Perceived Weight Discrimination and Obesity

Weight discrimination is prevalent in American society. Although associated consistently with psychological and economic outcomes, less is known about whether weight discrimination is associated with longitudinal changes in obesity. The objectives of this research are (1) to test whether weight discrimination is associated with risk of becoming obese (Body Mass Index≥30; BMI) by follow-up among those not obese at baseline, and (2) to test whether weight discrimination is associated with risk of remaining obese at follow-up among those already obese at baseline. Participants were drawn from the Health and Retirement Study, a nationally representative longitudinal survey of community-dwelling US residents. A total of 6,157 participants (58.6% female) completed the discrimination measure and had weight and height available from the 2006 and 2010 assessments. Participants who experienced weight discrimination were approximately 2.5 times more likely to become obese by follow-up (OR = 2.54, 95% CI = 1.58–4.08) and participants who were obese at baseline were three times more likely to remain obese at follow up (OR = 3.20, 95% CI = 2.06–4.97) than those who had not experienced such discrimination. These effects held when controlling for demographic factors (age, sex, ethnicity, education) and when baseline BMI was included as a covariate. These effects were also specific to weight discrimination; other forms of discrimination (e.g., sex, race) were unrelated to risk of obesity at follow-up. The present research demonstrates that, in addition to poorer mental health outcomes, weight discrimination has implications for obesity. Rather than motivating individuals to lose weight, weight discrimination increases risk for obesity.     

The Interaction between Selection,Demography and Selfing and How It Affects Population Viability

Population extinction due to the accumulation of deleterious mutations has only been considered to occur at small population sizes, large sexual populations being expected to efficiently purge these mutations. However, little is known about how the mutation load generated by segregating mutations affects population size and, eventually, population extinction. We propose a simple analytical model that takes into account both the demographic and genetic evolution of populations, linking population size, density dependence, the mutation load, and self-fertilisation. Analytical predictions were found to be relatively good predictors of population size and probability of population viability when verified using an explicit individual based stochastic model. We show that initially large populations do not always reach mutation-selection balance and can go extinct due to the accumulation of segregating deleterious mutations. Population survival depends not only on the relative fitness and demographic stochasticity, but also on the interaction between the two. When deleterious mutations are recessive, self-fertilisation affects viability non-monotonically and genomic cold-spots could favour the viability of outcrossing populations.     

Comparison of the Effects of Flexion and Extension of the Thumb and Fingers on the Position and Cross-Sectional Area of the Median Nerve

Objective

To assess the separate effects of thumb and finger extension/flexion on median nerve position and cross-sectional area.

Methods

Ultrasonography was used to assess median nerve transverse position and cross-sectional area within the carpal tunnel at rest and its movement during volitional flexion of the individual digits of the hand. Both wrists of 165 normal subjects (11 men, 4 women, mean age, 28.6, range, 22 to 38) were studied.

Results

Thumb flexion resulted in transverse movement of the median nerve in radial direction (1.2±0.6 mm), whereas flexion of the fingers produced transverse movement in ulnar direction, which was most pronounced during flexion of the index and middle fingers (3.2±0.9 and 3.1±1.0 mm, respectively). Lesser but still statistically significant movements were noted with flexion of the ring finger (2.0±0.8 mm) and little finger (1.2±0.5 mm). Flexion of the thumb or individual fingers did not change median nerve cross-sectional area (8.5±1.1 mm²).

Conclusions

Volitional flexion of the thumb and individual fingers, particularly the index and middle fingers, produced significant transverse movement of the median nerve within the carpal tunnel but did not alter the cross-sectional area of the nerve. The importance of these findings on the understanding of the pathogenesis of the carpal tunnel syndrome and its treatment remains to be investigated.     

Perceived Racial Discrimination in the Workplace and Body Weight among the Unemployed

This study investigates the association between body weight and the likelihood that people perceive that they have been the victims of racial discrimination in the workplace among the unemployed. I find that unemployed obese men and women are 8.4 percentage points and 7.7 percentage points, respectively, more likely to have experienced racial discrimination before becoming unemployed than their non-obese counterparts. For unemployed men, the relationship between body weight and perceived racial discrimination does not seem to be associated with race. For unemployed women, being black and obese significantly increases the likelihood of perceiving racial discrimination.     

