An explanation for the accuracy of sensor-based measures of energy intake: Amount of food consumed matters more than dietary composition.

Understanding and intervening on eating behavior often necessitates measurement of energy intake (EI); however, commonly utilized and widely accepted methods vary in accuracy and place significant burden on users (e.g., food diaries), or are costly to implement (e.g., doubly labeled water). Thus, researchers have sought to leverage inexpensive and low-burden technologies such as wearable sensors for EI estimation. Paradoxically, one such methodology that estimates EI via smartwatch-based bite counting has demonstrated high accuracy in laboratory and free-living studies, despite only measuring the amount, not the composition, of food consumed. This secondary analysis sought to further explore this phenomenon by evaluating the degree to which EI can be explained by a sensor-based estimate of the amount consumed versus the energy density (ED) of the food consumed. Data were collected from 82 adults in free-living conditions (51.2% female, 31.7% racial and/or ethnic minority; Mage = 33.5, SD = 14.7) who wore a bite counter device on their wrist and used smartphone app to implement the Remote Food Photography Method (RFPM) to assess EI and ED for two weeks. Bite-based estimates of EI were generated via a previously validated algorithm. At a per-meal level, linear mixed effect models indicated that bite-based EI estimates accounted for 23.4% of the variance in RFPM-measured EI, while ED and presence of a beverage accounted for only 0.2% and 0.1% of the variance, respectively. For full days of intake, bite-based EI estimates and ED accounted for 41.5% and 0.2% of the variance, respectively. These results help to explain the viability of sensor-based EI estimation even in the absence of information about dietary composition.

A virtual experimenter to increase standardization for the investigation of placebo effects.

BACKGROUND: Placebo effects are mediated by expectancy, which is highly influenced by psychosocial factors of a treatment context. These factors are difficult to standardize. Furthermore, dedicated placebo research often necessitates single-blind deceptive designs where biases are easily introduced. We propose a study protocol employing a virtual experimenter - a computer program designed to deliver treatment and instructions - for the purpose of standardization and reduction of biases when investigating placebo effects. METHODS: To evaluate the virtual experimenter's efficacy in inducing placebo effects via expectancy manipulation, we suggest a partially blinded, deceptive design with a baseline/retest pain protocol (hand immersions in hot water bath). Between immersions, participants will receive an (actually inert) medication. Instructions pertaining to the medication will be delivered by one of three metaphors: The virtual experimenter, a human experimenter, and an audio/text presentation (predictor "Metaphor"). The second predictor includes falsely informing participants that the medication is an effective pain killer, or correctly informing them that it is, in fact, inert (predictor "Instruction"). Analysis will be performed with hierarchical linear modelling, with a sample size of N = 50. Results from two pilot studies are presented that indicate the viability of the pain protocol (N = 33), and of the virtual experimenter software and placebo manipulation (N = 48). DISCUSSION: It will be challenging to establish full comparability between all metaphors used for instruction delivery, and to account for participant differences in acceptance of their virtual interaction partner. Once established, the presence of placebo effects would suggest that the virtual experimenter exhibits sufficient cues to be perceived as a social agent. He could consequently provide a convenient platform to investigate effects of experimenter behavior, or other experimenter characteristics, e.g., sex, age, race/ethnicity or professional status. More general applications are possible, for example in psychological research such as bias research, or virtual reality research. Potential applications also exist for standardizing clinical research by documenting and communicating instructions used in clinical trials.

Prediction of Symptom Change in Placebo Versus No-Treatment Group in Experimentally Induced Motion Sickness.

