Acute and long-term effects of exercise on appetite control: is there any benefit for weight control?

Does eating less or exercising more to reduce energy availability produce distinct metabolic responses?

When less energy is available to consume, people often lose weight, which reduces their overall metabolic rate. Their cellular metabolic rate may also decrease (metabolic adaptation), possibly reflected in physiological and/or endocrinological changes. Reduced energy availability can result from calorie restriction or increased activity energy expenditure, raising the following question that our review explores: do the body's metabolic and physiological responses to this reduction differ or not depending on whether they are induced by dietary restriction or increased activity? First, human studies offer indirect, contentious evidence that the body metabolically adapts to reduced energy availability, both in response to either a calorie intake deficit or increased activity (exercise; without a concomitant increase in food intake). Considering individual aspects of the body's physiology as constituents of whole-body metabolic rate, similar responses to reduced energy availability are observed in terms of reproductive capacity, somatic maintenance and hormone levels. By contrast, tissue phenotypic responses differ, most evidently for skeletal tissue, which is preserved in response to exercise but not calorie restriction. Thus, while in many ways 'a calorie deficit is a calorie deficit', certain tissues respond differently depending on the energy deficit intervention. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part I)'.

Exergaming During Ramadan Intermittent Fasting Improve Body Composition as Well as Physiological and Psychological Responses to Physical Exercise in Adolescents With Obesity

The effects of exergaming on biochemical responses has been investigated; however, no data is available for this effect during Ramadan intermittent fasting (RIF). RIF is a daily fasting characterized by abstaining from eating and drinking from sunrise to sunset for 29-30 days. The purpose of this study was to investigate the effect of exergaming during RIF on body composition, physical performance and hematological parameters in overweight and adolescents with obesity. Twenty-four adolescents with obesity were divided into two groups [control group (CG), n = 12, or cooperative sport exergaming group (EG), n = 12: 45 min per session during five days per week)]. Participants completed a 6-min walking test (6MWT), a squat jump test and a 10 and a 30m sprint tests in four different occasions: before Ramadan (T0), the second week of Ramadan (T1), the fourth week of Ramadan (T2), and after Ramadan (T3). Blood pressure, rating of perceived exertion (RPE), body composition, central obesity index, dietary intake and profile of mood states (POMS) were, also, assessed over the four periods. The results showed that body weight, body mass index and body fat percentage were significantly lower at T2 compared to T0 and T1 in the EG. After RIF, body composition returned to the values recorded before RIF. The POMS score was significantly lower during T2 compared to T0, T1 and T3 in the EG. The vertical jump and the 6MWT distance were significantly higher (i) at T2 compared to T0, T1 and T3 in the EG and (ii) in EG compared to CG at T2. RPE was significantly lower (i) at T2 compared to T0, T1 and T3 in the EG and (ii) in EG compared to CG at T2. Blood pressure was lower during T2 compared to the other periods in EG. The EG experienced significant decreases in total cholesterol and triglycerides during T2. However, no significant changes between groups and periods was reported for all the other parameters. In conclusion, exergaming during RIF has a positive effect on body composition and physiological and psychological responses in adolescents with obesity.

Planned morning aerobic exercise in a fasted state increases energy intake in the preceding 24 h

Purpose

We previously observed increased energy intake (EI) at the meal before planned afternoon exercise, but the proximity of the meal to exercise might have reduced the scale of the pre-exercise anticipatory eating. Therefore, this study examined EI in the 24 h before fasted morning exercise.

Methods

Fourteen males, experienced with gym-based aerobic exercise (age 25 ± 5 years, BMI 23.8 ± 2.5 kg/m²), completed counterbalanced exercise (EX) and resting (REST) trials. On day 1, subjects were told the following morning’s activity (EX/REST), before eating ad-libitum laboratory-based breakfast and lunch meals and a home-based afternoon/evening food pack. The following morning, subjects completed 30-min cycling and 30-min running (EX; 3274 ± 278 kJ) or 60-min supine rest (REST; 311 ± 34 kJ) fasted. Appetite was measured periodically, and EI quantified.

