Nonhomeostatic control of human appetite and physical activity in regulation of energy balance. Exerc Sport Sci Rev. 2010;38:114-121. [PMID: 20577059 DOI: 10.1097/JES.0b013e3181e3728f]

Use of a brief, retrospective Comprehensive Feeding Practices Questionnaire in a bariatric-surgery seeking adult population

Parental feeding practices in childhood have been shown to contribute to childhood eating habits, behaviors, and weight status. Less understood is the longitudinal impact of parental feeding practices on these variables in adulthood. Therefore, the aim of the present work was to validate a modified, brief, Comprehensive Feeding Practices Questionnaire (CFPQ) reformatted to account for retrospective recollections of parental feeding practices experienced in childhood among a sample of adults with obesity. Adults (n = 719, mean age = 44.3 years, mean BMI = 47.1 kg/m²) completed a modified, brief, retrospective CFPQ containing seven pre-defined subscales of the original CFPQ. Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) procedures were used to evaluate survey factor structure and associations with gender, BMI, and self-reported race. An EFA derived six-factor model demonstrated better model fit and reliability than the originally proposed seven-factor model. Gender and self-reported race were not correlated with subscales of the brief, retrospective, CFPQ, while BMI was positively correlated with the Food as Reward subscale. This six-factor, brief, retrospective, CFPQ can be used to provide insight into the potential origins of individual eating behaviors, and warrants use in future work attempting to clarify the relationships between parental feeding practices and eating behaviors in adulthood.

Why We Eat Too Much, Have an Easier Time Gaining Than Losing Weight, and Expend Too Little Energy: Suggestions for Counteracting or Mitigating These Problems

The intent of this review is to survey physiological, psychological, and societal obstacles to the control of eating and body weight maintenance and offer some evidence-based solutions. Physiological obstacles are genetic and therefore not amenable to direct abatement. They include an absence of feedback control against gaining weight; a non-homeostatic relationship between motivations to be physically active and weight gain; dependence of hunger and satiation on the volume of food ingested by mouth and processed by the gastrointestinal tract and not on circulating metabolites and putative hunger or satiation hormones. Further, stomach size increases from overeating and binging, and there is difficulty in maintaining weight reductions due to a decline in resting metabolism, increased hunger, and enhanced efficiency of energy storage. Finally, we bear the evolutionary burden of extraordinary human capacity to store body fat. Of the psychological barriers, human craving for palatable food, tendency to overeat in company of others, and gullibility to overeat when offered large portions, can be overcome consciously. The tendency to eat an unnecessary number of meals during the wakeful period can be mitigated by time-restricted feeding to a 6-10 hour period. Social barriers of replacing individual physical work by labor-saving appliances, designing built environments more suitable for car than active transportation; government food macronutrient advice that increases insulin resistance; overabundance of inexpensive food; and profit-driven efforts by the food industry to market energy-dense and nutritionally compromised food are best overcome by informed individual macronutrient choices and appropriate timing of exercise with respect to meals, both of which can decrease insulin resistance. The best defense against overeating, weight gain, and inactivity is the understanding of factors eliciting them and of strategies that can avoid and mitigate them.

Simple Energy Balance or Microbiome for Childhood Obesity Prevention?

Obesity prevention interventions generally have either not worked or had effects inadequate to mitigate the problem. They have been predicated on the simple energy balance model, which has been severely questioned by biological scientists. Numerous other etiological mechanisms have been proposed, including the intestinal microbiome, which has been related to childhood obesity in numerous ways. Public health research is needed in regard to diet and the microbiome, which hopefully will lead to effective child obesity prevention.

Associations Between Habitual School-Day Breakfast Consumption Frequency and Academic Performance in British Adolescents

