Lack of compensation of energy intake explains the success of alternate day feeding to produce weight loss

BACKGROUND AND AIMS

This study was designed to obtain daily weighed food intake of participants engaged in Alternate Day Feeding (ADF). Prior ADF studies have used self-reported food intake, a method that has received criticism for its limited accuracy.

SUBJECTS AND METHODS

Forty-nine university students received academic credit for participating in the study. Following a 10-day baseline period, participants underwent ADF for the next 8 days. Restricted daily intake to ∼ 75% of baseline food intake levels was followed by ad libitum intake on alternate days. Food intake was weighed before and after each meal. Daily body weight was also tracked.

INTERVENTION

After the baseline period, participants underwent 8 days of ADF during which they consumed ∼ 75% of baseline energy intake by weight followed by ad libitum intake on alternate days. The trial concluded with 2 additional days of ad libitum feeding, for a total study duration of 10 days.

RESULTS

Daily food intake was constant during the baseline period (slope = -0.93 g/d, p = 0.56), and did not differ significantly (995 g (95% CI [752, 1198]) from the total consumed on ad libitum ADF days (951 g (95% CI [777, 1227]). Intake on ad libitum days did not show a trend to increase during the intervention. Body weight declined significantly during ADF.

CONCLUSIONS

ADF produces significant weight loss because food intake does not increase on ad libitum feeding days to compensate for reduced intake on restricted energy days. Data are consistent with prior work that suggests humans do not fully compensate for imposed deficits in energy intake.

The Rise and Fall of Physiological Theories of the Control of Human Eating Behavior

Kuhns was the first to suggest that theories in science do not develop in small increments but rather in major leaps to paradigms that examine the same question through very different perspectives. Theories on the mechanism responsible for control of human food intake fall into Kuhn’s description. This article describes how the two major theories of the control of food intake in humans, the Glucostatic Theory, and the Lipostatic Theory, showed initial promise as explanations, but later deteriorated with the slow accumulation experimental data. The locus of theories considered eating behavior as a part of physiological system that regulates the storage of energy on the body. We challenge this fundamental belief with data which suggests that we must be ready to accept a major change in the way we think about eating behavior if we are ever to decrease the prevalence of obesity.

Methodological Challenges in Estimating the Lifetime Medical Care Cost Externality of Obesity

There is a great deal of variability in estimates of the lifetime medical care cost externality of obesity, partly due to a lack of transparency in the methodology behind these cost models. Several important factors must be considered in producing the best possible estimate, including age-related weight gain, differential life expectancy, identifiability, and cost model selection. In particular, age-related weight gain represents an important new component to recent cost estimates. Without accounting for age-related weight gain, a study relies on the untenable assumption that people remain the same weight throughout their lives, leading to a fundamental misunderstanding of the evolution and development of the obesity crisis. This study seeks to inform future researchers on the best methods and data available both to estimate age-related weight gain and to accurately and consistently estimate obesity's lifetime external medical care costs. This should help both to create a more standardized approach to cost estimation as well as encourage more transparency between all parties interested in the question of obesity's lifetime cost and, ultimately, evaluating the benefits and costs of interventions targeting obesity at various points in the life course.

The daily Self-Weighing for Obesity Management in Primary Care Study: Rationale, design and methodology

Background Daily self-weighing (DSW) may be an effective harm-reduction intervention to disrupt continued weight gain. Self-Weighing for Obesity Management in Primary Care (SWOP) is a 24-month randomized controlled trial in 400 adults with obesity (BMI: kg/m² ≥ 30) receiving primary care through a clinical network affiliated with an academic medical center. Objective To test DSW as a potentially scalable way to deter age-related weight gain among primary care patients with obesity. Methods Randomized-controlled trial with two conditions: DSW (instruction to weigh daily and provision of a web-enabled digital scale with graphical weight feedback) or Standard Care (receive a monetary gift card equivalent to value of the scale). Both groups receive standardized weight management educational material. SWOP will test the causal effect of assignment to DSW (Aim 1) and adherence to DSW (Aim 2) on weight (primary outcome) and adoption of weight management practices (secondary outcomes), as well as evaluate the cost-effectiveness of DSW compared to standard care (Aim 3). Findings may inform clinical guidelines for weight management by providing evidence that DSW attenuates continued age-related weight gain among adults with obesity. This trial is registered with ClinicalTrials.gov (NCT04044794).

Self-Weighing and Visual Feedback Facilitates Self-Directed Learning in Adults Who Are Overweight and Obese

OBJECTIVE

Understanding how and why self-weighing works for some individuals but not others in weight management is vital. This study investigated how self-weighing and tracking of weight using a Web site facilitated a self-directed learning process in overweight or obese adults interested in losing weight.

DESIGN

Semistructured interviews with study completers (n = 47) and voluntary withdrawals (n = 10) about their experience after 6 and 12 months of using the program or when they withdrew.

ANALYSIS

Qualitative, guided by self-directed learning theory.

RESULTS

Although both completers and those who withdrew engaged in self-directed learning, often exemplifying the same concepts (eg, instrumental learning), experiences described a positive sense of control over weight in completers and a lack of sense of control in those who withdrew.

CONCLUSIONS AND IMPLICATIONS

Overall, it seemed that frequent self-weighing and visual feedback of body weight over time facilitated a self-directed learning process in both completers and those who withdrew. This research provides a rich understanding of how adults use self-weighing to facilitate self-directed learning for weight loss. Future studies assessing how self-weighing and visual displays of weight facilitate a self-directed learning process in diverse populations and age groups are necessary to better understand how self-weighing works and for whom self-weighing is beneficial.

Predicted Lifetime Third-Party Costs of Obesity for Black and White Adolescents with Race-Specific Age-Related Weight Gain

OBJECTIVE

There exists enormous variation in estimates of the lifetime cost of adolescent obesity by race. To justify policy measures to reduce obesity rates nationally in this demographic, the costs of obesity in late adolescence must first be discerned. Although several researchers have sought to quantify obesity's true cost, none has accounted for race-specific age-related weight gain, a vital component in producing an accurate estimate.