Results

Afternoon/evening EI (EX 7371 ± 2176 kJ; REST 6437 ± 2070 kJ; P = 0.017) and total 24-h EI (EX 14,055 ± 3672 kJ; REST 12,718 ± 3379 kJ; P = 0.011) were greater during EX, with no difference between trials at breakfast (P = 0.761) or lunch (P = 0.071). Relative EI (EI minus energy expended through EX/REST) was lower in EX (EX 10,781 ± 3539 kJ; REST 12,407 ± 3385 kJ; P = 0.004).

Conclusion

This study suggests planned fasted aerobic exercise increases EI during the preceding afternoon/evening, precipitating a ~ 10% increase in EI in the preceding 24-h. However, this increase did not fully compensate for energy expended during exercise; meaning exercise induced an acute negative energy balance.

Consumption of a High-Protein Meal Replacement Leads to Higher Fat Oxidation, Suppression of Hunger, and Improved Metabolic Profile After an Exercise Session

The aim of this study was to compare the impact of a high-protein meal replacement (HP-MR) versus a control (CON) breakfast on exercise metabolism. In this acute, randomized controlled, cross-over study, participants were allocated into two isocaloric arms: (a) HP-MR: 30% carbohydrate, 43% protein, and 27% fat; (b) CON: 55% carbohydrate, 15% protein, and 30% fat. Following breakfast, participants performed a moderate-intensity aerobic exercise while inside a whole-body calorimetry unit. Energy expenditure, macronutrient oxidation, appetite sensations, and metabolic blood markers were assessed. Forty-three healthy, normal-weight adults (24 males) participated. Compared to the CON breakfast, the HP-MR produced higher fat oxidation (1.07 ± 0.33 g/session; p = 0.003) and lower carbohydrate oxidation (-2.32 ± 0.98 g/session; p = 0.023) and respiratory exchange ratio (-0.01 ± 0.00; p = 0.003) during exercise. After exercise, increases in hunger were lower during the HP-MR condition. Changes in blood markers from the fasting state to post-exercise during the HP-MR condition were greater for insulin, peptide tyrosine-tyrosine, and glucagon-like peptide 1, and lower for low-density lipoprotein cholesterol, triglyceride, and glycerol. Our primary findings were that an HP-MR produced higher fat oxidation during the exercise session, suppression of hunger, and improved metabolic profile after it.

Impact of different exercise training modalities on energy and nutrient intake and food consumption in sedentary middle-aged adults: a randomised controlled trial

BACKGROUND

Exercise could influence energy and macronutrient intake, which could have an important role on body composition changes in response to exercise. The present study aimed to investigate the effects of different training modalities in energy and macronutrient intake, and whether changes in energy and macronutrient intake influences changes in body composition in response to different training modalities.

METHODS

A 12-week randomised controlled trial was conducted. Eighty middle-aged sedentary adults were randomised to: (i) a control group; (ii) physical activity recommendation from the World Health Organization; (iii) high-intensity interval training; and (iv) whole-body electromyostimulation training. Dietary intake was assessed using the average of three 24-h recalls.

RESULTS

High-intensity interval training and whole-body electromyostimulation training groups showed lower fibre intake and higher dietary energy density. Our results showed a negative association was found between changes in energy intake and changes in lean mass index. No association was found between changes in protein intake and changes in lean mass index.

CONCLUSIONS

In conclusion, we observed a higher dietary energy density and lower fibre intake in high-intensity training groups.

User-documented food consumption data from publicly available apps: an analysis of opportunities and challenges for nutrition research

BACKGROUND

The need for a better understanding of food consumption behaviour within its behavioural context has sparked the interest of nutrition researchers for user-documented food consumption data collected outside the research context using publicly available nutrition apps. The study aims to characterize the scientific, technical, legal and ethical features of this data in order to identify the opportunities and challenges associated with using this data for nutrition research.

METHOD

A search for apps collecting food consumption data was conducted in October 2016 against UK Google Play and iTunes storefronts. 176 apps were selected based on user ratings and English language support. Publicly available information from the app stores and app-related websites was investigated and relevant data extracted and summarized. Our focus was on characteristics related to scientific relevance, data management and legal and ethical governance of user-documented food consumption data.