The long-standing question of who responds to placebo and who does not is of great theoretical and clinical relevance and has received increasing attention in recent years. We therefore performed a post hoc analysis of one of our previously published studies on placebo responses (PRs). In the analysis, fourteen potential predictors for the PR on experimentally induced motion sickness in 32 healthy volunteers were explored using moderated multiple regression. Generalized self-efficacy, generalized self, internal locus of control and cognitive flexibility were significantly associated with symptom improvement in the placebo group, as compared to the untreated control group. Notably, the directions of the associations were such that the "unfavorable" side of the constructs (e.g. low self-efficacy) predicted a higher PR. Instead, the "favorable" side predicted symptom improvement in the control group. Results fit well with prior research into psychological influences on motion sickness. Although PRs in motion sickness are not well established, it is suggested to include the identified constructs in future research involving motion sickness-related symptoms such as nausea and vertigo. Concerning PRs in general, the results may have implications for clinical as well as experimental research on other symptoms and disorders, such as pain or depression.

Reduction of motion sickness with an enhanced placebo instruction: an experimental study with healthy participants.

OBJECTIVE: Expectancy and conditioning are underlying mechanisms of placebo and nocebo responses. In previous studies with motion sickness, we could induce nocebo responses by both methods, but no placebo responses. METHODS: In Experiment 1, 64 volunteers (50% women, mean age = 23.5 years) were evaluated to determine the degree they realized speed changes in nauseogenic rotation. For Experiment 2, 32 volunteers (50% women, mean age = 26.0 years) were exposed to fast rotation (15 rounds per minute, or rpm) on Day 1. On Day 2, they either received a drink with a presumed effective antiemetic (actually placebo) or were told they belonged to the control group. Rotation was surreptitiously reduced (to 10 rpm). On Day 3, they were tested with the initial rotation speed. Outcome variables in both experiments were symptom ratings; additionally in Experiment 2, the number of nauseogenic head movements, tolerated rotation time, and electrogastrogram were analyzed for changes between Days 1 and 2 (expectancy plus speed reduction) and Days 1 and 3 (expectancy plus conditioning). RESULTS: In Experiment 1, a dose-response function was established for different rotation speeds, with the smallest perceived difference between 10 and 15 rpm. In Experiment 2, placebo application induced better maximal symptom rating, head movement, and rotation time at Day 2 (F = 3.097, p = .043) and Day 3 (F = 3.401, p = .031). Electrogastrogram was unaffected. CONCLUSIONS: Verbal suggestions combined with a conditioning procedure are effective in reducing symptoms of motion sickness.

Head movements and simulator sickness generated by a virtual environment.

BACKGROUND: For virtual environments (VEs) to be useful in training it is important to understand the negative effects of VE exposure. The purpose of this study was to observe head movements in virtual and real environments and the relation between those movements and simulator sickness. METHOD: There were 48 men who were trained in 4-person teams in either a head-mounted display (HMD)-based VE or in a real world environment. Head position data were collected in both systems and simulator sickness scores were collected in the VE. The relationship of head movements and sickness scores in theVE was examined and the degree of head movements in the real world and VE compared. RESULTS: Differences were found in the length of time subjects spent moving their heads; subjects with the highest sickness scores moved their heads less often than other subjects in the VE. Also, subjects moved their heads significantly less and less often in the VE (means: 3 degrees x 50 ms(-1), 71% of trial time not moving head), compared to the real world (means: 10 degrees 50 ms(-1), 59% of trial time not moving head). CONCLUSIONS: This study observed that when head movements are quantified, past assumptions of the link between increased sickness scores and decreased head movements may not hold. Though not linked to simulator sickness, head movements were reduced in the VE compared to the real world. Though observational in nature, this study is one of the first to quantify head movements and how they may relate to simulator sickness.

A virtual experimenter does not increase placebo hypoalgesia when delivering an interactive expectancy manipulation.

