarily correspond to energy content; the other half received no information.

ANALYSES

Energy intake, the percentage of macronutrients in the meals, and subjective sensations of hunger and satiety were analyzed.

RESULTS

No effect of restraint was noted in the intake analyses. A significant information-by-preload interaction (P < .05) was found. Subjects who had information consumed more energy at lunch after eating a preload labeled low fat than after eating a preload with similar energy content but labeled high fat. The opposite response was seen in women who did not receive information. When energy consumed at dinner was included in the analyses, overall intake was still significantly greater in the women who received information and ate a low-fat preload. No differences were found in the percentage of macronutrients selected or in subjective sensations after consumption of any of the preloads.

CONCLUSIONS

Messages about the fat content of a food can influence energy intake in healthy women.

Olfactory dysfunction in anorexia and bulimia nervosa

Fifty-five eating-disordered women and 16 normal controls participated in this study to determine whether olfactory function is altered in patients with food-restricting anorexia, anorexia with bulimic features, and bulimia nervosa. Olfactory function was assessed using the University of Pennsylvania Smell Identification Test and by determining phenyl ethyl alcohol odor detection thresholds. Only the very low-weight anorexics showed impairments in their identification and detection of odors. This group's olfactory function did not improve from admission to discharge despite significant weight gain. Although, overall, smoking had only a minor influence on olfactory function, the very low-weight anorexic smokers had the lowest scores of all subjects. Since higher-weight anorexics did not show such impairments, the results suggest that the severe and prolonged starvation experienced by the very low-weight anorexics caused or contributed to intractable deficits in the olfactory system and that these deficits are compounded by smoking.

Accurate energy compensation for intragastric and oral nutrients in lean males

Lean healthy males received either parenteral or enteral infusions of pure fat or carbohydrate (2092 kJ), or isotonic saline, to determine their influences on food intake and energy regulation in self-selected lunch and dinner meals. In the first study, six males received intravenous infusions for 3.5 h in the morning, followed by lunch 30 min after the infusion ended and dinner 6 h later. No compensation was seen for energy differences in intravenous infusions. In the second study, six males received intragastric infusions for 15 min or 3.5 h. Rapid intragastric infusions of fat or carbohydrate and slow infusions of fat significantly reduced intake at lunch, whereas slow carbohydrate infusions did not. In both studies, subjects reduced intake at lunch 30 min after 2092-kJ yogurt preloads varying in fat and carbohydrate, demonstrating their ability to respond to orally derived energy. These results support the existence of mechanisms in the gastrointestinal tract for the rapid detection of the energy content of ingested nutrients or foods in lean males.

Carbohydrates, fats, and satiety

The macronutrient composition of the diet can influence hunger, satiety, food intake, body weight, and body composition. Fat, not carbohydrate, is the macronutrient associated with overeating and obesity. Fat is overeaten because it is highly palatable and because it provides a high level of energy in a given volume of food. However, when given in equal volumes, carbohydrate (sugar) and fat have similar effects on hunger, satiety, and subsequent food intake when infused intragastrically or ingested in foods by normal-weight, unrestrained young men. In obese and restrained subjects, preloads of high-carbohydrate yogurts suppress subsequent food intake more than do high-fat yogurts, indicating a relative insensitivity to the satiety value of fat. Both the amount of fat in the diet and total energy intake should be managed in weight-loss regimens. Low-fat foods and fat substitutes can help to reduce fat intake. Although more data are required, currently the best dietary advice for weight maintenance and for controlling hunger is to consume a low-fat, high-carbohydrate diet with a high fiber content.

Effect of meal macronutrient and energy content on human performance

The effects of planned meals, varying in carbohydrate (CHO), fat and caloric content, on psychomotor performance by male subjects with unrestricted access to commercially-available foods was investigated in two residential studies. In the first study, two groups of three subjects (n = 6) completed psychomotor tasks before and after consuming a lunch consisting of 431 or 844 kcal, with caloric differences produced through covert changes in either fat or CHO content. The effects of each of four lunch conditions (low-fat, high-fat, low-CHO, high-CHO) were determined for three consecutive days. In the second study, two groups of three subjects (n = 6) received breakfast, lunch and an afternoon snack and completed psychomotor tasks after breakfast and lunch. Cumulative caloric content of the three eating occasions was approximately 700, 1200 or 1700 kcal (low, medium or high), again with differences resulting from covert changes primarily in either fat or CHO content. The effects of each of six food conditions were determined for two consecutive days. While changes in some aspects of performance were altered after meals, the effects were not related to the CHO, fat or caloric content of the meal. When subjects have unrestricted access to commercially-available foods, neither calories nor the relative fat or CHO content of normal meals influence human psychomotor task performance.

Satiety after preloads with different amounts of fat and carbohydrate: implications for obesity

High intake of dietary fat may be key in both the etiology and maintenance of obesity. Because a reduction in the proportion of energy derived from fat will be accompanied by an increase in the proportion of energy derived from carbohydrate, this study compared the effects of these macronutrients on eating behavior in obese and lean individuals. The effects of different amounts of fat and carbohydrate, covertly incorporated into yogurt preloads, on subsequent food intake, hunger, and satiety were assessed. A group of 12 normal-weight men, unconcerned about eating and body weight (unrestrained), accurately compensated for the energy in the preloads regardless of the nutrient composition. Other groups (n = 12 per group), including normal-weight restrained men and normal-weight and obese restrained and unrestrained females, did not show such orderly energy compensation; joule-for-joule, the high-fat preloads suppressed intake at lunch less than did high-carbohydrate preloads. These results suggest that a relative insensitivity to the satiating effect of fat could be involved in the development and maintenance of obesity.