Low calorie dieting increases cortisol

Weight loss by calorie restriction versus bariatric surgery differentially regulates the hypothalamo-pituitary-adrenocortical axis in male rats

Behavioral modifications for the treatment of obesity, including caloric restriction, have notoriously low long-term success rates relative to bariatric weight-loss surgery. The reasons for the difference in sustained weight loss are not clear. One possibility is that caloric restriction alone activates the stress-responsive hypothalamo-pituitary-adrenocortical (HPA) axis, undermining the long-term maintenance of weight loss, and that this is abrogated after bariatric surgery. Accordingly, we compared the HPA response to weight loss in five groups of male rats: (1) high-fat diet-induced obese (DIO) rats treated with Roux-en-Y gastric bypass surgery (RYGB, n = 7), (2) DIO rats treated with vertical sleeve gastrectomy (VSG, n = 11), (3) DIO rats given sham surgery and subsequently restricted to the food intake of the VSG/RYGB groups (Pair-fed, n = 11), (4) ad libitum-fed DIO rats given sham surgery (Obese, n = 11) and (5) ad libitum chow-fed rats given sham surgery (Lean, n = 12). Compared with Lean controls, food-restricted rats exhibited elevated morning (nadir) non-stress plasma corticosterone concentration and increased hypothalamic corticotropin-releasing hormone and vasopressin mRNA expression, indicative of basal HPA activation. This was largely prevented when weight loss was achieved by bariatric surgery. DIO increased HPA activation by acute (novel environment) stress and this was diminished by bariatric surgery-, but not pair-feeding-, induced weight loss. These results indicate that the HPA axis is differentially affected by weight loss from caloric restriction versus bariatric surgery, and this may contribute to the differing long-term effectiveness of these two weight-loss approaches.

Effects of caloric restriction on nitrogen and carbon stable isotope ratios in adult rat bone

RATIONALE

Stable isotope analysis is a valuable technique for dietary estimation in ecological and archaeological research, yet many variables can potentially affect tissue stable isotope signatures. Controlled feeding studies across a range of species have consistently demonstrated impacts of caloric restriction on tissue stable isotope ratios, but most have focused on juvenile, fasting, and/or starving individuals, and most have utilized soft tissues despite the importance of bone for paleodietary analyses. The goal of this study was to determine whether temporally defined, moderate food restriction could affect stable carbon and/or nitrogen isotope ratios in adult mammalian bone - a tissue that arguably reflects long-term dietary signals.

METHODS

Adult rats fed a standard laboratory diet were restricted to 45% of ad libitum intakes for 3 or 6 months. Relevant anatomical and physiological parameters were measured to confirm that the restriction protocol resulted in significant nutritional stress and to provide independent data to facilitate interpretation of stable isotope ratios. Femoral bone δ(13)Ccollagen, δ(15)Ncollagen, and δ(13)Capatite values were determined by isotope ratio mass spectrometry.

RESULTS

Calorie-restricted animals exhibited a small, yet significant enrichment in (15)Ncollagen compared with control animals, reflecting protein-calorie stress. While the δ(13)Ccollagen values did not differ, the δ(13)Capatite values revealed less enrichment in (13)C than in controls, reflecting catabolism of body fat. Independent anatomical and physiological data from these same individuals support these interpretations.

CONCLUSIONS

Results indicate that moderate caloric restriction does not appreciably undermine broad interpretations of dietary signals in adult mammalian bone. Significant variability among individuals or groups, however, is best explained by marked differences in energy intake over variable timescales. An inverse relationship between the δ(13)Capatite and δ(15)Ncollagen values observed in this study indicates that a more robust pattern is expected with more severe or prolonged restriction and suggests this pattern may have utility as a marker of food deprivation in archaeological populations.

Does the method of weight loss effect long-term changes in weight, body composition or chronic disease risk factors in overweight or obese adults? A systematic review

BACKGROUND

Differences in biological changes from weight loss by energy restriction and/or exercise may be associated with differences in long-term weight loss/regain.

OBJECTIVE

To assess the effect of weight loss method on long-term changes in weight, body composition and chronic disease risk factors.

DATA SOURCES

PubMed and Embase were searched (January 1990-October 2013) for studies with data on the effect of energy restriction, exercise (aerobic and resistance) on long-term weight loss. Twenty articles were included in this review.

STUDY ELIGIBILITY CRITERIA

Primary source, peer reviewed randomized trials published in English with an active weight loss period of >6 months, or active weight loss with a follow-up period of any duration, conducted in overweight or obese adults were included.