Lack of standardization and unblinding threaten the research of mechanisms involved in expectancy effects on pain. We evaluated a computer-controlled virtual experimenter (VEx) to avoid these issues. Fifty-four subjects underwent a baseline-retest heat pain protocol. Between sessions, they received an expectancy manipulation (placebo or no-treatment) delivered by VEx or text-only control condition. The VEx provided standardized "social" interaction with the subjects. Pain ratings and psychological state/trait measures were recorded. We found an interaction of expectancy and delivery on pain improvement following the intervention. In the text conditions, placebo was followed by lower pain, whereas in the VEx conditions, placebo and no-treatment were followed by a comparable pain decrease. Secondary analyses indicated that this interaction was mirrored by decreases of negative mood and anxiety. Furthermore, changes in continuous pain were moderated by expectation of pain relief. However, retrospective pain ratings show an effect of expectancy but not of delivery. We conclude that we successfully applied an automated protocol for inducing expectancy effects on pain. The effect of the VEx regardless of treatment may be due to interactions of attention allocation and locus of control. This points to the diversity of expectancy mechanisms, and has implications for research and computer-based treatment applications.

The role of self-efficacy and information processing in weight loss during an mHealth behavioral intervention.

Self-efficacy (SE) and information processing (IP) may be important constructs to target when designing mHealth interventions for weight loss. The goal of this study was to examine the relationship between SE and IP with weight loss at six-months as part of the Dietary Interventions Examining Tracking with mobile study, a six-month randomized trial with content delivered remotely via twice-weekly podcasts. Participants were randomized to self-monitor their diet with either a mobile app (n = 42) or wearable Bite Counter device (n = 39). SE was assessed using the Weight Efficacy Life-Style Questionnaire and the IP variables assessed included user control, cognitive load, novelty, elaboration. Regression analysis examined the relationship between weight loss, SE change & IP at six months. Results indicate that elaboration was the strongest predictor of weight loss (ß =-0.423, P = 0.011) among all SE & IP variables and that for every point increase in elaboration, participants lost 0.34 kg body weight.

Between- and Within-Subjects Predictors of the Kilocalorie Content of Bites of Food.

BACKGROUND: This study builds on previous research that seeks to estimate kilocalorie intake through microstructural analysis of eating behaviors. As opposed to previous methods, which used a static, individual-based measure of kilocalories per bite, the new method incorporates time- and food-varying predictors. A measure of kilocalories per bite (KPB) was estimated using between- and within-subjects variables. OBJECTIVE: The purpose of this study was to examine the relationship between within-subjects and between-subjects predictors and KPB, and to develop a model of KPB that improves over previous models of KPB. Within-subjects predictors included time since last bite, food item enjoyment, premeal satiety, and time in meal. Between-subjects predictors included body mass index, mouth volume, and sex. PARTICIPANTS/SETTING: Seventy-two participants (39 female) consumed two random meals out of five possible meal options with known weights and energy densities. There were 4,051 usable bites measured. MAIN OUTCOME MEASURES: The outcome measure of the first analysis was KPB. The outcome measure of the second analysis was meal-level kilocalorie intake, with true intake compared to three estimation methods. STATISTICAL ANALYSES PERFORMED: Multilevel modeling was used to analyze the influence of the seven predictors of KPB. The accuracy of the model was compared to previous methods of estimating KPB using a repeated-measured analysis of variance. RESULTS: All hypothesized relationships were significant, with slopes in the expected direction, except for body mass index and time in meal. In addition, the new model (with nonsignificant predictors removed) improved over earlier models of KPB. CONCLUSIONS: This model offers a new direction for methods of inexpensive, accurate, and objective estimates of kilocalorie intake from bite-based measures.

Internet-based assessment of bowel symptoms and quality of life.

(Table is included in full-text article). Internet-based questionnaires will, no doubt, continue to gain popularity. Internet presents an attractive medium for the researcher to collect large amounts of data with relatively little effort. The questionnaires can be available to respondents all over the world, 24 h a day, with very little labor involved. The questionnaires can be electronically scored immediately upon completion. Results can then be stored in an analyzable form or be used instantly to redirect the respondent to follow-up questionnaires. Nonetheless, good questionnaire design and psychometric principles still apply. This is true even when porting a valid paper and pencil test to the Internet. In addition, technical and logistical issues in web-based testing can affect the reliability and validity of the questionnaires. Researchers are cautioned to follow good questionnaire development practices and consider the unique problems of Internet-based instruments.

