The importance of fat-free mass and constituent tissue-organs in the control of human appetite.

PURPOSE OF REVIEW: Traditional models of human appetite focus on the contribution of adipose tissue and the gastrointestinal tract, both of which exert mainly inhibitory influences. The purpose of this review is to consider the biological factors that influence the drive to eat. RECENT FINDINGS: Fat-free mass is positively associated with objectively measured meal size and daily energy intake. These findings have been replicated in multiple populations across the life-course in laboratory and free-living studies. Studies have shown that the effect of fat-free mass is statistically mediated by resting metabolic rate, suggesting that energy expenditure per se may influence energy intake. A recent MRI study has reported that fasting hunger was associated with high metabolic rate organ (heart, liver, brain, kidneys) and skeletal muscle mass. Integrating measures of body composition at the tissue-organ level and markers of their metabolic function with appetitive measures could provide novel insight into the mechanisms that influence appetite. SUMMARY: These recent findings suggest that fat-free mass and resting metabolic rate are determinants of energy intake. Consideration of fat-free mass and energy expenditure as physiological sources of appetitive signals helps reconcile the mechanisms underpinning the inhibition of eating with those that drive eating.

The complex pattern of the effects of prolonged frequent exercise on appetite control, and implications for obesity.

From a public health perspective, much of the interest in the relationship between exercise and appetite rests on the implications for energy balance and obesity. Energy balance reflects a dynamic 2-way interaction between energy expenditure (EE) and energy intake (EI). Physical activity and exercise, and appetite are the behavioural components of EE and EI, respectively. Beyond EE, exercise is a powerful and complex physiological stimulus acting on several bodily systems. There are multiple effects of frequent and prolonged exercise on appetite which include inter alia an increase in fasting hunger, an enhancement of post-prandial satiety, a modulation of the hedonic responses to food and improvements in eating behaviour traits. These lead to variable adjustments in EI and in a reduction in the susceptibility to overconsumption. Frequent and prolonged physical activity and exercise behaviour can strengthen and sensitise the appetite control system, whilst physical inactivity and sedentariness (low level of EE) fails to downregulate EI and can permit overconsumption. Not all of the effects of exercise operate uniformly to drive appetite in the same direction. The complexity of the interaction between EE and EI means that the effects of prolonged exercise are characterised by substantial individual heterogeneity. This leads to variable effects on energy balance and body mass.

Validation of a Mobile App-Based Visual Analog Scale for Appetite Measurement in the Real World: A Randomized Digital Clinical Trial.

There has been no validated digital tool for measuring appetite with a visual analog scale (VAS) through a mobile app using participants' smart phones for data collection in virtual settings. To fill the gap, we developed a digital VAS and conducted a digital cross-over clinical trial by comparing appetite responses measured by this digital tool versus paper-based VAS in 102 participants in a free-living environment. Participants consumed either a 230 or 460 kcal breakfast in randomized order in two virtual sessions, and their appetite was measured over the next 4 h using both tools. The results revealed no significant difference in hunger, fullness, satiety, or desire to eat measured by digital and paper VAS. Paper VAS resulted in a higher prospective consumption score than digital VAS; the difference (1.1 out of 100 points) was statistically significant but not practically relevant. Bland and Altman analysis also indicated consistency in the results from the two methods. In conclusion, digital VAS on a smart phone is a validated tool for appetite measurement in the real world; it provides a new way for researchers to leverage participants' mobile devices for appetite data collection in digital trials.

Fat-Free Mass and Total Daily Energy Expenditure Estimated Using Doubly Labeled Water Predict Energy Intake in a Large Sample of Community-Dwelling Older Adults.