STUDY APPRAISAL AND SYNTHESIS METHODS

Considerable heterogeneity across trials existed for important study parameters, therefore a meta-analysis was considered inappropriate. Results were synthesized and grouped by comparisons (e.g. diet vs. aerobic exercise, diet vs. diet + aerobic exercise etc.) and study design (long-term or weight loss/follow-up).

RESULTS

Forty percent of trials reported significantly greater long-term weight loss with diet compared with aerobic exercise, while results for differences in weight regain were inconclusive. Diet+aerobic exercise resulted in significantly greater weight loss than diet alone in 50% of trials. However, weight regain (∼ 55% of loss) was similar in diet and diet+aerobic exercise groups. Fat-free mass tended to be preserved when interventions included exercise.

Weight stigma is stressful. A review of evidence for the Cyclic Obesity/Weight-Based Stigma model

Weight stigma is highly pervasive, but its consequences are understudied. This review draws from theory in social psychology, health psychology, and neuroendocrinology to construct an original, generative model called the cyclic obesity/weight-based stigma (COBWEBS) model. This model characterizes weight stigma as a "vicious cycle" - a positive feedback loop wherein weight stigma begets weight gain. This happens through increased eating behavior and increased cortisol secretion governed by behavioral, emotional, and physiological mechanisms, which are theorized to ultimately result in weight gain and difficulty of weight loss. The purpose of this review is to evaluate the existing literature for evidence supporting such a model, propose ways in which individuals enter, fight against, and exit the cycle, and conclude by outlining fruitful future directions in this nascent yet important area of research.

Meal replacement based on Human Ration modulates metabolic risk factors during body weight loss: a randomized controlled trial

PURPOSE

A meal replacement may be an effective strategy in the management of obesity to increase antioxidant intake, attenuating oxidative stress and inflammation. In the present study, we investigated the efficacy of a new nutritional supplement to reduce metabolic risk parameters in obese women.

METHODS

In a randomized controlled crossover study (2 × 2), 22 women (percentage body fat 40.52 ± 3.75%; body mass index-BMI 28.72 ± 2.87 kg/m²; 35.04 ± 5.6 years old) were allocated into two treatments: hypocaloric diet and drink containing "Human Ration" (HR) consumption (CRHR), and hypocaloric diet and control drink consumption (CR). The study consisted of 2 periods of 5 weeks with 1 week of washout in two orders (CR → CRHR and CRHR → CR). Caloric restriction was 15%, based on estimated energy requirement. Anthropometric, clinical and metabolic risk parameters were assessed at baseline and at the end of each period.

RESULTS

Some metabolic risk factors were favorably modulated in both interventions: reduction in body weight (CR -0.74 ± 1.27 kg; p = 0.01; CRHR -0.77 ± 1.3 kg; p = 0.02), body mass index (BMI) (CR -0.27 ± 0.51 kg/m²; p = 0.02; CRHR -0.30 ± 0.52 kg/m²; p = 0.01) and HOMA-IR (CR -0.35 ± 0.82; p = 0.02, CRHR -0.41 ± 0.83; p = 0.03). However, CRHR reduced waist circumference (-2.54 ± 2.74 cm; p < 0.01) and gynoid fat (-0.264 ± 0.28 g; p < 0.01), and increased HDL-c levels (0.08 ± 0.15 mmol/l; p = 0.04).

CONCLUSION

Associated with hypocaloric diet, the intake of a nutritional supplement rich in phytochemicals as a breakfast substitute for 5 weeks had no additional effect on weight reduction than caloric restriction alone, but increased central lipolysis and improved the lipoprotein profile.

Effects of mild calorie restriction on anxiety and hypothalamic-pituitary-adrenal axis responses to stress in the male rat

Chronic calorie restriction (CR) is one of the few interventions to improve longevity and quality of life in a variety of species. It also reduces behavioral indices of anxiety and influences some stress hormones under basal conditions. However, it is not known how CR influences hypothalamic–pituitary–adrenal (HPA) axis function or if those on a CR diet have heightened HPA axis responses to stress. We hypothesized elevated basal glucocorticoid levels induced by CR would lead to exacerbated HPA axis responses to the psychological stress, restraint, in the male rat. We first confirmed rats fed 75% of their normal calorie intake for 3 weeks were less anxious than ad libitum‐fed (AD) rats in the elevated plus maze test for anxiety. The anxiolytic effect was mild, with only grooming significantly attenuated in the open field and no measured behavior affected in the light/dark box. Despite elevated basal glucocorticoids, CR rats had very similar hormonal and central responses to 15‐min restraint to the AD rats. Both CR and AD rats responded to restraint stress with a robust increase in glucocorticoids that was resolved by 60 min. Both groups also showed robust neuronal activation in the paraventricular nucleus of the hypothalamus and in other stress‐ and feeding‐sensitive brain regions that was not substantially affected by calorie intake. Our findings thus demonstrate chronic mild CR is subtly anxiolytic and is not likely to affect HPA axis responses to psychological stress. These findings support research suggesting a beneficial effect of mild CR.