Nausea induced by vection drum: contributions of body position, visual pattern, and gender.

INTRODUCTION: The purpose of this work was to investigate intrinsic (gender) and extrinsic factors (body position, visual pattern) and their relative contribution to the development of motion sickness during pseudo-rotation. METHODS: A series of 3 experiments with 24, 12, and 48 subjects respectively, balanced for gender, was completed: Experiment 1 investigated the effect of body position (upright, supine) and gender; Experiment 2 investigated the additional influence of the visual pattern (dots, stripes), but only for the supine position; and Experiment 3 investigated the complex interaction of gender, body position, and visual pattern on symptom rating (SR), rotation tolerance (RT), and time to first perception of vection (VT). A novel vection drum that allowed varied body positions and visual patterns was used to create pseudo-rotation. RESULTS: Experiment 1: there was a significant effect of rotation on SR, and a significant rotation x position interaction such that the rotation-induced symptom increase was significantly higher in the supine compared to the upright position. In addition, there was a significant effect of gender, with women showing lower SR in both positions. RT was lower while supine compared to upright; this effect was significantly more pronounced in male subjects. Experiment 2: a significant effect of rotation on SR was found, but no effect of the visual stimulus pattern or gender on SR, RT, or VT. Women exhibited significantly lower VT than men. Experiment 3: rotation induced a significant increase in SR independent of gender, body position, and visual pattern. Supine position induced significantly higher SR and RT than upright, and a significant interaction between gender, body position, and visual pattern. CONCLUSION: The complex interaction of intrinsic and extrinsic factors may partially explain the mixed findings in the literature regarding the relationship of gender to motion sickness.

High dose ondansetron for reducing motion sickness in highly susceptible subjects.

BACKGROUND: Ondansetron is currently being explored as a treatment for motion sickness due to its proven prophylactic effect on post-operative nausea, the nausea and vomiting associated with chemotherapy, and its lack of side effects. This study sought to compare the effectiveness of placebo, dimenhydrinate, and ondansetron for preventing motion sickness in highly susceptible subjects. METHODS: A total of 63 subjects with a history of frequent motion sickness and positive report of self-treatment of motion sickness with over-the-counter medications were divided into 3 groups of 20 (3 were disqualified). Depending on their group assignment, subjects were given placebo, dimenhydrinate, or ondansetron 1 h before being rotated at 20 rpm while making head movements. Symptoms of motion sickness and electrogastrogram (EGG) data were collected prior to and during rotation. RESULTS: There were no differences between the groups in number of head movements tolerated, time rotating, or symptom questionnaire scores. All groups showed a marginally significant decrease in normal 3 cycle per minute activity [F (1.45) = 3.04, p = 0.088] and a significant increase in gastric tachyarrhythmia [F (1,45) = 9.71, p = 0.003], a pattern typically associated with motion sickness development. CONCLUSION: Neither ondansetron or dimenhydrinate prevented motion sickness in groups of highly susceptible people. Continued development of new treatments is necessary.

Human performance under sustained operations and acute sleep deprivation conditions: toward a model of controlled attention.