METHODS

This paper employs a Markov model of BMI category state changes separately for black and white males and females from age 18 to 75 applied to updated estimates of obesity's costs and effect on mortality to quantify the median lifetime cost of obesity at age 18.

RESULTS

This study found lower lifetime costs than previously, largely because of the dramatic gain in weight among normal-weight individuals, particularly black males, that occurs in early adulthood.

CONCLUSIONS

A substantial portion of obesity's prevalence, and therefore cost, for black males and females comes from age-related weight gain in early adulthood. This speaks to the persistent threat of obesity beyond adolescence for this demographic, and further research should focus on whether policy can modify the behaviors and environment through which and in which this sharp increase in weight occurs.

Quantifying the imprecision of energy intake of humans to compensate for imposed energetic errors: A challenge to the physiological control of human food intake

To assess the precision of the biological control of energy intake we performed a systematic review of studies that measured acute changes in human food intake in response to energetic errors. The imposed errors were grouped into the following categories of studies: alternate day fasting, changes in diet composition, exercise, meal skipping, overfeeding, energy substitutes, underfeeding and changes in portion size. Seven hundred thirty-nine studies published between 1980 and 2017 were identified from which the data from 592 groups from 200 studies were extracted and subjected to analysis consisting of a total of 13,203 participants. For each category of imposing an energetic error, an Energetic Error was calculated as (Observed Mean Energy Intake - Expected Mean Energy Intake)/Expected Mean Energy Intake. In no category of studies was the Energetic Error equal to zero. In studies where participants were expected to increase energy intake, the increase was not sufficient to overcome the deficit. Similarly, in studies where a reduction in energy intake was expected, the reduction was insufficient to restore energy balance to zero. The average energetic error resulting from imposed energetic challenges is about twenty-four percent, a value sufficiently large to account for the increase in body weight observed in the U.S. population over the past 50 years.

Frequent Self-Weighing with Electronic Graphic Feedback to Prevent Age-Related Weight Gain in Young Adults

OBJECTIVE

An intervention using Wi-Fi scales and graphic e-mail feedback, the caloric titration method (CTM), to reduce age-related weight gain over 1 year among college students was evaluated.

METHODS

First-year college students (n = 167) were randomized to CTM or control (C) groups and provided Wi-Fi scales. The CTM group was instructed to weigh daily, view a weight graph e-mailed to them after weighing, and try to maintain their weight. The C group could weigh at any time but did not receive feedback. At 6 months and 1 year, the C group provided weights. For intention to treat analysis, an adjusted mixed model was used to analyze the effect of the intervention.

RESULTS

Baseline body mass index was 22.9 ± 3.0 kg/m(2) . Ninety-five percent of the CTM participants weighed ≥ 3 times/week, compared to 15% in the C group (P < 0.001). After 1 year, the C group had gained 1.1 ± .4 kg whereas the CTM group lost 0.5 ± 3.7 kg (F = 3.39, P = 0.035). The difference in weight change between the two groups at 1 year was significant (P = 0.004). Retention was 81%.

CONCLUSIONS

CTM intervention was effective in preventing age-related weight gain in young adults over 1 year and thus offers promise to reduce overweight and obesity.

Does measuring body weight impact subsequent response to eating behavior questions?

OBJECTIVES

If being weighed impacts perceptions of eating behavior, it is important that the order of questionnaires and weighing be considered in research and practice. A quasi-experimental study was performed to examine whether being weighed immediately prior to completing a questionnaire affects responses to eating behavior questions. It was hypothesized that being weighed would serve as a priming stimulus and increase measures of dietary restraint, disinhibition, and hunger.

METHODS

Trained researchers collected a sample of volunteers (n = 355) in 8 locations in the United States on two Saturdays in the summer of 2011. Half of the participants were weighed immediately prior to completing the Three Factor Eating Questionnaire (TFEQ), with the remaining half weighed immediately after TFEQ completion.

RESULTS

A priori hypotheses were not supported despite replicating known relationships between weight, dietary restraint and disinhibition. Results indicated that being weighed first produced a difference in differences on disinhibition scores between low restraint score (95% CI = 4.65-6.02) and high restraint score (95% CI = 6.11-7.57) compared to being weighed after questionnaire completion (p = 0.003). However, this relationship was not significant when modeling restraint as a continuous variable, questioning the use of dichotomization.

CONCLUSIONS

Being weighed is unlikely to be a strong enough prime to significantly change scores on eating behavior questionnaires for everyone, but may allow differences in restraint status to become more evident. Researchers assessing dietary restraint should be wary of the possibility of producing different results when treating restraint as continuous or dichotomous, which could lead to different interpretations.

Frequent Self-Weighing and Visual Feedback for Weight Loss in Overweight Adults

Evidence has suggested that self-weighing may be beneficial for weight control in adults, but few studies have independently assessed the contribution of this behavior to weight loss. This study experimentally tested daily self-weighing and visual feedback (the Caloric Titration Method (CTM)) as a weight loss and weight loss maintenance intervention over 2 years. 162 overweight individuals were randomized to the CTM intervention or delayed treatment control group. In year 1, weight change was compared between groups, and in year 2, the control group started using the CTM while the intervention group continued using the CTM for maintenance. A significant difference in weight loss over the first year (CTM n = 70; 2.6 ± 5.9 kg versus control n = 65; 0.5 ± 4.4 kg, p = 0.019) was qualified by a group × gender × time interaction (p = 0.002) such that men lost more weight using the CTM. In year 2, the CTM group maintained their weight and the control group lost an amount similar to the intervention group in year 1. Daily self-weighing and visual feedback facilitated a minimal amount of weight loss and maintenance of this loss. Future research investigating characteristics of those who benefit from this type of self-directed intervention is warranted.