Metabolic adaptation to weight loss: implications for the athlete

Optimized body composition provides a competitive advantage in a variety of sports. Weight reduction is common among athletes aiming to improve their strength-to-mass ratio, locomotive efficiency, or aesthetic appearance. Energy restriction is accompanied by changes in circulating hormones, mitochondrial efficiency, and energy expenditure that serve to minimize the energy deficit, attenuate weight loss, and promote weight regain. The current article reviews the metabolic adaptations observed with weight reduction and provides recommendations for successful weight reduction and long term reduced-weight maintenance in athletes.

Evaluating eating behavior treatments by FDA standards

Behavioral treatments for obesity are not evaluated by the same criteria as pharmaceutical drugs, even though treatments such as low-calorie dieting are widely prescribed, require patients' time and investment, and may have risks. The Food and Drug Administration (FDA) has a procedure for evaluating drugs, in which drugmakers must answer the following questions: (1) Is the treatment safe? (2) How dangerous is the condition the intervention is treating? (3) Is the treatment effective? (4) Is the treatment safe and effective for large numbers of people? We argue that using this framework to evaluate behavioral interventions could help identify unanswered research questions on their efficacy and effectiveness, and we use the example of low-calorie dieting to illustrate how FDA criteria might be applied in the context of behavioral medicine.

Characteristics of individuals who report present and past weight loss behaviours: results from a Canadian university community

PURPOSE

To characterise individuals who reported present and past weight loss behaviours on psycho-behavioural factors known to influence body weight, e.g. overeating, dietary restriction.

METHODS

An online questionnaire was distributed to a university community. Questions pertaining to present weight loss, previous weight loss, eating behaviour tendencies, perceived stress and sleep quality were answered by 3,069 individuals. Body weight and height were self-reported.

RESULTS

Present and past weight loss behaviours were prevalent in the sample, with 33.3 % of the participants who reported trying to lose weight, 33.1 % who reported having previously lost weight (>10 lbs), and 18.8 % who reported repeated weight loss behaviour (i.e. present and past weight loss behaviours). Trying to lose weight and previous weight loss were both independently associated with increased risk for psycho-behavioural characteristics known to be associated with obesity, e.g. overeating tendencies, perceived stress, short sleep duration. This risk was particularly elevated among the underweight/normal-weight individuals who reported repeated weight loss behaviours. Indeed, adjusted odds ratios for reporting restrictive and overeating tendencies, perceived stress and short sleep for these individuals were significantly higher compared to their underweight/normal-weight peers who did not report repeated weight loss behaviours (adjusted odds ratios 4.7, 2.7, 1.8, and 1.8, respectively, p < 0.01 to <0.0001).

CONCLUSIONS

Normal-weight individuals reporting weight loss behaviours are characterised by a psycho-behaviour profile which may further increase their risk of weight gain.

A school-based program implemented by community providers previously trained for the prevention of eating and weight-related problems in secondary-school adolescents: the MABIC study protocol

Background

The prevention of eating disorders and disordered eating are increasingly recognized as public health priorities. Challenges in this field included moving from efficacy to effectiveness and developing an integrated approach to the prevention of a broad spectrum of eating and weight-related problems. A previous efficacy trial indicated that a universal disordered eating prevention program, based on the social cognitive model, media literacy educational approach and cognitive dissonance theory, reduced risk factors for disordered eating, but it is unclear whether this program has effects under more real-world conditions. The main aim of this effectiveness trial protocol is to test whether this program has effects when incorporating an integrated approach to prevention and when previously-trained community providers implement the intervention.

Methods/design

The research design involved a multi-center non-randomized controlled trial with baseline, post and 1-year follow-up measures. Six schools from the city of Sabadell (close to Barcelona) participated in the intervention group, and eleven schools from four towns neighboring Sabadell participated in the control group. A total of 174 girls and 180 boys in the intervention group, and 484 girls and 490 boys in the control group were registered in class lists prior to baseline. A total of 18 community providers, secondary-school class tutors, nurses from the Catalan Government’s Health and School Program, and health promotion technicians from Sabadell City Council were trained and delivered the program. Shared risk factors of eating and weight-related problems were assessed as main measures.