How Metal Substitution Affects the Enzymatic Activity of Catechol-O-Methyltransferase

Catechol-O-methyltransferase (COMT) degrades catecholamines, such as dopamine and epinephrine, by methylating them in the presence of a divalent metal cation (usually Mg(II)), and S-adenosyl-L-methionine. The enzymatic activity of COMT is known to be vitally dependent on the nature of the bound metal: replacement of Mg(II) with Ca(II) leads to a complete deactivation of COMT; Fe(II) is slightly less than potent Mg(II), and Fe(III) is again an inhibitor. Considering the fairly modest role that the metal plays in the catalyzed reaction, this dependence is puzzling, and to date remains an enigma. Using a quantum mechanical / molecular mechanical dynamics method for extensive sampling of protein structure, and first principle quantum mechanical calculations for the subsequent mechanistic study, we explicate the effect of metal substitution on the rate determining step in the catalytic cycle of COMT, the methyl transfer. In full accord with experimental data, Mg(II) bound to COMT is the most potent of the studied cations and it is closely followed by Fe(II), whereas Fe(III) is unable to promote catalysis. In the case of Ca(II), a repacking of the protein binding site is observed, leading to a significant increase in the activation barrier and higher energy of reaction. Importantly, the origin of the effect of metal substitution is different for different metals: for Fe(III) it is the electronic effect, whereas in the case of Ca(II) it is instead the effect of suboptimal protein structure.     

Lifestyle Intervention Favorably Affects Weight Loss and Maintenance Following Obesity Surgery

The present study was designed to evaluate the 3 year effects of a lifestyle intervention on weight loss and maintenance, dietary, and physical activity habits and eating behavior of patients following vertical banded gastroplasty (VBG). Thirty severely obese female volunteers were included in the study and they were randomly assigned to one of two intervention groups: usual care (UC) or lifestyle intervention (LS) group. Patients were followed for 3 years postoperatively. Outcome measures included weight loss, dietary habits, physical activity level (PAL), and eating behavior changes. Weight was significantly lower in the LS group after 12 months (84.4 ± 3.9 kg vs. 98.4 ± 4.4 kg, P < 0.05), 24 months (83.0 ± 3.3 vs. 101.9 ± 5.3 kg, P < 0.05), and 36 months following surgery (84.2 ± 3.3 vs. 102.5 ± 3.5 kg, P < 0.05). Repeated measures ANOVA revealed significant differences between the two groups overall and at specific time points for the PAL and TV viewing. With regard to eating behavior, the LS group scored significantly better in total Dutch Eating Behavior Questionnaire (DEBQ), Restraint Eating and External Eating scales at all postoperative time points. Similarly, significant differences were found between the two groups in dietary intake. These findings outline the importance of lifestyle intervention on weight loss and maintenance following bariatric surgery. The favorable effects of lifestyle intervention may be through adoption of healthier eating behaviors and increased physical activity.     

How the Motility Pattern of Bacteria Affects Their Dispersal and Chemotaxis

Most bacteria at certain stages of their life cycle are able to move actively; they can swim in a liquid or crawl on various surfaces. A typical path of the moving cell often resembles the trajectory of a random walk. However, bacteria are capable of modifying their apparently random motion in response to changing environmental conditions. As a result, bacteria can migrate towards the source of nutrients or away from harmful chemicals. Surprisingly, many bacterial species that were studied have several distinct motility patterns, which can be theoretically modeled by a unifying random walk approach. We use this approach to quantify the process of cell dispersal in a homogeneous environment and show how the bacterial drift velocity towards the source of attracting chemicals is affected by the motility pattern of the bacteria. Our results open up the possibility of accessing additional information about the intrinsic response of the cells using macroscopic observations of bacteria moving in inhomogeneous environments.     

Tablet Keyboard Configuration Affects Performance,Discomfort and Task Difficulty for Thumb Typing in a Two-Handed Grip