Studies indicate that breakfast positively affects learning in children. The present study aimed to examine associations between habitual school-day breakfast consumption frequency and academic performance, as measured by the General Certificate of Secondary Education (GCSE). The GCSE is a national academic qualification obtained by most British children during secondary education. Adolescents aged 16-18 years (n = 294; females: 77.2%) completed a retrospective 7-day food diary to report breakfast intake and a questionnaire to report GCSE grades. Breakfast was defined as any food or drink containing ≥5% of total energy expenditure (TEE) consumed up to 10:00 a.m. on school days. Habitual weekly school-day breakfast consumption frequency was categorized as rare (0-1 school days), occasional (2-3 school days), or frequent (4-5 school days). GCSE grades were aggregated into point scores and linear regression models were applied. Participants' GCSE grades in Mathematics and English were analyzed using ordinal logistic regression. Adolescents who rarely consumed breakfast on school days had a significantly lower capped point score (β = -0.13, p < 0.05) and mean point score (β = -0.14, p < 0.05) compared with frequent consumers. Low/middle socio-economic status (SES) adolescents who rarely consumed breakfast were significantly less likely to achieve higher Mathematics grades compared to low/middle SES adolescents who frequently consumed breakfast [adjusted cumulative odds ratio (OR): 0.35 95% confidence interval (CI): 0.17-0.72]. This cross-sectional study demonstrates that habitual school-day breakfast consumption amongst adolescents is a significant correlate of GCSE attainment. The results offer promising associative evidence which warrants further exploration in well controlled studies.

Understanding Human Physiological Limitations and Societal Pressures in Favor of Overeating Helps to Avoid Obesity

Fat gain in our United States (US) environment of over-abundant, convenient, and palatable food is associated with hypertension, cardiovascular disease, diabetes, and increased mortality. Fuller understanding of physiological and environmental challenges to healthy weight maintenance could help prevent these morbidities. Human physiological limitations that permit development of obesity include a predilection to overeat palatable diets, inability to directly detect energy eaten or expended, a large capacity for fat storage, and the difficulty of losing body fat. Innate defenses resisting fat loss include reduced resting metabolism, increased hunger, and high insulin sensitivity, promoting a regain of fat, glycogen, and lean mass. Environmental challenges include readily available and heavily advertised palatable foods, policies and practices that make them abundant, less-than-ideal recommendations regarding national dietary macronutrient intake, and a frequently sedentary lifestyle. After gaining excess fat, some metabolic burdens can be mitigated though thoughtful selection of nutrients. Reduced dietary salt helps lower hypertension, less dietary sugar lowers risk of cardiovascular disease and obesity, and reducing proportion of dietary carbohydrates lowers post-meal insulin secretion and insulin resistance. Food intake and exercise should also be considered thoughtfully, as exercise in a fasted state and before the meals raises glucose intolerance, while exercising shortly after eating lowers it. In summary, we cannot directly detect energy eaten or expended, we have a genetic predisposition to eat palatable diets even when not hungry, and we have a large capacity for fat storage and a difficult time permanently losing excess fat. Understanding this empowers individuals to avoid overeating and helps them avoid obesity.

Altered baseline brain activity differentiates regional mechanisms subserving biological and psychological alterations in obese men

Obesity as a chronic disease is a major factor for insulin resistance and Type 2 diabetes, which has become a global health problem. In the present study, we used resting state functional MRI to investigate the amplitude of low frequency fluctuations of spontaneous signal during both hunger and satiety states in 20 lean and 20 obese males. We found that, before food intake, obese men had significantly greater baseline activity in the precuneus and lesser activity in dorsal anterior cingulate cortex (dACC) relative to lean subjects. Furthermore, after food intake, obese males had significantly lesser activity in dACC than lean males. We further found a significant positive correlation between precuneus activation and hunger ratings before food intake, while dACC activity was negatively correlated with plasma insulin levels before and after food intake. These results indicated that both precuneus and dACC may play an important role in eating behavior. While precuneus rather seemed to mediate subjective satiety, dACC levels rather reflected indirect measures of glucose utilization.

Counterregulation of insulin by leptin as key component of autonomic regulation of body weight

A re-examination of the mechanism controlling eating, locomotion, and metabolism prompts formulation of a new explanatory model containing five features: a coordinating joint role of the (1) autonomic nervous system (ANS); (2) the suprachiasmatic (SCN) master clock in counterbalancing parasympathetic digestive and absorptive functions and feeding with sympathetic locomotor and thermogenic energy expenditure within a circadian framework; (3) interaction of the ANS/SCN command with brain substrates of reward encompassing dopaminergic projections to ventral striatum and limbic and cortical forebrain. These drive the nonhomeostatic feeding and locomotor motivated behaviors in interaction with circulating ghrelin and lateral hypothalamic neurons signaling through melanin concentrating hormone and orexin-hypocretin peptides; (4) counterregulation of insulin by leptin of both gastric and adipose tissue origin through: potentiation by leptin of cholecystokinin-mediated satiation, inhibition of insulin secretion, suppression of insulin lipogenesis by leptin lipolysis, and modulation of peripheral tissue and brain sensitivity to insulin action. Thus weight-loss induced hypoleptimia raises insulin sensitivity and promotes its parasympathetic anabolic actions while obesity-induced hyperleptinemia supresses insulin lipogenic action; and (5) inhibition by leptin of bone mineral accrual suggesting that leptin may contribute to the maintenance of stability of skeletal, lean-body, as well as adipose tissue masses.