Discussion

It will be vital for progress in disordered eating prevention to conduct effectiveness trials, which test whether interventions are effective when delivered by community providers under ecologically valid conditions, as opposed to tightly controlled research trials. The MABIC project will provide new contributions in this transition from efficacy to effectiveness and new data about progress in the integrated approach to prevention. Pending the results, the effectiveness trial meets the effectiveness standards set down by the Society for Prevention Research. This study will provide new evidence to improve and enhance disordered eating prevention programs.

Trial registration

Current Controlled Trials ISRCTN47682626

Biological mechanisms that promote weight regain following weight loss in obese humans

Weight loss dieting remains the treatment of choice for the vast majority of obese individuals, despite the limited long-term success of behavioral weight loss interventions. The reasons for the near universal unsustainability of behavioral weight loss in [formerly] obese individuals have not been fully elucidated, relegating researchers to making educated guesses about how to improve obesity treatment, as opposed to developing interventions targeting the causes of weight regain. This article discusses research on several factors that may contribute to weight regain following weight loss achieved through behavioral interventions, including adipose cellularity, endocrine function, energy metabolism, neural responsivity, and addiction-like neural mechanisms. All of these mechanisms are engaged prior to weight loss, suggesting that these so called "anti-starvation" mechanisms are activated via reductions in energy intake, rather than depletion of energy stores. Evidence suggests that these mechanisms are not necessarily part of a homeostatic feedback system designed to regulate body weight, or even anti-starvation mechanisms per se. Although they may have evolved to prevent starvation, they appear to be more accurately described as anti-weight loss mechanisms, engaged with caloric restriction irrespective of the adequacy of energy stores. It is hypothesized that these factors may combine to create a biological disposition that fosters the maintenance of an elevated body weight and works to restore the highest sustained body weight, thus precluding the long-term success of behavioral weight loss. It may be necessary to develop interventions that attenuate these biological mechanisms in order to achieve long-term weight reduction in obese individuals.

Lifelong caloric restriction increases working memory in mice

Caloric restriction (CR) is argued to positively affect general health, longevity and the normally occurring age-related reduction of cognition. This issue is well examined, but most studies investigated the effect of short-term periods of CR. Herein, 4 weeks old female mice were fed caloric restricted for 4, 20 and especially for 74 weeks. CR mice received 60% of food eaten by their ad libitum (AL) fed littermates, and all age-matched groups were behaviorally analyzed. The motor coordination, which was tested by rotarod/accelerod, decreased age-related, but was not influenced by the different periods of CR. In contrast, the age-related impairment of spontaneous locomotor activity and anxiety, both being evaluated by open field and by elevated plus maze test, was found aggravated by a lifelong CR. Measurement of cognitive performance with morris water maze showed that the working memory decreased age-related in AL mice, while a lifelong CR caused a better cognitive performance and resulted in a significantly better spatial memory upon 74 weeks CR feeding. However, a late-onset CR feeding in 66 weeks old mice did not ameliorate the working memory. Therefore, a lifelong CR seems to be necessary to improve working memory.

Is it stress? The role of stress related systems in chronic food restriction-induced augmentation of heroin seeking in the rat

Drug addiction is a chronic disease characterized by recurring episodes of abstinence and relapse. The precise mechanisms underlying this pattern are yet to be elucidated, but stress is thought to be a major factor in relapse. Recently, we reported that rats under withdrawal and exposed to a mild chronic stressor, prolonged food restriction, show increased heroin seeking compared to sated controls. Previous studies demonstrated a critical role for corticotropin-releasing factor (CRF) and corticosterone, hormones involved in the stress response, in acute food deprivation-induced reinstatement of extinguished drug seeking. However, the role of CRF and corticosterone in chronic food restriction-induced augmentation of drug seeking remains unknown. Here, male Long-Evans rats were trained to self-administer heroin for 10 days in operant conditioning chambers. Rats were then removed from the training chambers, and subjected to 14 days of unrestricted (sated rats) or a mildly restricted (FDR rats) access to food, which maintained their body weight (BW) at 90% of their baseline weight. On day 14, different groups of rats were administered a selective CRF₁ receptor antagonist (R121919; 0.0, 20.0 mg/kg; s.c.), a non-selective CRF receptor antagonist (α-helical CRF; 0.0, 10.0, 25.0 μg/rat; i.c.v.) or a glucocorticoid receptor antagonist (RU486; 0.0, 30.0 mg/kg; i.p.), and underwent a 1 h drug seeking test under extinction conditions. An additional group of rats was tested following adrenalectomy. All FDR rats showed a statistically significant increase in heroin seeking compared to the sated rats. No statistically significant effects for treatment with α-helical CRF, R121919, RU486 or adrenalectomy were observed. These findings suggest that stress may not be a critical factor in the augmentation of heroin seeking in food-restricted rats.