Daily Self-Weighing to Control Body Weight in Adults: A Critical Review of the Literature

The objective of this study is to review the history of daily self-weighing for weight control, discuss the possibility that self-weighing may cause adverse psychological symptoms, and propose mechanisms that explain how self-weighing facilitates weight control. A systematic forward (citation) tracking approach has been employed in this study. In the early literature, experimental tests did not demonstrate a benefit of adding daily self-weighing to traditional behavioral modification for weight loss. More recent studies have shown that daily self-weighing combined with personalized electronic feedback can produce and sustain weight loss with and without a traditional weight loss program. Daily self-weighing appears to be effective in preventing age-related weight gain. Apart from these experimental findings, there is considerable agreement that the frequency of self-weighing correlates with success in losing weight and sustaining the weight loss. The early literature suggested frequent self-weighing may be associated with negative psychological effects. However, more recent experimental trials do not substantiate such a causal relationship. In conclusion, daily self-weighing may be a useful strategy for certain adults to prevent weight gain, lose weight, or prevent weight regain after loss. More research is needed to better understand the role of different types of feedback, who benefits most from self-weighing, and at what frequency.

Number of foods available at a meal determines the amount consumed

The number of foods available at a meal has been suggested as a major determinant of the amount consumed. Two studies conducted in humans test this idea by altering the number of foods available at a meal where participants eat the available foods ad libitum. In Study 1, dinner intake of twenty-seven young adults was measured. The amount consumed was measured when subjects were served either: (a) a composite meal (a protein rich food, a carbohydrate rich food, and a vegetable), (b) a low carbohydrate meal (protein rich food and vegetable), or (c) a vegetarian meal (carbohydrate rich food and vegetable). In Study 2, twenty-four subjects were given two different meals presented either as individual foods or as a composite meal (stir-fry or stew). Both studies show that the greater the number of foods offered at a meal, the greater the total intake. Study 2 demonstrated that the effects observed in Study 1 could not be attributed to different nutrient compositions, but was rather due to the presentation of the individual foods because the same foods that were offered as individual foods were combined to make the composite meal. The results demonstrate that the greater the number of foods offered at a meal, the greater the spontaneous intake of those foods. This finding is important because not only does it expand the concept of variety from the kinds of foods to the number of foods, but it presents an environmental variable that might contribute to overeating and obesity.

Set points, settling points and some alternative models: theoretical options to understand how genes and environments combine to regulate body adiposity

The close correspondence between energy intake and expenditure over prolonged time periods, coupled with an apparent protection of the level of body adiposity in the face of perturbations of energy balance, has led to the idea that body fatness is regulated via mechanisms that control intake and energy expenditure. Two models have dominated the discussion of how this regulation might take place. The set point model is rooted in physiology, genetics and molecular biology, and suggests that there is an active feedback mechanism linking adipose tissue (stored energy) to intake and expenditure via a set point, presumably encoded in the brain. This model is consistent with many of the biological aspects of energy balance, but struggles to explain the many significant environmental and social influences on obesity, food intake and physical activity. More importantly, the set point model does not effectively explain the 'obesity epidemic'--the large increase in body weight and adiposity of a large proportion of individuals in many countries since the 1980s. An alternative model, called the settling point model, is based on the idea that there is passive feedback between the size of the body stores and aspects of expenditure. This model accommodates many of the social and environmental characteristics of energy balance, but struggles to explain some of the biological and genetic aspects. The shortcomings of these two models reflect their failure to address the gene-by-environment interactions that dominate the regulation of body weight. We discuss two additional models--the general intake model and the dual intervention point model--that address this issue and might offer better ways to understand how body fatness is controlled.

Losing weight without dieting. Use of commercial foods as meal replacements for lunch produces an extended energy deficit

High-protein liquid meal replacements have proven to be effective in reducing caloric intake and body weight. Recently, substituting high fiber breakfast cereals for the more expensive high-protein drinks has been found to be equally effective to reduce weight. The following study tested the hypothesis that the mechanism responsible for the reduced intake was not the dietary composition of the meal replacement, but the controlled portion sized meals. Seventeen volunteers ate all of their meals and snacks from foods provided by the research unit from Monday to Friday for five consecutive weeks. For the first week, all participants selected their food from a buffet where each food was weighed before and after eating. For the next two weeks, half of the group selected their lunch by choosing one food from a selection of six commercially available portion controlled foods. They could eat as much as they wished at other meals or snacks. For final weeks four and five, the conditions were reversed for the two groups. Consuming the portion controlled lunches resulted in about a 250 kcal reduction in energy intake. More importantly, no sign of caloric compensation was evident across the 10 days of testing, an observation substantiated by a significant loss of body weight. The results suggest that the mere substitution of one smaller portioned meal each day is sufficient to cause reduction in daily energy intake and a significant amount of weight.

Perinatal choline supplementation improves cognitive functioning and emotion regulation in the Ts65Dn mouse model of Down syndrome

In addition to mental retardation, individuals with Down syndrome (DS) also develop the neuropathological changes typical of Alzheimer's disease (AD) and the majority of these individuals exhibit dementia. The Ts65Dn mouse model of DS exhibits key features of these disorders, including early degeneration of cholinergic basal forebrain (CBF) neurons and impairments in functions dependent on the two CBF projection systems; namely, attention and explicit memory. Herein, we demonstrate that supplementing the maternal diet with excess choline during pregnancy and lactation dramatically improved attentional function of the adult trisomic offspring. Specifically, the adult offspring of choline-supplemented Ts65Dn dams performed significantly better than unsupplemented Ts65Dn mice on a series of 5 visual attention tasks, and in fact, on some tasks did not differ from the normosomic (2N) controls. A second area of dysfunction in the trisomic animals, heightened reactivity to committing an error, was partially normalized by the early choline supplementation. The 2N littermates also benefited from increased maternal choline intake on 1 attention task. These findings collectively suggest that perinatal choline supplementation might significantly lessen cognitive dysfunction in DS and reduce cognitive decline in related neurodegenerative disorders such as AD.