BACKGROUND: Up to 30% of community-based older adults report reduced appetite and energy intake (EI), but previous research examining the underlying physiological mechanisms has focused on the mechanisms that suppress eating rather than the hunger drive and EI. OBJECTIVES: We examined the associations between fat-free mass (FFM), physical activity (PA), total daily energy expenditure (TDEE), and self-reported EI in older adults. METHODS: The present study was a secondary analysis of the Interactive Diet and Activity Tracking in AARP study. Body composition (deuterium dilution), PA (accelerometry), and TDEE (doubly labeled water) were measured in 590 older adults (age, 63.1 ± 5.9 years; BMI, 28.1 ± 4.9 kg/m2). The total daily EI was estimated from a single 24-hour dietary recall (EIsingle; ±1 month of PA and TDEE measurement) and the mean of up to 6 recalls over a 12-month period (EImean), with misreporters classified using the 95% CIs between the EImean and TDEE. RESULTS: After controlling for age and sex, linear regression demonstrated that FFM and TDEE predicted EI when estimated from a single 24-hour dietary recall (P < 0.05), from the mean of up to 6 dietary recalls (P < 0.05), and after the removal of those classified as underreporters (P < 0.001). Age moderated the associations between FFM and EIsingle (P < 0.001), FFM and EImean (P < 0.001), and TDEE with EIsingle (P = 0.016), with associations becoming weaker across age quintiles. CONCLUSIONS: These data suggest that the total daily EI is proportional to the FFM and TDEE, but not fat mass, in older adults. These associations may reflect an underling drive to eat that influences the daily food intake. While the associations between FFM or TDEE and EI existed across all age quintiles, these associations weakened with increasing age.

Fat-Free Mass and Total Daily Energy Expenditure Estimated Using Doubly Labeled Water Predict Energy Intake in a Large Sample of Community-Dwelling Older Adults.

BACKGROUND: Up to 30% of community-based older adults report reduced appetite and energy intake (EI), but previous research examining the underlying physiological mechanisms has focused on the mechanisms that suppress eating rather than the hunger drive and EI. OBJECTIVES: We examined the associations between fat-free mass (FFM), physical activity (PA), total daily energy expenditure (TDEE), and self-reported EI in older adults. METHODS: The present study was a secondary analysis of the Interactive Diet and Activity Tracking in AARP study. Body composition (deuterium dilution), PA (accelerometry), and TDEE (doubly labeled water) were measured in 590 older adults (age, 63.1 ± 5.9 years; BMI, 28.1 ± 4.9 kg/m2). The total daily EI was estimated from a single 24-hour dietary recall (EIsingle; ±1 month of PA and TDEE measurement) and the mean of up to 6 recalls over a 12-month period (EImean), with misreporters classified using the 95% CIs between the EImean and TDEE. RESULTS: After controlling for age and sex, linear regression demonstrated that FFM and TDEE predicted EI when estimated from a single 24-hour dietary recall (P < 0.05), from the mean of up to 6 dietary recalls (P < 0.05), and after the removal of those classified as underreporters (P < 0.001). Age moderated the associations between FFM and EIsingle (P < 0.001), FFM and EImean (P < 0.001), and TDEE with EIsingle (P = 0.016), with associations becoming weaker across age quintiles. CONCLUSIONS: These data suggest that the total daily EI is proportional to the FFM and TDEE, but not fat mass, in older adults. These associations may reflect an underling drive to eat that influences the daily food intake. While the associations between FFM or TDEE and EI existed across all age quintiles, these associations weakened with increasing age.

Effect of exercise training before and after bariatric surgery: A systematic review and meta-analysis.

We aimed to assess the effectiveness of exercise training programs in adults with severe obesity undergoing bariatric surgery. A systematic search of controlled trials published up to October 2019 that assigned participants to either a preoperative or postoperative exercise training group or a nonexercise group was performed. Meta-analyses were conducted using random-effects models. Twenty-two training programs were assessed (18 performed after bariatric surgery). The effect of preoperative exercise training on postsurgery outcomes was reported in only one study. Compared with the control condition without exercise, postoperative exercise training led to higher weight loss (N = 14, mean difference [95% CI] = -1.8 [-3.2; -0.4] kg, P = 0.01), fat loss (N = 9, P = 0.01), increase in VO2 max (N = 8, P < 0.0001), and increase in muscle strength (N = 9, P < 0.0001). No significant effect was found on lean body mass (N = 11). Preliminary evidence suggests a beneficial effect of postoperative exercise training on bone mineral density (N = 3, P < 0.001) and weight maintenance after the end of the intervention (N = 2, P < 0.001) but no significant effect on quality of life (N = 2), habitual physical activity (N = 2), or cardiometabolic outcomes (N < 4). In conclusion, exercise training performed after bariatric surgery improves physical fitness and leads to a small additional weight and fat loss and may prevent bone loss and weight regain after bariatric surgery.