Mechanisms of Weight Regain following Weight Loss

Obesity is a world-wide pandemic and its incidence is on the rise along with associated comorbidities. Currently, there are few effective therapies to combat obesity. The use of lifestyle modification therapy, namely, improvements in diet and exercise, is preferable over bariatric surgery or pharmacotherapy due to surgical risks and issues with drug efficacy and safety. Although they are initially successful in producing weight loss, such lifestyle intervention strategies are generally unsuccessful in achieving long-term weight maintenance, with the vast majority of obese patients regaining their lost weight during followup. Recently, various compensatory mechanisms have been elucidated by which the body may oppose new weight loss, and this compensation may result in weight regain back to the obese baseline. The present review summarizes the available evidence on these compensatory mechanisms, with a focus on weight loss-induced changes in energy expenditure, neuroendocrine pathways, nutrient metabolism, and gut physiology. These findings have added a major focus to the field of antiobesity research. In addition to investigating pathways that induce weight loss, the present work also focuses on pathways that may instead prevent weight regain. Such strategies will be necessary for improving long-term weight loss maintenance and outcomes for patients who struggle with obesity.

The defence of body weight: a physiological basis for weight regain after weight loss

Although weight loss can usually be achieved by restricting food intake, the majority of dieters regain weight over the long-term. In the hypothalamus, hormonal signals from the gastrointestinal tract, adipose tissue and other peripheral sites are integrated to influence appetite and energy expenditure. Diet-induced weight loss is accompanied by several physiological changes which encourage weight regain, including alterations in energy expenditure, substrate metabolism and hormone pathways involved in appetite regulation, many of which persist beyond the initial weight loss period. Safe effective long-term strategies to overcome these physiological changes are needed to help facilitate maintenance of weight loss. The present review, which focuses on data from human studies, begins with an outline of body weight regulation to provide the context for the subsequent discussion of short- and long-term physiological changes which accompany diet-induced weight loss.

Dairy food consumption and meal-induced cortisol response interacted to influence weight loss in overweight women undergoing a 12-week, meal-controlled, weight loss intervention

Dairy food enhances weight loss in animal models, possibly by modifying the metabolic effects of cortisol. This study determined in overweight women (ages 20.0-45.9 y; n = 51) whether including dairy food in an energy-restricted diet affects cortisol concentrations and whether differences in provoked cortisol explain the magnitude of weight loss. Women received either an adequate amount of dairy food (AD), the equivalent of ≥711 mL/d milk, or a low amount of dairy food (LD), the equivalent to ≤238 mL/d milk, in a 12-wk, energy-restricted dietary intervention. Participants were tested in a 12-h laboratory visit, which included 2 standard meals and a dinner buffet that was consumed ad libitum. Salivary cortisol was measured from waking to bedtime. Energy restriction increased (P ≤ 0.04) the minimum and decreased (P ≤ 0.02) the diurnal amplitude in the salivary cortisol concentration from baseline to postintervention. Energy restriction enhanced the dinner meal-stimulated salivary cortisol response (DMR) (P ≤ 0.02) but only in the LD group. Compared with the LD treatment, the AD treatment induced (P ≤ 0.04) greater reductions in body weight and fat, but only in women characterized as having a baseline DMR (responders) (n = 26); weight and fat lost in the AD and LD groups were similar in nonresponders (n = 25). Overall, energy restriction dampened diurnal salivary cortisol fluctuations [symptomatic of hypothalamic-pituitary-adrenal (HPA) axis dysfunction] and enhanced dinner meal-stimulated salivary cortisol concentrations. The AD treatment prevented the latter. Furthermore, certain phenotypic markers of HPA axis function may help to expose the weight-reducing effects of consuming dairy food.

The effects of chronic food restriction on cue-induced heroin seeking in abstinent male rats

RATIONALE AND OBJECTIVES

Previous research with an animal model of relapse has shown that acute food deprivation will reinstate extinguished drug seeking. Recent evidence with humans, however, suggests that chronic food restriction rather than acute food deprivation is related to increases in drug taking and relapse, emphasizing a need for an animal model to elucidate the neural mechanisms mediating the effects of chronic food restriction on drug seeking. Here we studied the effects of chronic food restriction during a period of abstinence on heroin seeking in rats.