A mouse model of fragile X syndrome exhibits heightened arousal and/or emotion following errors or reversal of contingencies

This study was designed to further assess cognitive and affective functioning in a mouse model of Fragile X syndrome (FXS), the Fmr1(tm1Cgr) or Fmr1 "knockout" (KO) mouse. Male KO mice and wild-type littermate controls were tested on learning set and reversal learning tasks. The KO mice were not impaired in associative learning, transfer of learning, or reversal learning, based on measures of learning rate. Analyses of videotapes of the reversal learning task revealed that both groups of mice exhibited higher levels of activity and wall-climbing during the initial sessions of the task than during the final sessions, a pattern also seen for trials following an error relative to those following a correct response. Notably, the increase in both behavioral measures seen early in the task was significantly more pronounced for the KO mice than for controls, as was the error-induced increase in activity level. This pattern of effects suggests that the KO mice reacted more strongly than controls to the reversal of contingencies and pronounced drop in reinforcement rate, and to errors in general. This pattern of effects is consistent with the heightened emotional reactivity frequently described for humans with FXS.

Succimer chelation normalizes reactivity to reward omission and errors in lead-exposed rats

This study evaluated the efficacy of a 3-week course of succimer treatment to alleviate behavioral deficits in rats exposed to lead (Pb) for the first 4 weeks of life. A 3 x 2 factorial design was used: three levels of lead exposure (No Pb, Moderate, and High Pb) and two levels of chelation (succimer or vehicle). Behavioral testing was conducted following chelation therapy, from 2 to 9 months of age; this report presents the results of two of the administered tasks: (1) a conditional olfactory discrimination task (baseline task), and (2) a conditional olfactory discrimination task with periodic reward omission on some correct trials (RO task). In the RO task, the performance disruption produced by committing an error on the previous trial was significantly greater for both unchelated lead-exposed groups than for controls. The High Pb rats were also more sensitive to reward omission than controls, providing converging evidence for impaired regulation of arousal or emotion. Importantly, succimer treatment was effective in normalizing the heightened reactivity of the lead-exposed animals to both errors and reward omission. In addition, non-lead-exposed rats that were treated with succimer tended to be more affected by a prior error than controls in their latency to respond on post-error trials. In sum, these findings provide new evidence that succimer chelation can significantly lessen the lasting neurobehavioral dysfunction produced by early lead exposure, but also suggest that there may be risks of administering the drug to individuals without elevated blood lead levels.

Succimer chelation improves learning, attention, and arousal regulation in lead-exposed rats but produces lasting cognitive impairment in the absence of lead exposure

BACKGROUND

There is growing pressure for clinicians to prescribe chelation therapy at only slightly elevated blood lead levels. However, very few studies have evaluated whether chelation improves cognitive outcomes in Pb-exposed children, or whether these agents have adverse effects that may affect brain development in the absence of Pb exposure.

OBJECTIVES

The present study was designed to answer these questions, using a rodent model of early childhood Pb exposure and treatment with succimer, a widely used chelating agent for the treatment of Pb poisoning.

RESULTS

Pb exposure produced lasting impairments in learning, attention, inhibitory control, and arousal regulation, paralleling the areas of dysfunction seen in Pb-exposed children. Succimer treatment of the Pb-exposed rats significantly improved learning, attention, and arousal regulation, although the efficacy of the treatment varied as a function of the Pb exposure level and the specific functional deficit. In contrast, succimer treatment of rats not previously exposed to Pb produced lasting and pervasive cognitive and affective dysfunction comparable in magnitude to that produced by the higher Pb exposure regimen.

CONCLUSIONS

These are the first data, to our knowledge, to show that treatment with any chelating agent can alleviate cognitive deficits due to Pb exposure. These findings suggest that it may be possible to identify a succimer treatment protocol that improves cognitive outcomes in Pb-exposed children. However, they also suggest that succimer treatment should be strongly discouraged for children who do not have elevated tissue levels of Pb or other heavy metals.

Monitoring weight daily blocks the freshman weight gain: a model for combating the epidemic of obesity

BACKGROUND

The Tissue Monitoring System (TMS) is an algorithm that estimates changes in body tissue from a series of daily weight measures. It is intended to provide people with a feedback of changes in their tissue weight so they may have a basis for estimating how much they would have to change their intake or expenditure to maintain their weight at a prescribed level. We tested the effectiveness of the TMS to prevent freshmen from gaining weight during their first semester in college.

METHODS

In two similar but independent studies (Fall 2002, 2003), female freshmen college students were given analog bathroom scales and instructed to weigh themselves each morning immediately after rising from bed, then e-mail their weight to our staff. After 7 days, a linear function was performed on the most recent 7 days of the weight-day function for each participant. In the first study, the slope of this function was e-mailed back to the participants. In the second study, the difference between last point and the original weight was determined, using linear regression techniques, converted to calories, and the information was e-mailed back to the participants. Control participants in both studies were weighed at the beginning and the end of the semester.

RESULTS

The untreated controls gained 3.1+/-0.51 kg and 2.0+/-0.65 kg, respectively (P<0.01 for both studies), whereas weight gain of the experimental groups was 0.1+/-0.99 kg and -0.82+/-0.56 kg, values that were not significantly different than zero.

CONCLUSIONS

The TMS appears to be an effective technique to help female college freshmen resist gaining weight in an environment that is conducive to weight gain. These results suggest that the TMS may be a useful method to help curb the slow increase in the prevalence of overweight and obesity that is characteristic of all industrialized societies.