Striatal enkephalinergic differences in rats selectively bred for intrinsic running capacity

Rats selectively bred for high- and low-capacity for running on a treadmill (HCR; LCR) also differ in wheel-running behavior, but whether wheel-running can be explained by intrinsic or adaptive brain mechanisms is not as yet understood. It is established that motivation of locomotory behavior is driven by dopaminergic transmission in mesolimbic and mesostriatal systems. However, whether voluntary wheel running is associated with enkephalinergic activity in the ventral striatum is not known.

MATERIALS AND METHODS

40 male (20 HCR and 20 LCR) and 40 female (20 HCR and 20 LCR) rats were randomly assigned to 3 weeks of activity wheel exposure or sedentary conditions without wheel access. After 3 weeks of activity-wheel running, rats were decapitated and brains were extracted. Coronal sections were analyzed utilizing in situ hybridization histochemistry for enkephalin (ENK) mRNA in the ventral striatum.

RESULTS

HCR rats expressed less ENK than LCR rats in the nucleus accumbens among females (p<0.01) and in the olfactory tubercle among both females (p<0.05) and males (p<0.05). There was no effect of wheel running on ENK mRNA expression.

CONCLUSION

Line differences in ENK expression in the olfactory tubercle, and possibly the nucleus accumbens, partly explain divergent wheel-running behavior. The lower striatal ENK in the HCR line is consistent with enhanced dopaminergic tone, which may explain the increased motivation for wheel running observed in the HCR line.

Immediate neural responses of appetitive motives and its relationship with hedonic appetite and body weight as revealed by magnetoencephalography

Background

We aimed to determine the brain areas related to food motivation and to examine individual variability using magnetoencephalography (MEG) during a fasted state. Correlation analysis was performed between MEG responses and the subscale and aggregated scores of the Power of Food Scale (PFS) and body mass index (BMI).

Material/Methods

Eight healthy, right-handed males [age, 29.0±10.4 years; BMI, 22.7±2.4 kg/m² (mean ±SD)] were enrolled. The MEG experiment consisted of 2 food sessions and 2 control sessions in an alternating and counterbalanced order. During the MEG recordings, participants viewed a set of food pictures (food session) or mosaic pictures (control session) projected on a screen.

Results

When participants viewed pictures of food items, we were able to estimate equivalent current dipoles (ECDs) in the insular cortex in all participants peaked approximately 300 ms after the onset of each picture presentation. When they viewed mosaic pictures, 1 of 8 participants exhibited corresponding ECDs. Of note, significant correlations were observed between the intensities of the MEG responses and the subscale scores of Factor 1 (food available) (r=0.846, P=0.008) and those of Factor 2 (food present) (r=0.875, P=0.004), the aggregated scores of PFS (r=0.820, P=0.013), and BMI (r=0.898, P=0.002).

Conclusions

We demonstrated the involvement of the immediate neural responses of the insular cortex in individual differences in appetitive motivation. The signal intensities of the insular cortex were associated with self-awareness of appetitive motive.

Exercise and ghrelin. A narrative overview of research

Since its discovery in 1999, ghrelin has been implicated in a multiplicity of physiological activities. Most notably, ghrelin has an important influence on energy metabolism and after the identification of its potent appetite stimulating effects ghrelin has been termed the 'hunger hormone'. Exercise is a stimulus which has a significant impact on energy homeostasis and consequently a substantial body of research has investigated the interaction between exercise and ghrelin. This narrative review provides an overview of research relating to the acute and chronic effects of exercise on circulating ghrelin (acylated, unacylated and total). To enhance study comparability, the scope of this review is limited to research undertaken in adult humans and consequently studies involving children and animals are not discussed. Although there is significant ambiguity within much of the early research, our review suggests that acute exercise transiently interferes with the production of acylated ghrelin. Furthermore, the consensus of evidence indicates that exercise training does not influence circulating ghrelin independent of weight loss. Additional research is needed to verify and extend the available literature, particularly by uncovering the mechanisms governing acute exercise-related changes and characterising responses in other populations such as females, older adults, and the obese.