RESULTS

Food diaries are the most common form of data collection, allowing for multiple inputs including generic food items, packaged products, or images. Standards and procedures for compiling food databases used for estimating energy and nutrient intakes remain largely undisclosed. Food consumption data is interlinked with various types of contextual data related to behavioural motivation, physical activity, health, and fitness. While exchange of data between apps is common practise, the majority of apps lack technical documentation regarding data export. There is a similar lack of documentation regarding the implemented terms of use and privacy policies. While users are usually the owners of their data, vendors are granted irrevocable and royalty free licenses to commercially exploit the data.

CONCLUSION

Due to its magnitude, diversity, and interconnectedness, user-documented food consumption data offers promising opportunities for a better understanding of habitual food consumption behaviour and its determinants. Non-standardized or non-documented food data compilation procedures, data exchange protocols and formats, terms of use and privacy statements, however, limit possibilities to integrate, process and share user-documented food consumption data. An ongoing research effort is required, to keep pace with the technical advancements of food consumption apps, their evolving data networks and the legal and ethical regulations related to protecting app users and their personal data.

An acute bout of cycling does not induce compensatory responses in pre-menopausal women not using hormonal contraceptives

There is a clear need to improve understanding of the effects of physical activity and exercise on appetite control. Therefore, the acute and short-term effects (three days) of a single bout of cycling on energy intake and energy expenditure were examined in women not using hormonal contraceptives. Sixteen active (n = 8) and inactive (n = 8) healthy pre-menopausal women completed a randomised crossover design study with two conditions (exercise and control). The exercise day involved cycling for 1 h (50% of maximum oxygen uptake) and resting for 2 h, whilst the control day comprised 3 h of rest. On each experimental day participants arrived at the laboratory fasted, consumed a standardised breakfast and an ad libitum pasta lunch. Food diaries and combined heart rate-accelerometer monitors were used to assess free-living food intake and energy expenditure, respectively, over the subsequent three days. There were no main effects or condition (exercise vs control) by group (active vs inactive) interaction for absolute energy intake (P > 0.05) at the ad libitum laboratory lunch meal, but there was a condition effect for relative energy intake (P = 0.004, η_p² = 0.46) that was lower in the exercise condition (1417 ± 926 kJ vs. 2120 ± 923 kJ). Furthermore, post-breakfast satiety was higher in the active than in the inactive group (P = 0.005, η_p² = 0.44). There were no main effects or interactions (P > 0.05) for mean daily energy intake, but both active and inactive groups consumed less energy from protein (14 ± 3% vs. 16 ± 4%, P = 0.016, η_p² = 0.37) and more from carbohydrate (53 ± 5% vs. 49 ± 7%, P = 0.031, η_p² = 0.31) following the exercise condition. This study suggests that an acute bout of cycling does not induce compensatory responses in active and inactive women not using hormonal contraceptives, while the stronger satiety response to the standardised breakfast meal in active individuals adds to the growing literature that physical activity helps improve the sensitivity of short-term appetite control.

Predicting Change in Physical Activity: a Longitudinal Investigation Among Weight-Concerned College Women

BACKGROUND

Engaging in regular physical activity (PA) is critical for health, and adopting a consistent PA routine early in life is associated with greater PA over the lifespan. College women with weight concerns are at risk for weight gain, which may be prevented with regular PA. However, little is known about changes in PA engagement in this at-risk group.

PURPOSE

Using an outcome expectancy framework, this study used a prospective longitudinal design to examine changes in PA during the first 2 years of college. We tested for concurrent and prospective within-person relations between body satisfaction/perceived eating behavior and PA to determine when weight-concerned college women may increase or decrease PA.

METHODS

Women who reported weight concerns at the start of college (n = 294) completed five assessments over 2 years, including measured weight, body/eating experiences, and 4 days of pedometer steps (per assessment). Multilevel models addressed the resulting nested data structure (days within assessments within participants).

RESULTS

Over 2 years, within-person change accounted for 65 % of PA variability (ICC = 0.35). PA was greatest at (and subsequent to) times when body satisfaction was lower, and when disinhibited eating and hedonic hunger were higher, than an individual's average (ps < 0.05). These changes were associated with 1-3 % of the recommended daily step totals.

CONCLUSIONS

Weight-conscious college women show greater PA after negative eating and weight experiences. As these experiences change over time, health promotion efforts should help college women identify alternative, positive motivators for PA, which could facilitate consistent PA engagement.