Exercise training in the management of overweight and obesity in adults: Synthesis of the evidence and recommendations from the European Association for the Study of Obesity Physical Activity Working Group.

There is a need for updated practice recommendations on exercise in the management of overweight and obesity in adults. We summarize the evidence provided by a series of seven systematic literature reviews performed by a group of experts from across Europe. The following recommendations with highest strength (Grade A) were derived. For loss in body weight, total fat, visceral fat, intra-hepatic fat, and for improvement in blood pressure, an exercise training program based on aerobic exercise at moderate intensity is preferentially advised. Expected weight loss is however on average not more than 2 to 3 kg. For preservation of lean mass during weight loss, an exercise training program based on resistance training at moderate-to-high intensity is advised. For improvement in insulin sensitivity and for increasing cardiorespiratory fitness, any type of exercise training (aerobic, resistance, and combined aerobic or resistance) or high-intensity interval training (after thorough assessment of cardiovascular risk and under supervision) can be advised. For increasing muscular fitness, an exercise training program based preferentially on resistance training alone or combined with aerobic training is advised. Other recommendations deal with the beneficial effects of exercise training programs on energy intake and appetite control, bariatric surgery outcomes, and quality of life and psychological outcomes in management of overweight and obesity.

Effect of different types of regular exercise on physical fitness in adults with overweight or obesity: Systematic review and meta-analyses.

This systematic review examined the effect of exercise training interventions on physical fitness in adults with overweight or obesity and compared the effectiveness of different types of exercise training. Four electronic databases were searched. Articles were included if they described randomized controlled trials of exercise training interventions and their effect on maximal oxygen consumption or muscle strength in adults with overweight or obesity. Changes in outcome parameters were analyzed using random effects meta-analyses for different training types (aerobic, resistance, combined aerobic plus resistance, and high-intensity interval training). Eighty-eight articles satisfied the inclusion criteria of which 66 (3964 participants) could be included in the meta-analyses. All training types increased VO2max (mean difference 3.82 ml/min/kg (95% CI 3.17, 4.48), P < 0.00001; I2 = 48%). In direct comparisons, resistance training was less effective in improving VO2max than aerobic training, HIIT was slightly more effective than aerobic training, and no difference between aerobic and combined aerobic plus resistance training was found. For muscle strength benefits, incorporation of resistance exercise in the training program is indicated. Exercise training increases VO2max and muscle strength in adults with overweight or obesity. Differences between training types should be weighed with other needs and preferences when health professionals advise on exercise training to improve physical fitness.

Effect of exercise training on psychological outcomes in adults with overweight or obesity: A systematic review and meta-analysis.

This study systematically identified the effects of exercise on multiple psychological outcomes among adults with overweight/obesity, also assessing whether these effects differed across exercise types, genders, age, and body mass index (BMI) categories. Pubmed, Web of Science, PsychInfo, and SportDiscus were searched up to October 2019 for peer-reviewed papers assessing exercise training effects on psychosocial outcomes in adults with overweight/obesity. Thirty-six articles, 32 randomized controlled trials (RCTs), were included in this review. Most interventions were supervised (65%), ranging between 6 and 76 weeks (median = 12). Sixteen psychological outcomes were studied. Exercise induced positive changes in quality of life but did not reduce depression. Large effect sizes were observed on quality of life's physical component, but exercise was also able to improve vitality and mental health. Most psychological outcomes (e.g., body image, anxiety, and perceived stress) are poorly studied, evidencing either conflicting or null exercise effects. Exercise self-efficacy and autonomous motivations were also consistently improved. Exercise types and gender seem to moderate exercise psychological effects. Exercise training programs might lead to positive changes in some psychological outcomes, especially in quality of life, in adults with overweight and obesity, but more studies, with greater systematization in program characteristics, and longer follow-ups are still required to allow more solid conclusions.

Effect of exercise on cardiometabolic health of adults with overweight or obesity: Focus on blood pressure, insulin resistance, and intrahepatic fat-A systematic review and meta-analysis.