When holding a tablet computer with two hands, the touch keyboard configuration imposes postural constraints on the user because of the need to simultaneously hold the device and type with the thumbs. Designers have provided users with several possible keyboard configurations (device orientation, keyboard layout and location). However, potential differences in performance, usability and postures among these configurations have not been explored. We hypothesize that (1) the narrower standard keyboard layout in the portrait orientation leads to lower self-reported discomfort and less reach than the landscape orientation; (2) a split keyboard layout results in better overall outcomes compared to the standard layout; and (3) the conventional bottom keyboard location leads to the best outcomes overall compared to other locations. A repeated measures laboratory experiment of 12 tablet owners measured typing speed, discomfort, task difficulty, and thumb/wrist joint postures using an active marker system during typing tasks for different combinations of device orientation (portrait and landscape), keyboard layout (standard and split), and keyboard location (bottom, middle, top). The narrower standard keyboard with the device in the portrait orientation was associated with less discomfort (least squares mean (and S.E.) 2.9±0.6) than the landscape orientation (4.5±0.7). Additionally, the split keyboard decreased the amount of reaching required by the thumb in the landscape orientation as defined by a reduced range of motion and less MCP extension, which may have led to reduced discomfort (2.7±0.6) compared to the standard layout (4.5±0.7). However, typing speed was greater for the standard layout (127±5 char./min.) compared to the split layout (113±4 char./min.) regardless of device orientation and keyboard location. Usage guidelines and designers can incorporate these findings to optimize keyboard design parameters and form factors that promote user performance and usability for thumb interaction.     

Perceived Stress and Weight Gain in Adolescence: A Longitudinal Analysis

Although perceived stress has been hypothesized to be a risk factor for obesity, epidemiological studies relating stress to weight gain have shown mixed results. We examined prospective associations between perceived stress and changes in waist circumference and BMI in a large study of adolescents. As part of the Health and Behaviour in Teenagers Study (HABITS), height, weight, and waist circumference were measured annually in 4,065 adolescents aged from 11 to 16. Waist and BMI standard deviation scores (SDS) were used as indices of adiposity. Adolescents completed a measure of perceived stress each year, from which mean stress scores over the 5‐year period were also calculated and divided by tertile into lower, moderate, and higher stress. Associations between perceived stress at each year and adiposity 1–4 years later and also adiposity trajectories over the whole period in relation to mean stress were investigated. Analyses were adjusted for age, sex, ethnicity, socioeconomic deprivation, pubertal timing, and smoking. Perceived stress in any year was not related prospectively to increases in waist or BMI SDS 1–4 years later, nor was there any evidence that higher stress over the whole period was associated with greater gains in waist or BMI SDS. However, waist and BMI SDS were significantly higher in the moderate‐ and higher‐stress groups than the lower‐stress group across the whole 5‐year period. Persistent stress was associated with higher waist circumference and BMI in adolescence, but did not lead to differential changes over 5 years.     

Posture Affects How Robots and Infants Map Words to Objects

For infants, the first problem in learning a word is to map the word to its referent; a second problem is to remember that mapping when the word and/or referent are again encountered. Recent infant studies suggest that spatial location plays a key role in how infants solve both problems. Here we provide a new theoretical model and new empirical evidence on how the body – and its momentary posture – may be central to these processes. The present study uses a name-object mapping task in which names are either encountered in the absence of their target (experiments 1–3, 6 & 7), or when their target is present but in a location previously associated with a foil (experiments 4, 5, 8 & 9). A humanoid robot model (experiments 1–5) is used to instantiate and test the hypothesis that body-centric spatial location, and thus the bodies’ momentary posture, is used to centrally bind the multimodal features of heard names and visual objects. The robot model is shown to replicate existing infant data and then to generate novel predictions, which are tested in new infant studies (experiments 6–9). Despite spatial location being task-irrelevant in this second set of experiments, infants use body-centric spatial contingency over temporal contingency to map the name to object. Both infants and the robot remember the name-object mapping even in new spatial locations. However, the robot model shows how this memory can emerge –not from separating bodily information from the word-object mapping as proposed in previous models of the role of space in word-object mapping – but through the body’s momentary disposition in space.     

Lightening the Perceived Prosthesis Weight with Neural Embodiment Promoted by Sensory Feedback

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Directional Coordination of Thumb and Finger Forces during Precision Pinch