METHODS

Rats were trained to self-administer heroin over 10 days (0.1 mg/kg/infusion; i.v.). Rats were then removed from the operant conditioning chambers and exposed to a mild food restriction (resulting in 10-15 % decrease in body weight) or given unrestricted access to food for 14 days while abstinent. The abstinence period was followed by a drug-seeking test under extinction conditions. Subsequent experiments manipulated the length of restriction and test conditions.

RESULTS

Rats that were food restricted throughout the abstinence period demonstrated a robust increase in cue-induced heroin seeking compared to sated rats. Re-feeding prior to testing or decreasing the length of the food restriction period prevented the augmentation of drug seeking.

CONCLUSIONS

A combination of chronic food restriction and a concurrent state of hunger appears to be necessary for an increase in cue-induced heroin seeking following abstinence. The procedure presented here may serve as a useful model to study the increased risk for relapse following dietary manipulations in abstinent subjects.

Bone metabolism in obesity and weight loss

Excess body weight due to obesity has traditionally been considered to have a positive effect on bone; however, more recent findings suggest that bone quality is compromised. Both obesity and caloric restriction increase fracture risk and are regulated by endocrine factors and cytokines that have direct and indirect effects on bone and calcium absorption. Weight reduction will decrease bone mass and mineral density, but this varies by the individual's age, gender, and adiposity. Dietary modifications, exercise, and medications have been shown to attenuate the bone loss associated with weight reduction. Future obesity and weight loss trials would benefit from assessment of key hormones, adipokine and gut peptides that regulate calcium absorption, and bone mineral density and quality by using sensitive techniques in high-risk populations.

Food insecurity and mental disorders in a national sample of U.S. adolescents

OBJECTIVE

To examine whether food insecurity is associated with past-year DSM-IV mental disorders after controlling for standard indicators of family socioeconomic status (SES) in a U.S. national sample of adolescents.

METHOD

Data were drawn from 6,483 adolescent-parent pairs who participated in the National Comorbidity Survey Replication Adolescent Supplement, a national survey of adolescents 13 to 17 years old. Frequency and severity of food insecurity were assessed with questions based on the U.S. Department of Agriculture's Food Security Scale (standardized to a mean of 0, variance of 1). DSM-IV mental disorders were assessed with the World Health Organization Composite International Diagnostic Interview. Associations of food insecurity with DSM-IV/Composite International Diagnostic Interview diagnoses were estimated with logistic regression models controlling for family SES (parental education, household income, relative deprivation, community-level inequality, and subjective social status).

RESULTS

Food insecurity was highest in adolescents with the lowest SES. Controlling simultaneously for other aspects of SES, standardized food insecurity was associated with an increased odds of past-year mood, anxiety, behavior, and substance disorders. A 1 standard deviation increase in food insecurity was associated with a 14% increase in the odds of past-year mental disorder, even after controlling for extreme poverty. The association between food insecurity and mood disorders was strongest in adolescents living in families with a low household income and high relative deprivation.

CONCLUSIONS

Food insecurity is associated with a wide range of adolescent mental disorders independently of other aspects of SES. Expansion of social programs aimed at decreasing family economic strain might be one useful policy approach for improving youth mental health.

Low-calorie diet induced weight loss may alter regulatory hormones and contribute to rebound visceral adiposity in obese persons with a family history of type-2 diabetes

PURPOSE

To examine potential detrimental long-term effects of acute diet-induced weight loss on visceral adiposity, insulin resistance, cortisol, and adipokines in obese individuals at risk for type-2 diabetes.

DATA SOURCES

Anthropometric measures (height, weight, waist circumference), self-report instruments, abdominal computed tomography (CT) scan, and blood samples (glucose, insulin, interleukin-6, leptin, adiponectin) were obtained from a convenience sample of 20 participants at baseline, after a 28-day low-calorie diet (800 kcal/day) intervention, and again 6 months later.

CONCLUSIONS

Fifteen of 20 participants completed the 28-day diet intervention and had a mean weight loss of 15 pounds. Comparison between baseline, postdiet, and 6-month data, demonstrated that although participants had significant improvements after the diet, they regained fat mass, particularly in the visceral area.

IMPLICATIONS FOR PRACTICE

Clinicians may need to revise recommendations for using low-calorie diets to achieve weight loss. Diet-induced weight cycling may contribute to dysregulation of metabolism and have long-term detrimental consequences for accumulation of visceral adipose tissue. The likelihood of success is low, with high dropout rates, and those patients who achieve weight loss are very likely to regain it. Thus, the perceived short-term benefits of calorie-restricted diets in this population likely do not outweigh the potential long-term detrimental effects.