This systematic review examined the impact of exercise intervention programs on selected cardiometabolic health indicators in adults with overweight or obesity. Three electronic databases were explored for randomized controlled trials (RCTs) that included adults with overweight or obesity and provided exercise-training interventions. Effects on blood pressure, insulin resistance (homeostasis model of insulin resistance, HOMA-IR), and magnetic resonance measures of intrahepatic fat in exercise versus control groups were analyzed using random effects meta-analyses. Fifty-four articles matched inclusion criteria. Exercise training reduced systolic and diastolic blood pressure (mean difference, MD = -2.95 mmHg [95% CI -4.22, -1.68], p < 0.00001, I2  = 63% and MD = -1.93 mmHg [95% CI -2.73, -1.13], p < 0.00001, I2  = 54%, 60 and 58 study arms, respectively). Systolic and diastolic blood pressure decreased also when considering only subjects with hypertension. Exercise training significantly decreased HOMA-IR (standardized mean difference, SMD = -0.34 [-0.49, -0.18], p < 0.0001, I2 = 48%, 37 study arms), with higher effect size in subgroup of patients with type 2 diabetes (SMD = -0.50 [95% CI: -0.83, -0.17], p = 0.003, I2 = 39%). Intrahepatic fat decreased significantly after exercise interventions (SMD = -0.59 [95% CI: -0.78, -0.41], p < 0.00001, I2  = 0%), with a larger effect size after high-intensity interval training. In conclusion, exercise training is effective in improving cardiometabolic health in adults with overweight or obesity also when living with comorbitidies.

Effect of exercise training interventions on energy intake and appetite control in adults with overweight or obesity: A systematic review and meta-analysis.

This systematic review examined the impact of exercise training interventions on energy intake (EI) and appetite control in adults with overweight/obesity (≥18 years including older adults). Articles were searched up to October 2019. Changes in EI, fasting appetite sensations, and eating behavior traits were examined with random effects meta-analysis, and other outcomes were synthesized qualitatively. Forty-eight articles were included (median [range] BMI = 30.6 [27.0-38.4] kg/m2 ). Study quality was rated as poor, fair, and good in 39, seven, and two studies, respectively. Daily EI was assessed objectively (N = 4), by self-report (N = 22), with a combination of the two (N = 4) or calculated from doubly labeled water (N = 1). In studies rated fair/good, no significant changes in pre-post daily EI were found and a small but negligible (SMD < 0.20) postintervention difference when compared with no-exercise control groups was observed (five study arms; MD = 102 [1, 203] kcal). There were negligible-to-small pre-post increases in fasting hunger and dietary restraint, decrease in disinhibition, and some positive changes in satiety and food reward/preferences. Within the limitations imposed by the quality of the included studies, exercise training (median duration of 12 weeks) leads to a small increase in fasting hunger and a small change in average EI only in studies rated fair/good. Exercise training may also reduce the susceptibility to overconsumption (PROSPERO: CRD42019157823).

Effect of exercise training on weight loss, body composition changes, and weight maintenance in adults with overweight or obesity: An overview of 12 systematic reviews and 149 studies.

This overview of reviews aimed to summarize the effects of exercise training programs on weight loss, changes in body composition, and weight maintenance in adults with overweight or obesity. A systematic search of systematic reviews and meta-analyses (SR-MAs) published between 2010 and December 2019 was performed. Only SR-MAs of controlled trials were included. The mean difference (MD) or standardized MD (SMD) were extracted from SR-MAs. Twelve SR-MAs (149 studies) were included. Exercise led to a significant weight loss (4 SR-MAs, MDs ranging from -1.5 to -3.5 kg), fat loss (4 SR-MAs, MDs ranging from -1.3 to -2.6 kg) and visceral fat loss (3 SR-MAs, SMDs ranging from -0.33 to -0.56). No difference in weight, fat, and visceral loss was found between aerobic and high-intensity interval training as long as energy expenditure was equal. Resistance training reduced lean mass loss during weight loss (1 SR-MA, MD: 0.8 [95%CI: 0.4-1.3] kg). No significant effect of exercise was found on weight maintenance (1 SR-MA). These findings show favorable effects of exercise training on weight loss and body composition changes in adults with overweight or obesity. Visceral fat loss may lead to benefits for cardiometabolic health. More research is needed to identify training modalities that promote weight maintenance.

The "drive to eat" hypothesis: energy expenditure and fat-free mass but not adiposity are associated with milk intake and energy intake in 12 week infants.