Attentional dysfunction, impulsivity, and resistance to change in a mouse model of fragile X syndrome

On a series of attention tasks, male mice with a mutation targeted to the fragile X mental retardation 1 (Fmrl) gene (Fmrl knockout [KO] mice) committed a higher rate of premature responses than wild-type littermates, with the largest differences seen when task contingencies changed. This finding indicates impaired inhibitory control, particularly during times of stress or arousal. The KO mice also committed a higher rate of inaccurate responses than controls, particularly during the final third of each daily test session, indicating impaired sustained attention. In the selective attention task, the unpredictable presentation of potent olfactory distractors produced a generalized disruption in the performance of the KO mice, whereas for controls, the disruption produced by the distractors was temporally limited. Finally, the attentional disruption seen following an error was more pronounced for the KO mice than for controls, further implicating impaired regulation of arousal and/or negative affect. The present study provides the first evidence that the Fmrl KO mouse is impaired in inhibitory control, attention, and arousal regulation, hallmark areas of dysfunction in fragile X syndrome. The resistance to change also seen in these mice provides a behavioral index for studying the autistic features of this disorder.

The non-regulation of food intake in humans: Hope for reversing the epidemic of obesity

Few doubt that human feeding behavior is part of larger biology regulatory system of energy stores, but the extent to which eating behavior is controlled by these biology systems and how much is due to responses to environmental stimuli is presently under debate. The results of a series of studies are presented which have attempted to determine the responsiveness of human feeding behavior to some of the "classic" biological variables that have conventionally been used to argue the biological basis of eating behavior. When humans are challenged with either overfeeding, underfeeding, or alterations of the caloric density of the diet, they fail to demonstrate precise caloric compensation. When challenged with changes in environmental stimuli, on the other hand, humans appear to be very sensitive to changes in portion size, the number of people with whom they eat, the amount that others eat and the variety of foods available. Other more chronic influences demonstrate that body weight appears to change when people move from one area of the world to another, when they enter the college environment, or when they either marry or break up. It is argued that because humans appear to be more responsive to the external environment than internal biological cues, it should be possible to curb or even reverse the epidemic of obesity by changing aspects of the external environment or human interactions with environmental variables rather than changing their internal environment through pharmacology.

Children eat what they are served: the imprecise regulation of energy intake

Total daily food intake of 16 preschool children 4-6 years of age were collected from 5 to 7 consecutive days. The most powerful determinant of the amount of food consumed at meals was amount served (r=0.77, P<0.0001). Although intake at meals (snacks were considered a meals) was significantly negatively correlated with the amount and energy intake at the previous meal (r=-0.27, P=0.0001), the amount served was also negatively correlated with the amount served at the previous meal (P<0.02). Children did not adjust the amount consumed in response to the energy density of the meal resulting in an energy intake that was directly related to the energy density of the meals (P<0.0001). In addition, intake at meals was not depressed by energy consumed as snacks between meals. The present results indicate that eating behavior of children is similar to adults in that they display very poor regulation of energy intake and are responsive to environmental stimuli. The conclusion from this study is that both the cause of overweight in children, as well as its prevention, may lie in the hands of the caregiver.

Imprecise control of energy intake: Absence of a reduction in food intake following overfeeding in young adults

The objective was to examine the extent to which overfeeding reduces spontaneous food intake in humans. Twelve normal-weight adults participated in the three stage study. During the 14 day baseline period and 21 day recovery period, food intake was consumed ad libitum, beyond a minimum 5 MJ (1200 kcal) basal diet. During the 13 day period of overfeeding, each subject consumed 35% more energy than they consumed at baseline. Overfeeding resulted in a weight gain of 2.3+/-0.37 kg, (p<0.0001), approximately half the weight gain was determined to be fat (1.2+/-0.19 kg, p<0.0001) by underwater densitometry. Following overfeeding, mean daily caloric intake was not significantly suppressed returning immediately to baseline values. Despite normal energy intake, participants lost 1.3+/-0.24 kg of body weight (p<0.0001), of which 0.75+/-0.15 kg (p<0.0001) was fat. These results indicated that (1) the physiological control of eating behavior in humans is not the major mechanism responsible for the recovery of body weight following a period of overfeeding and (2) an increase in energy expenditure of 1.28 MJ (307 kcal)/day or about 14% was required to account for the weight loss following overfeeding.

Impaired sustained attention and error-induced stereotypy in the aged Ts65Dn mouse: a mouse model of Down syndrome and Alzheimer's disease

This study compared performance of 15- to 17-month-old Ts65Dn mice to that of littermate controls on an automated sustained attention task in which the location, onset time, and duration of brief visual cues varied unpredictably. Ts65Dn mice committed more omission errors than controls, particularly on trials with the briefest cues. Videotape data revealed that the trisomic mice attended less than controls during the period before cue presentation and engaged in stereotypic jumping and grooming immediately after making an error. These findings reveal that Ts65Dn mice are impaired in sustaining attention and exhibit heightened reactivity to committing an error, and support the validity of this mouse model for studying Down syndrome and Alzheimer's disease. The attention task, coupled with the videotape analyses of task performance, provides a useful paradigm for studying attention and reactivity to errors in mice.

The freshman weight gain: a model for the study of the epidemic of obesity

OBJECTIVE

The objective of this study was to quantify the weight gain of freshmen during their first 12 weeks at Cornell University. In addition, students completed questionnaires that revealed particular behaviors and activities that were associated with weight gain.

DESIGN

Serial, correlational study.

SUBJECTS

A total of 68 freshmen from Cornell University.

MEASUREMENT

A total of 60 students were weighed during the first week of the semester, then again 12 weeks later. They were also given a questionnaire to complete concerning their behavior during the previous 12 weeks.

RESULTS

After adjusting for clothing weights, the mean weight gain of the freshmen was 1.9+/-2.4 kg, a value significantly different from 0. Two regression models generated from the questionnaire were fitted to the weight gain. The first linear regression model (Model 1) accounted for 58% of the variance and indicated that eating in the 'all-you-can-eat' dining halls accounted for 20% of the variance in weight gain. Snacking and eating high-fat 'junk food' accounted for anther 20%. When initial weight was used as a covariate (Model 2), the consumption of junk foods, meal frequency and number of snacks accounted for 47% of the variance.