Benefits of different intensity of aerobic exercise in modulating body composition among obese young adults: a pilot randomized controlled trial

BACKGROUND

The aim of present study was to compare the effects of different aerobic exercise intensities and energy expenditures on the body composition of sedentary obese college students in Taiwan.

METHODS

Forty-eight obese participants [body mass index (BMI) ≥ 27 kg/m², age 18-26 years] were randomized into four equal groups (n = 12): light-intensity training group (LITG), 40%-50% heart rate reserve (HRR); middle-intensity training group (MITG), 50%-70% HRR; high-intensity training group (HITG), 70%-80% HRR; and control group (CG). The aerobic exercise training program was conducted for 60 min per day on a treadmill 3 days per week for 12 weeks. All participant anthropometric data, blood biochemical parameters, and health-related physical fitness components were measured at baseline and after 12 weeks.

RESULTS

At baseline, the anthropometric indices did not differ significantly among the four groups (p > 0.05). After 12-week exercise intervention, the HITG and MITG had significantly more changes in body weight, waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR) than the LITG. The changes in BMI and body fat percentage differed among all four groups (p < 0.05).

CONCLUSIONS

A 12-week high-intensity exercise intervention with high energy expenditure can considerably reduce body weight, body fat, WC, WHR, and WHtR, whereas a light-intensity exercise intervention can significantly reduce body weight and body fat.

TRIAL REGISTRATION

Current Controlled Trials TPECTR09831410900 , registered on 24^th Dec 2009.

Energy balance, body composition, sedentariness and appetite regulation: pathways to obesity

Energy balance is not a simple algebraic sum of energy expenditure and energy intake as often depicted in communications. Energy balance is a dynamic process and there exist reciprocal effects between food intake and energy expenditure. An important distinction is that of metabolic and behavioural components of energy expenditure. These components not only contribute to the energy budget directly, but also by influencing the energy intake side of the equation. It has recently been demonstrated that resting metabolic rate (RMR) is a potential driver of energy intake, and evidence is accumulating on the influence of physical activity (behavioural energy expenditure) on mechanisms of satiety and appetite control. These effects are associated with changes in leptin and insulin sensitivity, and in the plasma levels of gastrointestinal (GI) peptides such as glucagon-like peptide-1 (GLP-1), ghrelin and cholecystokinin (CCK). The influence of fat-free mass on energy expenditure and as a driver of energy intake directs attention to molecules emanating from skeletal tissue as potential appetite signals. Sedentariness (physical inactivity) is positively associated with adiposity and is proposed to be a source of overconsumption and appetite dysregulation. The molecular signals underlying these effects are not known but represent a target for research.

Biological control of appetite: A daunting complexity

OBJECTIVE

This review summarizes a portion of the discussions of an NIH Workshop (Bethesda, MD, 2015) titled "Self-Regulation of Appetite-It's Complicated," which focused on the biological aspects of appetite regulation.

METHODS

This review summarizes the key biological inputs of appetite regulation and their implications for body weight regulation.

RESULTS

These discussions offer an update of the long-held, rigid perspective of an "adipocentric" biological control, taking a broader view that also includes important inputs from the digestive tract, from lean mass, and from the chemical sensory systems underlying taste and smell. It is only beginning to be understood how these biological systems are integrated and how this integrated input influences appetite and food eating behaviors. The relevance of these biological inputs was discussed primarily in the context of obesity and the problem of weight regain, touching on topics related to the biological predisposition for obesity and the impact that obesity treatments (dieting, exercise, bariatric surgery, etc.) might have on appetite and weight loss maintenance. Finally considered is a common theme that pervaded the workshop discussions, which was individual variability.

CONCLUSIONS

It is this individual variability in the predisposition for obesity and in the biological response to weight loss that makes the biological component of appetite regulation so complicated. When this individual biological variability is placed in the context of the diverse environmental and behavioral pressures that also influence food eating behaviors, it is easy to appreciate the daunting complexities that arise with the self-regulation of appetite.