BACKGROUND: Recent work has challenged the long-held assumption that appetite functions to maintain stable body mass and fat mass (FM), suggesting instead that appetite matches food intake to energy expenditure and its correlate, fat-free mass (FFM). Whether this scenario applies to young infants, in chronic positive energy balance, remains unknown. OBJECTIVES: To test associations of components of energy expenditure and body composition with milk intake (MI) and energy intake (EI) in 12-week infants, by reanalyzing published cross-sectional data. METHODS: Data were available for 48 infants. In addition to anthropometric measurements, we assessed MI and EI by test-weighing, sleeping metabolic rate (SMR) by indirect calorimetry, and FFM, FM, and total energy expenditure (TEE) by doubly labeled water. Mean parental height was calculated as a marker of infant growth drive. Correlation and multiple regression analyses were applied. RESULTS: MI and EI correlated with FFM (r = 0.47 and 0.57, respectively; P < 0.01), but not FM (P > 0.6). MI and EI correlated with SMR (r = 0.42 and 0.53, respectively; P < 0.01) and TEE (r = 0.50 and 0.49, respectively; P < 0.01). SMR and TEE correlated with FFM (r = 0.41 and 0.42, respectively; P < 0.01), but not FM (P > 0.2). In a multiple regression analysis, MI was independently associated with TEE (partial r = 0.39) and FFM (partial r = 0.35). EI showed similar associations. Mean parental height was correlated with weight gain, MI, and EI. CONCLUSIONS: As in adults, MI and EI in young infants were strongly associated with FFM and with total and sleeping components of energy expenditure, but not with fatness. The infant's growth drive contributed to these associations. This suggests that appetite is regulated by the rate of energy expenditure, the size of energy-using tissues, and tissue deposition rate, and that the high levels of body fat characteristic of infants may not constrain weight gain.

Circulating Metabolites Associated with Postprandial Satiety in Overweight/Obese Participants: The SATIN Study.

Scope: To identify a metabolomic profile related to postprandial satiety sensations involved in appetite control would help for a better understanding of the regulation of food intake. Methods and Results: A cross-sectional analysis of plasma metabolites was conducted over 151 overweight/obese adults from the "Satiety Innovation"-SATIN study, a randomized clinical trial of a 12-week weight-loss maintenance period. Postprandial satiety sensations (3 h-iAUC) were assessed by visual analogue scale (VAS) at the beginning and at the end of the study. Fasting plasma metabolites were profiled using a targeted multiplatform metabolomics approach before each appetite test meal. Associations between 124 metabolites and iAUC-satiety were assessed using elastic net linear regression analyses. The accuracy of the multimetabolite weighted models for iAUC-VAS was evaluated using a 10-fold cross-validation (CV) approach and the Pearson's correlation coefficients were estimated. Five and three metabolites were selected in the first and the second assessments, respectively. Circulating glycine and linoleic acid concentrations were consistently and positively associated with higher iAUC-satiety in both visits. Sucrose and sphingomyelins (C32:2, C38:1) were negatively associated with iAUC-satiety in the first visit. The Pearson correlations coefficients between the metabolomic profiles and iAUC-satiety in the first and the second appetite assessments were 0.37 and 0.27, respectively. Conclusion: Higher glycine and linoleic acid were moderately but consistently associated with higher postprandial satiety in two different appetite assessments in overweight and obese subjects.

Eating Behavior, Physical Activity and Exercise Training: A Randomized Controlled Trial in Young Healthy Adults.