Unhealthy weight-control behaviours, dieting and weight status: a cross-cultural comparison between North American and Spanish adolescents

The aim of the current study was to examine and compare dieting and unhealthy weight-control behaviours (UWCB) in population-based samples in two large urban areas in Spain (Barcelona) and in the USA (Twin Cities of Minneapolis and St. Paul, Minnesota). Additionally, use of UWCB across weight categories was explored in both samples. Participants included 1501 adolescents from Barcelona (48% girls, 52% boys) and 2793 adolescents from the Twin Cities (53% girls, 47% boys). The main outcome measures were dieting, UWCB (less extreme and extreme) and weight status. Although dieting and UWCB were prevalent in both samples, particularly among girls, the prevalence was higher in the US sample. In both countries, the report of dieting and use of UWCB was highest among overweight and obese youth. Prevention interventions that address the broad spectrum of eating and weight-related problems should be warranted in light of the high prevalence and co-occurrence of overweight and unhealthy weight-related behaviours.

Obesity: a disease or a biological adaptation? An update

Obesity is characterized by the accumulation of excess body fat and can be conceptualized as the physical manifestation of chronic energy excess. An important challenge of today's world is that our so-called obesogenic environment is conducive to the consumption of energy and unfavourable to the expenditure of energy. The modern, computer-dependent, sleep-deprived, physically inactive humans live chronically stressed in a society of food abundance. From a physiological standpoint, the excess weight gain observed in prone individuals is perceived as a normal consequence to a changed environment rather than a pathological process. In other words, weight gain is a sign of our contemporary way of living or a 'collateral damage' in the physiological struggle against modernity. Additionally, substantial body fat loss can complicate appetite control, decrease energy expenditure to a greater extent than predicted, increase the proneness to hypoglycaemia and its related risk towards depressive symptoms, increase the plasma and tissue levels of persistent organic pollutants that promote hormone disruption and metabolic complications, all of which are adaptations that can increase the risk of weight regain. In contrast, body fat gain generally provides the opposite adaptations, emphasizing that obesity may realistically be perceived as an a priori biological adaptation for most individuals. Accordingly, prevention and treatment strategies for obesity should ideally target the main drivers or root causes of body fat gain in order to be able to improve the health of the population.

Calorie restriction reduces psychological stress reactivity and its association with brain volume and microstructure in aged rhesus monkeys

BACKGROUND

Heightened stress reactivity is associated with hippocampal atrophy, age-related cognitive deficits, and increased risk for Alzheimer's disease. This temperament predisposition may aggravate age-associated brain pathology or be reflective of it. This association may be mediated through repeated activation of the stress hormone axis over time. Dietary interventions, such as calorie restriction (CR), affect stress biology and may moderate the pathogenic relationship between stress reactivity and brain in limbic and prefrontal regions.

METHODS

Rhesus monkeys (Macaca mulatta) aged 19-31 years consumed either a standard diet (N=18) or were maintained on 30% CR relative to baseline intake (N=26) for 13-19 years. Behavior was rated in both normative and aversive contexts. Urinary cortisol was collected. Animals underwent magnetic resonance imaging and diffusion tensor imaging (DTI) to acquire volumetric and tissue microstructure data respectively. Voxel-wise statistics regressed a global stress reactivity factor, cortisol, and their interaction on brain indices across and between dietary groups.

RESULTS

CR significantly reduced stress reactivity during aversive contexts without affecting activity, orientation, or attention behavior. Stress reactivity was associated with less volume and tissue density in areas important for emotional regulation and the endocrine axis including prefrontal cortices, hippocampus, amygdala, and hypothalamus. CR reduced these relationships. A Cortisol by Stress Reactivity voxel-wise interaction indicated that only monkeys with high stress reactivity and high basal cortisol demonstrated lower brain volume and tissue density in prefrontal cortices, hippocampus, and amygdala.

CONCLUSIONS

High stress reactivity predicted lower volume and microstructural tissue density in regions involved in emotional processing and modulation. A CR diet reduced stress reactivity and regional associations with neural modalities. High levels of cortisol appear to mediate some of these relationships.