INTRODUCTION: Although a number of studies have examined the effects of sleep deprivation on performance, the results are not easily explained. The purpose of the current study was to examine the effects of sustained operations and acute sleep deprivation on tasks that require a wide range of information processing. The current study also provided preliminary data on the use of the controlled attention model to better understand the effects of sleep deprivation. METHODS: There were 24 college students who were paid to remain awake for one night and complete a variety of cognitive and vigilance tasks. Each task was administered four times during the night, once in each testing session (17:30-21:30, 21:45-01:45, 02:30-06:30, and 06:45-10:45). All tasks were counterbalanced across the testing sessions. RESULTS: The data were converted to z-scores and repeated-measures ANOVAs were completed. Performance did not significantly decrease on the more complex cognitive tasks over the night of sleep deprivation. Performance on the vigilance tasks decreased significantly across the night. CONCLUSIONS: Examining the characteristics of the cognitive tasks indicated that although they required different types of processing, they encouraged the participants to remain attentive to and engaged in the task. In contrast, the vigilance tasks were less intrinsically interesting and engaging. Thus, it seems likely that the participants were less capable of maintaining attention on the vigilance tasks than the cognitive tasks. These results indicate that a controlled attention model may be useful in better understanding the effects of sustained operations and sleep deprivation on performance.

Measuring the Consumption of Individual Solid and Liquid Bites Using a Table-Embedded Scale During Unrestricted Eating.

The universal eating monitor (UEM) is a table-embedded scale used to measure grams consumed over time while a person eats. It has been used in laboratory settings to test the effects of anorectic drugs and behavior manipulations such as slowing eating, and to study relationships between demographics and body weight. However, its use requires restricted conditions on the foods consumed and behaviors allowed during eating in order to simplify analysis of the scale data. Individual bites can only be measured when the only interaction with the scale is to carefully remove a single bite of food, consume it fully, and wait a minimum amount of time before the next bite. Other interactions are prohibited such as stirring and manipulating foods, retrieving or placing napkins or utensils on the scale, and in general anything that would change the scale weight that was not related to the consumption of an individual bite. This paper describes a new algorithm that can detect and measure the weight or individual bites consumed during unrestricted eating. The algorithm works by identifying time periods when the scale weight is stable, and then, analyzing the surrounding weight changes. The series of preceding and succeeding weight changes is compared against patterns for single food bites, food mass bites, and drink bites to determine if a scale interaction is due to a bite or some other activity. The method was tested on 271 subjects, each eating a single meal in a cafeteria setting. A total of 24 101 bites were manually annotated in synchronized videos to establish ground truth as to the true, false, and missed detections of bites. Our algorithm correctly detected and weighed approximately 39% of bites with approximately one false positive (FP) per ten actual bites. The improvement compared to the UEM is approximately three times the number of true detections and a 90% reduction in the number of FPs. Finally, an analysis of bites that could not be weighed compared to those that could be weighed revealed no statistically significant difference in average weight. These results suggest that our algorithm could be used to conduct studies using a table scale outside of laboratory or clinical settings and with unrestricted eating behaviors.

A comparison of bite size and BMI in a cafeteria setting.

Our study investigated the relationship between BMI and bite size in a cafeteria setting. Two hundred and seventy one participants consumed one meal each. Participants were free to select any food provided by the cafeteria and could return for additional food as desired. Bite weights were measured with a table embedded scale. Data were analyzed with ANOVAs, regressions, Kolmogorov-Smirnov tests, and a repeated measures general linear model for quartile analysis. Obese participants were found to take larger bites than both normal (p=0.002) and overweight participants (p=0.017). Average bite size increased by 0.20g per point increase in BMI. Food bites and drink bites were analyzed individually, showing 0.11g/BMI and 0.23g/BMI slopes, respectively. Quartiles of bites were also analyzed, and a significant interaction was found between normal and obese participants (p=0.034) such that the lower two quartiles were similar, but the upper two quartiles showed an increase in bite size for obese participants. The source of these effects could be the result of a combination of several uncontrolled factors.

Different Disclosed Probabilities to Receive an Antiemetic Equally Decrease Subjective Symptoms in an Experimental Placebo Study: To Be or Not to Be Sure.