Regular physical activity (PA) is an important part of the treatment of several medical conditions, including overweight and obesity, in which there may be a weakened appetite control. Eating behaviour traits influence weight control and may be different in active and sedentary subjects. This paper reports the relationships between the time spent in sedentary behaviour and physical activity (PA) of different intensity, and eating behaviour traits in young, healthy adults. Additionally, it reports the results of a six-month-long, randomized, controlled trial to examine the effect of an exercise intervention on eating behaviour traits. A total of 139 young (22.06 ± 2.26 years) healthy adults (68.35% women) with a Body Mass Index (BMI) of 24.95 ± 4.57 kg/m2 were enrolled. Baseline assessments of habitual PA were made using wrist-worn triaxial accelerometers; eating behaviour traits were examined via the self-reported questionnaires: Binge Eating, Three-Factor Eating Questionnaire-R18 and Control of Eating Questionnaire. The subjects were then randomly assigned to one of three groups: control (usual lifestyle), moderate-intensity exercise (aerobic and resistance training 3¨C4 days/week at a heart rate equivalent to 60% of the heart rate reserve (HRres) for the aerobic component, and at 50% of the 1 repetition maximum (RM) for the resistance component), or vigorous-intensity exercise (the same training but at 80% HRres for half of the aerobic training, and 70% RM for the resistance training). At baseline, sedentary behaviour was inversely associated with binge eating (r = -0.181, p < 0.05) and with uncontrolled eating (r = -0.286, p = 0.001). Moderate PA (MPA) was inversely associated with craving control (r = -0.188, p < 0.05). Moderate-to-vigorous PA (MVPA) was directly associated with binge eating (r = 0.302, p < 0.001) and uncontrolled eating (r = 0.346, p < 0.001), and inversely associated with craving control (r = -0.170, p < 0.015). Overall, PA was directly associated with binge eating (r = 0.275, p = 0.001), uncontrolled eating (r = 0.321, p < 0.001) and emotional eating (r = 0.204, p < 0.05). Additionally, only emotional eating was modified by the intervention, increasing in the vigorous-intensity exercise group (p < 0.05). In summary, we observed that time spent in sedentary behaviour/PA of different intensity is associated with eating behaviour traits, especially binge eating in young adults. In contrast, the six-month exercise intervention did not lead to appreciable changes in eating behaviour traits.

Validation of the Activity Preference Assessment: a tool for quantifying children's implicit preferences for sedentary and physical activities.

BACKGROUND: High levels of sedentary behavior and low physical activity are associated with poor health, and the cognitive determinants of these behaviors in children and adolescents are not well understood. To address this gap, we developed a novel, non-verbal, computer-based assessment to quantify the degree to which youth prefer to be sedentary relative to physically active in their leisure time. METHODS: The Activity Preference Assessment (APA) uses a forced-choice paradigm to understand implicit decision-making processes when presented with common sedentary and physical activities. The APA bias score ranges from - 100 to + 100, with positive scores indicating a relative preference for sedentary activities, and negative scores representing a preference for physical activities. In 60 children ages 8-17 years, we assessed the validity of this behavioral task against a free-choice play observation, accelerometry-measured activity, anthropometrics and body composition, and cardiorespiratory fitness. We explored neighborhood, family, and individual-level factors that may influence implicit activity preferences. Test-retest reliability was assessed over one week. RESULTS: The majority of children (67%) preferred sedentary relative to physical activities. APA bias scores were positively associated with sedentary time during free-choice play. In girls, bias scores were negatively associated with average daily MVPA. APA bias scores were positively associated with body fat and negatively associated with cardiorespiratory fitness. These findings were independent of age, sex, and race/ethnicity. Neighborhood access to physical activity spaces, the number of people in the home, perceived physical self-competence (e.g., coordination, strength), and self-reported depressive symptoms were associated with activity preferences. The intra-class correlation for test-retest reliability was r = 0.59. CONCLUSIONS: The APA shows promise as a novel tool for quantifying children's relative preference for sedentary versus physical activities. Implicit bias scores from the APA are clinically meaningful, as shown by significant associations with adiposity and cardiorespiratory fitness. Future longitudinal studies should examine the directionality of the association between preferences and health markers, and the degree to which implicit activity preferences are modifiable. Importantly, the task only takes an average of 10 min to complete, highlighting a potential role as an efficient screening tool for the propensity to be sedentary versus physically active. TRIAL REGISTRATION: ClinicalTrials.gov NCT03624582 .

The Effect of Exercise Training on Total Daily Energy Expenditure and Body Composition in Weight-Stable Adults: A Randomized, Controlled Trial.