Biology's response to dieting: the impetus for weight regain

Dieting is the most common approach to losing weight for the majority of obese and overweight individuals. Restricting intake leads to weight loss in the short term, but, by itself, dieting has a relatively poor success rate for long-term weight reduction. Most obese people eventually regain the weight they have worked so hard to lose. Weight regain has emerged as one of the most significant obstacles for obesity therapeutics, undoubtedly perpetuating the epidemic of excess weight that now affects more than 60% of U.S. adults. In this review, we summarize the evidence of biology's role in the problem of weight regain. Biology's impact is first placed in context with other pressures known to affect body weight. Then, the biological adaptations to an energy-restricted, low-fat diet that are known to occur in the overweight and obese are reviewed, and an integrative picture of energy homeostasis after long-term weight reduction and during weight regain is presented. Finally, a novel model is proposed to explain the persistence of the "energy depletion" signal during the dynamic metabolic state of weight regain, when traditional adiposity signals no longer reflect stored energy in the periphery. The preponderance of evidence would suggest that the biological response to weight loss involves comprehensive, persistent, and redundant adaptations in energy homeostasis and that these adaptations underlie the high recidivism rate in obesity therapeutics. To be successful in the long term, our strategies for preventing weight regain may need to be just as comprehensive, persistent, and redundant, as the biological adaptations they are attempting to counter.

A review of weight control strategies and their effects on the regulation of hormonal balance

The estimated prevalence of obesity in the USA is 72.5 million adults with costs attributed to obesity more than 147 billion dollars per year. Though caloric restriction has been used extensively in weight control studies, short-term success has been difficult to achieve, with long-term success of weight control being even more elusive. Therefore, novel approaches are needed to control the rates of obesity that are occurring globally. The purpose of this paper is to provide a synopsis of how exercise, sleep, psychological stress, and meal frequency and composition affect levels of ghrelin, cortisol, insulin GLP-1, and leptin and weight control. We will provide information regarding how hormones respond to various lifestyle factors which may affect appetite control, hunger, satiety, and weight control.

Performance on the Iowa Gambling Task is related to magnitude of weight loss and salivary cortisol in a diet-induced weight loss intervention in overweight women

The overall objective of this study was to examine the relationship between executive function, specifically decision-making, and weight loss. We used the Iowa Gambling Task (IGT) to characterize decision-making and compared performance on this task to weight loss in obese women (n=29) participating in a 12-week controlled, calorie-reduced intervention. We hypothesized that a greater amount of weight loss over the course of the intervention would be associated with better performance on the IGT, assessed at the end of the intervention. The intervention led to significant weight loss of 5.8±3.1 kg (p<0.05) and fat loss of 5.1±3.0 kg (p<0.05). Body weight and fat mass losses over the 12-week intervention varied widely, ranging from -12.5 kg to 0.0 kg for body weight and -10.4 kg to +0.8 kg for fat mass. A greater amount of body weight loss was correlated (r=0.425; p<0.01) with a higher total score on the IGT. Similarly, the reduction in body fat mass was also correlated with the IGT score (r=0.408; p<0.05). We examined other physiological (salivary cortisol), metabolic (resting energy expenditure), and behavioral (food intake; dietary restraint) factors that might be related to differences in the magnitude of weight loss. Of these variables, ad libitum consumption of energy, fat and protein during a buffet meal was inversely related to weight loss (r=-0.428; p<0.05; r=-0.375; p<0.05 and r=-0.472; p=0.01, respectively). The present study is the first to report an association between diet-induced weight loss and performance on the IGT, and this association was specific to the loss of body fat. Our results suggest that differences in weight loss may be linked to executive function that involves decision-making about events that have emotionally or socially salient ramifications. These findings underscore the need to further investigate higher cognitive and neuroendocrine pathways that may influence or be altered by the process of dieting and weight loss.

Weight science: evaluating the evidence for a paradigm shift

Current guidelines recommend that "overweight" and "obese" individuals lose weight through engaging in lifestyle modification involving diet, exercise and other behavior change. This approach reliably induces short term weight loss, but the majority of individuals are unable to maintain weight loss over the long term and do not achieve the putative benefits of improved morbidity and mortality. Concern has arisen that this weight focus is not only ineffective at producing thinner, healthier bodies, but may also have unintended consequences, contributing to food and body preoccupation, repeated cycles of weight loss and regain, distraction from other personal health goals and wider health determinants, reduced self-esteem, eating disorders, other health decrement, and weight stigmatization and discrimination. This concern has drawn increased attention to the ethical implications of recommending treatment that may be ineffective or damaging. A growing trans-disciplinary movement called Health at Every Size (HAES) challenges the value of promoting weight loss and dieting behavior and argues for a shift in focus to weight-neutral outcomes. Randomized controlled clinical trials indicate that a HAES approach is associated with statistically and clinically relevant improvements in physiological measures (e.g., blood pressure, blood lipids), health behaviors (e.g., eating and activity habits, dietary quality), and psychosocial outcomes (such as self-esteem and body image), and that HAES achieves these health outcomes more successfully than weight loss treatment and without the contraindications associated with a weight focus. This paper evaluates the evidence and rationale that justifies shifting the health care paradigm from a conventional weight focus to HAES.