CONCLUSION

The study clearly demonstrated that significant weight gain during first semester college is a real phenomenon and can be attributed to tangible environmental stimuli. The weight gain is considerably greater than that observed in the population and may be useful as a model to test various techniques that may reduce or reverse the 'epidemic' of obesity observed in the general population.

The more food young adults are served, the more they overeat

Young and Nestle suggested that the increase in the portion size of food products evident in the United States during the past 20 years may be responsible for the epidemic of overweight and obesity. They based their conclusion on statistical correlations. The purpose of the present study was to provide experimental evidence to support their proposal. Cornell undergraduate students were given access to a buffet lunch on Monday, Wednesday, and Friday and were told this was a test of flavor enhancers. They were instructed to eat as much or as little as they wanted. On the same days of the following week, the subjects were divided into 3 groups. Each group was served either 100%, 125%, or 150% of the amount of food they had consumed the previous week. When larger amounts were served, significantly greater amounts of food were consumed. Each of the 4 foods that comprised the meal (soup, pasta, breadsticks, ice cream) increased significantly in proportion to the portion size. The data clearly support the hypothesis proposed by Young and Nestle and support the powerful role that environment plays in determining energy intake and potential increases in body weight.

Enduring effects of prenatal cocaine exposure on selective attention and reactivity to errors: evidence from an animal model

Adult Long-Evans rats, exposed prenatally to 1 of 4 doses of cocaine (0.0,0.5,1.0, or 3.0 mg/kg iv), were tested on a 3-choice visual attention task with an olfactory distractor presented unpredictably on one third of the trials. The performance of all 3 cocaine-exposed groups was significantly more disrupted than that of controls by the presentation of distractors. Results demonstrate that prenatal cocaine exposure increases susceptibility to distractors, using a task specifically designed to measure this function. In addition, the present study revealed that individuals exposed to cocaine in utero exhibit greater performance disruption after an error than controls, in certain types of tasks. Both areas of dysfunction, impaired selective attention and impaired arousal regulation, have important functional consequences in humans, possibly affecting the school performance and social development of cocaine-exposed children.

Prenatal cocaine exposure does not alter working memory in adult rats

The present study was designed to assess working memory in adult rats exposed to intravenous cocaine in utero, as part of an examination of various cognitive and affective functions. The study included four groups: a saline control and three groups exposed to ascending doses of cocaine from gestational days 8 to 21 (0.5, 1.0, or 3.0 mg/kg). This exposure regimen (route of administration and dose) has been shown to accurately reproduce the pharmacokinetic profile and physiological effects of human recreational cocaine use. This report describes the results of a series of automated alternation tasks, in which the animals were rewarded for alternating their responses between two response ports on successive trials. In the final task, the delay between trials varied randomly between 0, 20, 40, and 80 s, thereby varying the retention interval. Although performance declined dramatically as the retention interval increased, the rate of this decline did not differ across treatment groups. These results suggest that prenatal cocaine exposure, at doses that model recreational use, does not produce lasting changes in explicit memory or working memory. However, subtle, sex-specific effects of prenatal cocaine exposure were seen on measures that indicate impairments in sustained attention and "readiness", as well as altered reactivity to task-related stressors such as waiting for long and unpredictable delays.

Impaired sustained attention and altered reactivity to errors in an animal model of prenatal cocaine exposure

Although correlations have been reported between maternal cocaine use and impaired attention in exposed children, interpretation of these findings is complicated by the many risk factors that differentiate cocaine-exposed children from SES-matched controls. For this reason, the present dose-response study (0, 0.5, 1.0, or 3.0 mg/kg cocaine HCl) was designed to explore the effect of prenatal cocaine exposure on visual attention in a rodent model, using an intravenous injection protocol that closely mimics the pharmacokinetic profile and physiological effects of human recreational cocaine use. In adulthood, animals were tested on an attention task in which the duration, location, and onset time of a brief visual cue varied randomly between trials. The 3.0 mg/kg exposed males committed significantly more omission errors than control males during the final 1/3 of each testing session, specifically on trials that followed an error, which implicates impaired sustained attention and increased reactivity to committing an error. During the final 1/3 of each testing session, the 0.5 and 1.0 mg/kg exposed females took longer to enter the testing alcove at trial onset, and failed to enter the alcove more frequently than control females. Because these effects were not seen in other tasks of similar duration and reinforcement density, these findings suggest an impairment of sustained attention. This inference is supported by the finding that the increase in omission errors in the final block of trials in each daily session (relative to earlier in the session) was significantly greater for the 1.0 mg/kg females than for controls, a trend also seen for the 0.5 mg/kg group. Unlike the cocaine-exposed males, who remain engaged in the task when attention is waning, the cocaine-exposed females appear to opt for another strategy; namely, refusing to participate when their ability to sustain attention is surpassed.

Nutritional and energetic consequences of sweetened drink consumption in 6- to 13-year-old children

OBJECTIVE

To study the effects of excessive sweetened drink consumption on daily energy balance and nutrient intake in a longitudinal study of children.

SUBJECTS AND METHODS

Daily dietary intakes of 30 children aged 6 to 13 years old were collected over 4 to 8 weeks. Weights and heights of children were measured at the beginning and end of the study in 21 children. Data were analyzed by analysis of variance (ANOVA) (PROC MIXED in SAS) and multiple regression.

RESULTS

Excessive sweetened drink consumption (>12 oz/day) displaced milk from children's diets (122-147 g/day less milk drank, P <.0001) because caregivers served less milk and the children consumed smaller amounts of milk. The consequences were lower daily protein, calcium, magnesium, phosphorus, and vitamin A intakes. Because children failed to reduce consumption of solid foods to compensate for the caloric contribution of sweetened drinks, higher daily energy intakes were observed. Consequently, the greater the sweetened drink consumption the greater the weight gain (1.12 +/- 0.7 kg) compared with children who consumed <12 oz per day (0.32-0.48 +/- 0.4 kg).