PURPOSE: The purpose of this study was to examine whether the disclosed probability of receiving an antiemetic affects nausea. METHODS: Forty-eight healthy participants (mean [SD] age, 26.8 [5.4] years; 50% female) were exposed to 5 × 2 minutes of nauseogenic body rotations on 2 days. On day 2, participants were randomized to 3 experimental groups that were given different instructions concerning the probability of receiving an antiemetic remedy (100%, 50%, or 0% probability), whereas all received an inert substance. Subjective symptoms, behavioral (rotation tolerance) measures, and physiologic (electrogastrogram) measures of nausea were assessed and mediator and moderator analyses performed for effects of expectations and psychological characteristics on outcomes. FINDINGS: Disclosed probabilities of both 100% and 50% significantly reduced subjective symptoms of nausea in an equal manner compared with the 0% probability group from day 1 to day 2. This effect was found for neither rotation tolerance nor myoelectric gastric activity. Expectations and psychological characteristics did not affect the results found. Post hoc analyses revealed that women only seem to be susceptible to this placebo effect. IMPLICATIONS: Nausea is susceptible to placebo effects independent of the disclosed probability of receiving a drug and of explicit expectations. In line with placebo research, this effect is probably attributable to central mechanisms, and it is speculated that it could be related to the reward circuitry and social interactions.

Byte by Bite: Use of a mobile Bite Counter and weekly behavioral challenges to promote weight loss.

The goal of this study was to examine the usability and feasibility of the mobile Bite Counter (a watch-like device that detects when a user consumes food or beverage) and the impact of weekly behavioral challenges on diet and physical activity outcomes. Overweight (mean BMI 31.1±4.9 kg/m2) adults (n=12) were recruited to participate in a four-week study to test both the usability and feasibility of using the device as part of a behavioral weight loss intervention. Participants were instructed to self-monitor number of bites/day using the Bite Counter, attend weekly group sessions, and listen to weekly podcasts. Participants were given weekly challenges: use a daily bite limit goal (wk1), turn off Bite Counter when fruits/vegetables are consumed (wk2), self-monitor kilocalories vs. bites (wk3), and receive a 10 bites/day bonus for every 30 minutes of exercise (wk4). Participants lost a mean of -1.2±1.3 kg. Only the wk3 challenge produced significant differences in kcal change (wk3 1302±120 kcal/day vs. baseline 2042±302 kcal/d, P<0.05). Bite Counter use was significantly correlated with weight loss (r= -0.58, P<0.05). Future studies should examine the use of the Bite Counter and impact of behavioral challenges over a longer period of time in a controlled study.

The Dietary Intervention to Enhance Tracking with Mobile Devices (DIET Mobile) Study: A 6-Month Randomized Weight Loss Trial.

OBJECTIVE: To examine the use of two different mobile dietary self-monitoring methods for weight loss. METHODS: Adults with overweight (n = 81; mean BMI 34.7 ± 5.6 kg/m2 ) were randomized to self-monitor their diet with a mobile app (App, n = 42) or wearable Bite Counter device (Bite, n = 39). Both groups received the same behavioral weight loss information via twice-weekly podcasts. Weight, physical activity (International Physical Activity Questionnaire), and energy intake (two dietary recalls) were assessed at 0, 3, and 6 months. RESULTS: At 6 months, 75% of participants completed the trial. The App group lost significantly more weight (-6.8 ± 0.8 kg) than the Bite group (-3.0 ± 0.8 kg; group × time interaction: P < 0.001). Changes in energy intake (kcal/d) (-621 ± 157 App, -456 ± 167 Bite; P = 0.47) or number of days diet was tracked (90.7 ± 9.1 App, 68.4 ± 9.8 Bite; P = 0.09) did not differ between groups, but the Bite group had significant increases in physical activity metabolic equivalents (+2015.4 ± 684.6 min/wk; P = 0.02) compared to little change in the App group (-136.5 ± 630.6; P = 0.02). Total weight loss was significantly correlated with number of podcasts downloaded (r = -0.33, P < 0.01) and number of days diet was tracked (r = -0.33, P < 0.01). CONCLUSIONS: While frequency of diet tracking was similar between the App and Bite groups, there was greater weight loss observed in the App group.