The human opposable thumb enables the hand to perform dexterous manipulation of objects, which requires well-coordinated digit force vectors. This study investigated the directional coordination of force vectors generated by the thumb and index finger during precision pinch. Fourteen right-handed, healthy subjects were instructed to exert pinch force on an externally stabilized apparatus with the pulps of the thumb and index finger. Subjects applied forces to follow a force-ramp profile that linearly increased from 0 to 12 N and then decreased to 0 N, at a rate of ±3 N/s. Directional relationships between the thumb and index finger force vectors were quantified using the coordination angle (CA) between the force vectors. Individual force vectors were further analyzed according to their projection angles (PAs) with respect to the pinch surface planes and the shear angles (SAs) within those planes. Results demonstrated that fingertip force directions were dependent on pinch force magnitude, especially at forces below 2 N. Hysteresis was observed in the force-CA relationship for increasing and decreasing forces and fitted with exponential models. The fitted asymptotic values were 156.0±6.6° and 150.8±9.3° for increasing and decreasing force ramps, respectively. The PA of the thumb force vector deviated further from the direction perpendicular to the pinching surface planes than that of the index finger. The SA showed that the index finger force vector deviated in the ulnar-proximal direction, whereas the thumb switched its force between the ulnar-proximal and radial-proximal directions. The findings shed light on the effects of anatomical composition, biomechanical function, and neuromuscular control in coordinating digit forces during precision pinch, and provided insight into the magnitude-dependent force directional control which potentially affects a range of dexterous manipulations.     

Associations Between Perceived Weight Discrimination and the Prevalence of Psychiatric Disorders in the General Population

Despite the increased prevalence of weight discrimination, few studies have examined the association between perceived weight discrimination and the prevalence of current psychiatric disorders in the general population. This study utilized a subsample of overweight and obese individuals (N = 22,231) from Wave 2 of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), a cross‐sectional nationally representative study of noninstitutionalized US adults. Perceived weight discrimination is associated with substantial psychiatric morbidity and comorbidity. These results remained significant after adjusting for a potential confound, perceived stress. Moreover, social support did not buffer against the adverse effects of perceived weight discrimination on mental health. Controlling for BMI did not diminish the associations, indicating that perceived weight discrimination is potentially harmful to mental health regardless of weight. These results highlight the urgent need for a multifaceted approach to address this important public health issue, including interventions to assist overweight individuals in coping with the mental health sequelae of perceived weight discrimination.     

How Aging Affects Grasping Behavior and Pull Strength in Captive Gray Mouse Lemurs (<Emphasis Type="Italic">Microcebus murinus</Emphasis>)

Prehension is essential for animal survival and fitness. It is involved in locomotion and feeding behavior and subject to physical and physiological constraints. Studies of prehension in primates have explored the importance of food properties and of the environment, but aging has rarely been studied although prehensile capacity may deteriorate with age in humans. To test the hypothesis that aging affects grasping abilities and to reveal possible behavioral adaptations to this, we quantified behavioral grasping strategies and pull strength in 10 young adult (2–3 yr old) and 10 aged (7–8 yr old) gray mouse lemurs (Microcebus murinus). We assessed grasping strategies in an experimental cage by quantifying grip types used to grasp static and mobile foods. We measured strength using a Kistler triaxial force platform. Our results show that 1) mobile and static foods affected individuals of different ages in similar ways; 2) older individuals used more mouth grasps than young ones; 3) aged individuals made twice as many attempts as young ones when grasping mobile food items but this difference was not significant; and 4) there were no differences in hand grip strength between age classes but young individuals showed a higher foot pull strength compared to old ones. These data suggest that the observed differences in behavior may be due to a decrease in foot grip strength, which in turn influences stability on narrow branches, forcing animals to use their hands to maintain stability and preventing them from using their hands for food-related tasks.     

Stability of the Association between Birth Weight and Childhood Overweight during the Development of the Obesity Epidemic

Objective: To assess whether changes in the birth weight distribution or changes in the association of birth weight with the later risk of childhood overweight have contributed to the development of the obesity epidemic. Research Methods and Procedures: A Danish population‐based cohort study of 124,615 girls and 128,346 boys (ages 6 to 13 years), born between 1936 and 1983, were studied. Birth weight and annual measurements of height and weight were obtained from school health records. Overweight was defined by BMI in relation to internationally accepted criteria. The relative risk of being overweight by birth weight was calculated separately for each age, sex, and time period. Results: The birth weight distribution remained relatively stable over time. Compared with children with a birth weight of 3.0 to 3.5 kg, the risk of overweight increased consistently with each increase in birth weight category among girls and boys and at all ages between 6 and 13 years. Furthermore, the association between birth weight and increased risk of overweight in childhood remained stable across a 48‐year period. Discussion: The increase in the prevalence of overweight could not be explained by time trends in the distribution of birth weight or by changes in the association between birth weight and the later risk of overweight over time. This implies that, unless the prenatal environment influences the later risk of overweight without increasing birth weight, the environmental influences contributing to the obesity epidemic in children of school age operate in the early postnatal period.