CONCLUSIONS

Excessive sweetened drink consumption is associated with the displacement of milk from children's diets, higher daily energy intake, and greater weight gain.

Enduring effects of prenatal cocaine exposure on attention and reaction to errors

Rats exposed to cocaine prenatally were administered a series of 3-choice visual attention tasks, with the most pronounced deficits seen in a task in which the onset time, location, and duration of a visual cue varied unpredictably between trials. The cocaine-exposed rats were less accurate than controls but did not differ in the rate of premature responses or omission errors. The pattern of errors, coupled with response latency data, implicated deficits in the ability to rapidly engage attention and maintain a high level of alertness to the task. The cocaine-exposed rats also exhibited a blunted reaction to an error on the previous trial, possibly reflecting an alteration in emotional regulation and/or error monitoring. Implications for underlying neuropathology are discussed.

Enduring effects of prenatal cocaine exposure on attention and reaction to errors

Rats exposed to cocaine prenatally were administered a series of 3-choice visual attention tasks, with the most pronounced deficits seen in a task in which the onset time, location, and duration of a visual cue varied unpredictably between trials. The cocaine-exposed rats were less accurate than controls but did not differ in the rate of premature responses or omission errors. The pattern of errors, coupled with response latency data, implicated deficits in the ability to rapidly engage attention and maintain a high level of alertness to the task. The cocaine-exposed rats also exhibited a blunted reaction to an error on the previous trial, possibly reflecting an alteration in emotional regulation and/or error monitoring. Implications for underlying neuropathology are discussed.

Putting behavior back into feeding behavior: a tribute to George Collier

In an attempt to explain my failure to find any correlation between meal size and intermeal intervals in free-feeding rats, George Collier, my mentor, suggested that perhaps eating behavior had strong extra-physiological determinants, a heretical idea that had an enormous impact on my subsequent research. After moving to Cornell University, my students and I began a series of studies, first with animals, then with humans, all of which supported George's idea. We observed that, under our test conditions, humans (a) do not respond to overfeeding by reducing their food intake, (b) do not change the amount they consume at meals when snacks or breakfasts are added or subtracted from their daily intake, (c) do not change the amount they eat when the energy density of their food is changed, (d) nor do they increase their intake following a semi or total fast for 24 h. They also increase the amount they consume proportionally to the amount of food they are served, the variety of foods offered, and the number of people with whom they eat. The combination of these data with George's insightful idea, has merged into a modification of the popular Set-Point Theory of the regulation of body weight. The alternative "Settling Zone" Theory suggests that whereas biology may determine a range of body weights (adiposity) that are maintained fairly constant for long periods of time, within this "zone", the behaviors responsible for controlling energy intake and energy expenditure are influenced primarily by environmental and cognitive stimuli. The size of the "Settling Zone" is not currently known, but if it is 10% or greater, then efforts to identify and understand the environmental and cognitive stimuli that influence body weight may produce advances that will reduce our high rates of overweight and obesity.

The effect of microgravity and space flight on the chemical senses

The effect of space flight and microgravity on the chemical senses is reviewed. Skylab-4 and Soyuz 30-31 studies revealed changes in taste thresholds while no effect was found in a Canadian investigation (41-G) and conflicting results were obtained on another Soyuz mission. Two simulated microgravity studies found no effect on taste or smell sensitivity; while 5 other studies found an effect. Microgravity induces physiological changes including an upward shift of body fluids toward the head, which may lead to an attenuation of the olfactory component in the flavor of foods. Chemosensory changes may also relate to space sickness, Shuttle atmosphere, stress, radiation, and psychological factors.

Early lead exposure produces lasting changes in sustained attention, response initiation, and reactivity to errors

The present study tested the hypothesis that early lead (Pb) exposure causes lasting attentional dysfunction. Long-Evans dams were fed Pb-adulterated water during gestation and/or lactation; the offspring were tested as adults. The results of a visual discrimination task revealed no Pb effects on learning rate or information-processing speed. However, lasting effects of the early Pb exposure were seen in the subsequent vigilance tasks, particularly in the final task in which onset of the visual cue and cue duration varied randomly across trials. Exposure during both gestation and lactation impaired response initiation. In addition, animals exposed to Pb during lactation only or lactation+gestation committed significantly more omission errors than controls under two specific conditions: (1) trials in which a delay was imposed prior to cue presentation and (2) trials that followed an incorrect response. The pattern of treatment differences indicated that early Pb exposure produced lasting impairment of sustained attention and increased reactivity to errors. Both effects may contribute to the cognitive impairment, problematic classroom behaviors, and increased delinquency associated with early Pb exposure in children. These findings also demonstrate that the developmental timing of the exposure determines the pattern of effects. Thus, conclusions regarding whether or not a particular cognitive or affective function is impaired or spared by early Pb exposure must be limited to the specific timing and intensity of exposure.

Recovery of associative function following early amygdala lesions in rats

Adult rats with amygdala lesions made at either Postnatal Day (PND) 10 or PND40 were tested on a series of reversal tasks that tap the ability to form stimulus-reward associations. PND40 rats were significantly impaired relative to both controls and PND10 rats on learning rate of the original discrimination and subsequent reversals. Analyses of discrete learning phases revealed that the impairment was specific to the postchance phase. The PND10 group was not impaired relative to controls on any measure. These results confirm prior findings that amygdala lesions sustained in adulthood impair the formation of stimulus-reward associations. They also demonstrate that substantial sparing or recovery of function is possible when the lesion is made during early development. Furthermore, the findings support the view that behavioral recovery may be more likely if the lesion is sustained near the time of peak synaptogenesis.