Motion and space sickness: intestinal and autonomic correlates.

The purpose of this paper is to provide an overview of autonomic nervous system and gastrointestinal changes that occur during motion sickness. It is important to consider that motion sickness is a syndrome that can vary between individuals and within individuals and between and within motion sickness-inducing stimuli. Vomiting should be considered a discrete event of the motion sickness syndrome. Given so much variability in motion sickness symptoms, it should be expected that the physiological response to motion sickness will vary as well. This appears to be the case with the autonomic nervous system and gastrointestinal changes during motion sickness. Although much research remains to be done, it appears undeniable that the physiological expression of motion sickness is mediated by the autonomic nervous system, and when nausea is a predominant symptom, the stomach in general shuts down in a response characterized by decreased normal gastric myoelectrical activity and delayed gastric emptying.

Motion sickness history, food neophobia, and sensation seeking.

Motion sickness is believed to be caused by conflicting sensory signals, a situation that mimics the effects of ingesting certain toxins. Thus, one might suspect that individuals who have experienced a relatively high frequency of motion sickness may be particularly vigilant about avoiding anything that produces nausea, induding potentially nauseating toxins. Consequently, they may be more resistant to trying new foods, i.e., be more food neophobic, since unfamiliar foods can have unexpected adverse effects due to toxins or allergens. Likewise, many highly stimulating experiences can trigger motion sickness, so individuals who are more susceptible may be more prone to avoid such experiences, i.e., be less sensation seeking. Finally, it was expected that food neophobia would be more frequent in individuals low on sensation seeking tendencies. Self-reported motion sickness history in 308 adults (M= 18.8 yr.; SD = 1.6) was correlated with scores on the Arnett Inventory of Sensation Seeking and the Food Neophobia Scale. As predicted, greater history of motion sickness was associated with lower Sensation Seeking scores. Food Neophobia was not correlated with motion sickness history but, as expected, was negatively correlated (r = -.42) with scores on Sensation Seeking. Further research is recommended that measures actual sensitivity to motion sickness.

Comparison between Human and Bite-Based Methods of Estimating Caloric Intake.

BACKGROUND: Current methods of self-monitoring kilocalorie intake outside of laboratory/clinical settings suffer from a systematic underreporting bias. Recent efforts to make kilocalorie information available have improved these methods somewhat, but it may be possible to derive an objective and more accurate measure of kilocalorie intake from bite count. OBJECTIVE: This study sought to develop and examine the accuracy of an individualized bite-based measure of kilocalorie intake and to compare that measure to participant estimates of kilocalorie intake. It was hypothesized that kilocalorie information would improve human estimates of kilocalorie intake over those with no information, but a bite-based estimate of kilocalorie intake would still outperform human estimates. PARTICIPANTS/SETTINGS: Two-hundred eighty participants were allowed to eat ad libitum in a cafeteria setting. Their bite count and kilocalorie intake were measured. After completion of the meal, participants estimated how many kilocalories they consumed, some with the aid of a menu containing kilocalorie information and some without. Using a train and test method for predictive model development, participants were randomly divided into one of two groups: one for model development (training group) and one for model validation (test group). STATISTICAL ANALYSIS: Multiple regression was used to determine whether height, weight, age, sex, and waist-to-hip ratio could predict an individual's mean kilocalories per bite for the training sample. The model was then validated with the test group, and the model-predicted kilocalorie intake was compared with human-estimated kilocalorie intake. RESULTS: Only age and sex significantly predicted mean kilocalories per bite, but all variables were retained for the test group. The bite-based measure of kilocalorie intake outperformed human estimates with and without kilocalorie information. CONCLUSIONS: Bite count might serve as an easily measured, objective proxy for kilocalorie intake. A tool that can monitor bite count may be a powerful assistant to self-monitoring.