BACKGROUND: The present study examined, among weight-stable overweight or obese adults, the effect of increasing doses of exercise energy expenditure (EEex) on changes in total daily energy expenditure (TDEE), total body energy stores, and body composition. METHODS: Healthy, sedentary overweight/obese young adults were randomized to one of 3 groups for a period of 26 weeks: moderate-exercise (EEex goal of 17.5 kcal/kg/wk), high-exercise (EEex goal of 35 kcal/kg/wk), or observation group. Individuals maintained body weight within 3% of baseline. Pre/postphysical activity between-group measurements included body composition, calculated energy intake, TDEE, energy stores, and resting metabolic rate. RESULTS: Sixty weight-stable individuals completed the protocols. Exercise groups increased EEex in a stepwise manner compared with the observation group (P < .001). There was no group effect on changes in TDEE, energy intake, fat-free mass, or resting metabolic rate. Fat mass and energy stores decreased among the females in the high-exercise group (P = .007). CONCLUSIONS: The increase in EEex did not result in an equivalent increase in TDEE. There was a sex difference in the relationship among energy balance components. These results suggest a weight-independent compensatory response to exercise training with potentially a sex-specific adjustment in body composition.

The drive to eat in homo sapiens: Energy expenditure drives energy intake.

The drive to eat is a component of appetite control, independent of the omnivorous habit of humans, and separate from food choice, satiety and food reward. The drive forms part of the tonic component of appetite and arises from biological needs; it is distinct from episodic aspects of appetite which are heavily influenced by culture and the environment (and which reflect the omnivorous habit). It is proposed that the tonic drive to eat reflects a need state generated by metabolic energy expenditure (EE) required to maintain the functioning and integrity of vital organs. Specifically, the tonic drive is quantitatively associated with fat-free mass (FFM) and resting metabolic rate (RMR). A rational proposition is that high metabolic rate organs (such as heart, liver, kidneys, brain) together with skeletal muscle generate a metabolic need which drives energy intake (EI). The basic phenomenon of a relationship between FFM, RMR and EI, first published in 2011, has been substantially replicated and there are at least 14 concordant published studies carried out in 9 different countries (and 4 continents) with various ethnic groups of lean and obese humans. These studies demonstrate that FFM and RMR represent major determinants of the drive to eat, and this is rational from an evolutionary perspective. The EE of bodily movements through skeletal muscle activity (namely physical activity and exercise) represents another driver which is clearly but more weakly associated with an increase in EI. This account of appetite control, developed within an energy balance framework, is consistent with the apparent inexorable escalation of fatness in individual humans, and for the progressive increase in the prevalence of obesity which, among other factors, reflects the difficulty of managing the biological drive to eat.

Brown adipose tissue volume and 18F-fluorodeoxyglucose uptake are not associated with energy intake in young human adults.

BACKGROUND: Several studies have explored the role of human brown adipose tissue (BAT) in energy expenditure. However, the link between BAT and appetite regulation needs to be more rigorously examined. OBJECTIVES: We aimed to investigate the associations of BAT volume and 18F-fluordeoxyglucose (18F-FDG) uptake after a personalized cold exposure with energy intake and appetite-related sensations in young healthy humans. METHODS: A total of 102 young adults (65 women; age: 22.08 ± 2.17 y; BMI: 25.05 ± 4.93 kg/m 2) took part in this cross-sectional study. BAT volume, BAT 18F-FDG uptake, and skeletal muscle 18F-FDG uptake were assessed by means of static 18F-FDG positron-emission tomography and computed tomography scans after a 2-h personalized exposure to cold. Energy intake was estimated via an objectively measured ad libitum meal and three nonconsecutive 24-h dietary recalls. Appetite-related sensations (i.e., hunger and fullness) were recorded by visual analog scales before and after a standardized breakfast (energy content = 50% of basal metabolic rate) and the ad libitum meal. Body composition was assessed by a whole-body DXA scan. RESULTS: BAT volume and 18F-FDG uptake were not associated with quantified ad libitum energy intake (all P > 0.088), nor with habitual energy intake estimated from the 24-h dietary recalls (all P  > 0.683). Lean mass was positively associated with both the energy intake from the ad libitum meal (ß: 17.612, R2 = 0.213; P < 0.001) and the habitual energy intake (ß: 16.052, R2 = 0.123; P = 0.001). Neither the interaction BAT volume × time elapsed after meal consumption nor that of BAT 18F-FDG uptake × time elapsed after meal consumption had any significant influence on appetite-related sensations after breakfast or after meal consumption (all P > 0.3). CONCLUSIONS: Neither BAT volume, nor BAT 18F-FDG uptake after cold stimulation, are related to appetite regulation in young adults. These results suggest BAT plays no important role in the regulation of energy intake in humans.This trial was registered at clinicaltrials.gov as NCT02365129.