Prenatal cocaine exposure impairs selective attention: evidence from serial reversal and extradimensional shift tasks

This study assessed the effects of prenatal cocaine exposure on cognitive functioning, using an intravenous (IV) rodent model that closely mimics the pharmacokinetics seen in humans after smoking or IV injection and that avoids maternal stress and undernutrition. Cocaine-exposed males were significantly impaired on a 3-choice, but not 2-choice, olfactory serial reversal learning task. Both male and female cocaine-exposed rats were significantly impaired on extradimensional shift tasks that required shifting from olfactory to spatial cues; however, they showed no impairment when required to shift from spatial to olfactory cues. In-depth analyses of discrete learning phases implicated deficient selective attention as the basis of impairment in both tasks. These data provide clear evidence that prenatal cocaine exposure produces long-lasting cognitive dysfunction, but they also underscore the specificity of the impairment.

Effects of chronic lead exposure on learning and reaction time in a visual discrimination task

Long-Evans rats exposed chronically to lead (Pb) acetate (0, 75, or 300 ppm) were tested as adults on an automated, three-choice visual discrimination task as part of a larger study designed to elucidate the cognitive effects of developmental Pb exposure. Median adult BPb levels for the groups were <5, 20, and 36 microgram/dl. The pattern of results suggested a linear effect, with increasing lead dose producing progressively slower learning and an increased incidence of "impaired" individuals. This latter measure proved to be slightly more sensitive than the former, suggesting individual differences in susceptibility to Pb neurotoxicity. Additional analyses revealed that the impairing effect of Pb was seen in both the chance and post-chance learning phases, indicating that the deficit was not limited to (but could include) attentional function. Reaction time on incorrect trials was reduced in the 300-ppm group, whereas no Pb effect was seen for correct trials. The present findings suggest that chronic developmental Pb exposure produces an associative deficit as well as a tendency to respond rapidly, but does not affect information-processing speed.

Enduring effects of early lead exposure: evidence for a specific deficit in associative ability

Long-Evans dams were exposed to Pb acetate in the drinking water during both gestation and lactation, or lactation only. This report presents the results of an automated, olfactory, serial reversal task administered to the adult offspring. Although overall learning rate was not significantly affected by Pb exposure, analyses of specific phases of the learning process revealed that all three exposed groups required significantly more trials than controls to reach criterion from the point at which perseverative responding to the previously correct cue ended. These in-depth analyses revealed that the reversal learning impairment of the Pb-exposed animals was not due to a deficit in inhibiting responses to the previously correct cue, the mechanism commonly assumed to underlie impaired reversal learning. Instead, the analyses revealed that two other independent Pb effects were responsible for the prolonged postperseverative learning period: a response bias and an impaired ability to associate cues and/or actions with affective consequences. The contribution of these two factors varied as a function of the timing and intensity of the Pb exposure. It is hypothesized that the Pb-induced associative deficit may reflect lasting damage to the amygdala and/or nucleus accumbens, which comprise a system thought to modulate the process by which environmental cues acquire affective significance.

The promotion effect of anorectic drugs on aflatoxin B(1)-induced hepatic preneoplastic foci

The ability of three extensively used anorectic drugs, namely fenfluramine (FN), fluoxetine (FX) and amphetamine (AM), to alter the development of aflatoxin B(1) (AFB(1))-induced gamma-glutamyl-positive (GGT(+)) preneoplastic liver foci was investigated in 135 male weanling F344 rats. Following AFB(1) administration, 15 rats were killed, while the rest were divided into four groups and fed diets containing either FN, FX, AM or control diet, with half of the animals in each group subsequently being killed at 4 weeks and half at 10 weeks. All three anorectic drugs as expected suppressed initial food intake, growth rate, body weight gain and food efficiency. They also tended to suppress body fat mass and to decrease plasma levels of T(3) and T(4). FN significantly (P < 0.05) increased GGT(+) foci number/cm(2) and number/cm(3), while FX significantly increased GGT(+) foci number/cm(2) and the volume fraction of foci. Histopathological staining also revealed that FN- and FX-treated animals had more serious morphological alterations in their liver tissue. In contrast, foci development was, if anything, suppressed by AM feeding. These results indicate that serotoninergic drugs (FN and FX), as opposed to dopaminergic drugs (AM), may have tumor promoter activity, at least for liver tissue.

Effects of dietary mixtures of amino acids on fetal growth and maternal and fetal amino acid pools in experimental maternal phenylketonuria

BACKGROUND

Branched-chain amino acids have been reported to improve fetal brain development in a rat model in which maternal phenylketonuria (PKU) is induced by the inclusion of an inhibitor of phenylalanine hydroxylase, DL-p-chlorophenylalanine, and L-phenylalanine in the diet.

OBJECTIVE

We studied whether a dietary mixture of several large neutral amino acids (LNAAs) would improve fetal brain growth and normalize the fetal brain amino acid profile in a rat model of maternal PKU induced by DL-alpha-methylphenylalanine (AMPhe).

DESIGN

Long-Evans rats were fed a basal diet or a similar diet containing 0.5% AMPhe + 3.0% L-phenylalanine (AMPhe + Phe diet) from day 11 until day 20 of gestation in experiments to test various mixtures of LNAAs. Maternal weight gains and food intakes to day 20, fetal body and brain weights at day 20, and fetal brain and fetal and maternal plasma amino acid concentrations at day 20 were measured.

RESULTS

Concentrations of phenylalanine and tyrosine in fetal brain and in maternal and fetal plasma were higher and fetal brain weights were lower in rats fed the AMPhe + Phe diet than in rats fed the basal diet. However, fetal brain growth was higher and concentrations of phenylalanine and tyrosine in fetal brain and in maternal and fetal plasma were lower in rats fed the AMPhe + Phe diet plus LNAAs than in rats fed the diet containing AMPhe + Phe alone.

CONCLUSION

LNAA supplementation of the diet improved fetal amino acid profiles and alleviated most, but not all, of the depression in fetal brain growth observed in this model of maternal PKU.