Overview of bariatric surgery for the physician

The worldwide pandemic of obesity carries alarming health and socioeconomic implications. Bariatric surgery is currently the only effective treatment for severe obesity. It is safe, with mortality comparable to that of cholecystectomy, and effective in producing substantial and sustainable weight loss, along with high rates of resolution of associated comorbidities, including type 2 diabetes. For this reason, indications for bariatric surgery are being widened. In addition to volume restriction and malabsorption, bariatric surgery brings about neurohormonal changes that affect satiety and glucose homeostasis. Increased understanding of these mechanisms will help realise therapeutic benefits by pharmacological means. Bariatric surgery improves long-term mortality but can cause long-term nutritional deficiencies. The safety of pregnancy after bariatric surgery is still being elucidated.

The effects of weight loss strategies on gastric emptying and appetite control

The gastrointestinal tract plays an important role in the improved appetite control and weight loss in response to bariatric surgery. Other strategies which similarly alter gastrointestinal responses to food intake could contribute to successful weight management. The aim of this review is to discuss the effects of surgical, pharmacological and behavioural weight loss interventions on gastrointestinal targets of appetite control, including gastric emptying. Gastrointestinal peptides are also discussed because of their integrative relationship in appetite control. This review shows that different strategies exert diverse effects and there is no consensus on the optimal strategy for manipulating gastric emptying to improve appetite control. Emerging evidence from surgical procedures (e.g. sleeve gastrectomy and Roux-en-Y gastric bypass) suggests a faster emptying rate and earlier delivery of nutrients to the distal small intestine may improve appetite control. Energy restriction slows gastric emptying, while the effect of exercise-induced weight loss on gastric emptying remains to be established. The limited evidence suggests that chronic exercise is associated with faster gastric emptying, which we hypothesize will impact on appetite control and energy balance. Understanding how behavioural weight loss interventions (e.g. diet and exercise) alter gastrointestinal targets of appetite control may be important to improve their success in weight management.

Physical activity and weight control: conflicting findings

PURPOSE OF REVIEW

It is often hypothesized that increasing the volume of physical activity in the American lifestyle will slow and possibly even reverse the epidemic of obesity. Herein, we review the evidence pertaining to the role of physical activity in weight control from interventions performed in adults.

RECENT FINDINGS

Evidence exists both for and against the role of physical activity in weight control. High levels of physical activity and successful maintenance of body weight may be a result of better coupling between energy intake and energy expenditure, potentially mediated by physiological changes in appetite, albeit in the presence of large interindividual variability. Prospective studies, however, find little evidence of the more physically active members of a population gaining less excess weight than those who are the least physically active.

SUMMARY

When considering the impact of physical activity on body weight regulation, it is important to keep in mind that there are multiple hormones that acutely suppress (or stimulate) food intake and that the integration of these signals influence overall energy balance in a manner that is not yet fully understood. Moreover, cognitive and social influences may override these signals. Even though the impact of physical activity for weight control is still controversial, little doubt exists that increasing regular physical activity, particularly energy expended during structured exercise, is important for improving physical fitness and cardiovascular health.

Intensive exercise: a remedy for childhood obesity?

BACKGROUND

Acute exercise can affect the energy intake regulation, which is of major interest in terms of obesity intervention and weight loss.

OBJECTIVE

To test the hypothesis that intensive exercise can affect the subsequent energy intake and balance in obese adolescents.

DESIGN

The study was conducted in 2009 and enrolled 12 obese pubertal adolescents ages 14.4±1.5 years old. Two exercise and one sedentary sessions were completed. The first exercise (EX(1)) and sedentary session (SED) were randomly conducted 1 week apart. The second exercise session (EX₂) was conducted following 6 weeks of diet modification and physical activity (3×90 min/week) to produce weight loss. Energy intake was recorded, subjective appetite sensation was evaluated using Visual Analogue Scales and energy expenditure was measured using ActiHerats during EX(1), EX₂ and SED.

RESULTS

Total energy intake over the awakened period was significantly reduced by 31% and 18% during the EX(1) and EX(2) sessions compared with the SED session, respectively (p<0.01). Energy balance over the awakened period was negative during EX₁, neutral during EX₂ and positive during SED. There was no significant difference in terms of subjective appetite rates between sessions during the awakened hours.

CONCLUSIONS

Intensive exercise favors a negative energy balance by dually affecting energy expenditure and energy intake without changes in appetite sensations, suggesting that adolescents are not at risk of food frustration.