Obesity treatment by very low-calorie-ketogenic diet at two years: reduction in visceral fat and on the burden of disease

The long-term effect of therapeutic diets in obesity treatment is a challenge at present. The current study aimed to evaluate the long-term effect of a very low-calorie-ketogenic (VLCK) diet on excess adiposity. Especial focus was set on visceral fat mass, and the impact on the individual burden of disease. A group of obese patients (n = 45) were randomly allocated in two groups: either the very low-calorie-ketogenic diet group (n = 22), or a standard low-calorie diet group; (n = 23). Both groups received external support. Adiposity parameters and the cumulative number of months of successful weight loss (5 or 10 %) over a 24-month period were quantified. The very low-calorie-ketogenic diet induced less than 2 months of mild ketosis and significant effects on body weight at 6, 12, and 24 months. At 24 months, a trend to regress to baseline levels was observed; however, the very low-calorie-ketogenic diet induced a greater reduction in body weight (-12.5 kg), waist circumference (-11.6 cm), and body fat mass (-8.8 kg) than the low-calorie diet (-4.4 kg, -4.1 cm, and -3.8 kg, respectively; p < 0.001). Interestingly, a selective reduction in visceral fat measured by a specific software of dual-energy x-ray absorptiometry (DEXA)-scan (-600 g vs. -202 g; p < 0.001) was observed. Moreover, the very low-calorie-ketogenic diet group experienced a reduction in the individual burden of obesity because reduction in disease duration. Very low-calorie-ketogenic diet patients were 500 months with 5 % weight lost vs. the low-calorie diet group (350 months; p < 0.001). In conclusion, a very low-calorie-ketogenic diet was effective 24 months later, with a decrease in visceral adipose tissue and a reduction in the individual burden of disease.

Obesity and energy balance: What is the role of physical activity?

Despite billions of dollars spent over decades of research, debate remains over the causes and solutions of the obesity epidemic. The specific role of physical activity in the prevention or treatment of obesity seems a particularly contentious issue, with opposing views put forth in both academic and popular media. In an attempt to provide context and clarity to the specific question of the role of physical activity in determination of body weight, we have attempted to identify evidence or lack thereof in the scientific literature and provide a summary of our findings. Areas covered: Topics included in this narrative review are an overview of energy balance, the relationship between physical activity and energy expenditure, compensatory responses in non-exercise energy expenditure and energy intake, and the relationship between physical activity and obesity. Expert commentary: Based on a review of the existing literature, daily physical activity and structured exercise has beneficial effects on an individual's body weight. In most instances, exercise occurring in adequate amounts will increase total daily energy expenditure and create an acute energy deficit, without compensatory decreases in non-exercise physical activity or energy expenditure nor compensatory increases in energy intake. Several gaps in the literature exist, both in terms of the number of adequately powered clinical trials with rigorous assessments of both energy intake and expenditure, and with a variety of study populations (by age, sex, race, etc.) and with varying exercise volumes and intensities.

Impact of imposed exercise on energy intake in children at risk for overweight

Background

Exercise not only has a direct effect on energy balance through energy expenditure (EE), but also has an indirect effect through its impact on energy intake (EI). This study examined the effects of acute exercise on daily ad libitum EI in children at risk for becoming overweight due to family history.

Methods

Twenty healthy-weight children (ages 9–12 years, 12 male/8 female) with at least one overweight biological parent (body mass index ≥ 25 kg/m²) participated. Children reported to the laboratory for one baseline and two experimental visits (EX = exercise, SED = sedentary) each separated by 1 week in a randomized crossover design. Two hours into the EX day session, children exercised at 70 % estimated VO_2max for 30 min on a cycle ergometer. Objective EI (kcal) was measured at a standard breakfast (~285 kcal) and ad libitum lunch, snack and dinner. Meals were identical on the EX and SED days. Activity-related EE (kcal) was estimated with accelerometers worn on the non-dominant wrist and ankle. Relative EI (kcal) was computed as the difference between Total EI and Activity-related EE for each testing day. Paired t-tests were performed to test differences in Total EI, Activity-related EE and Relative EI between the EX and SED days.

Results

Across all meals, Total EI was not statistically different between the EX and SED days (t = 1.8, p = 0.09). Activity-related EE was greater on the EX day compared to the SED day (t = 10.1, p < 0.001). By design, this difference was predominantly driven by activity during the morning (t = 20.4, p < 0.001). Because children consumed a similar number of kcal on each day, but had greater Activity-related EE on the EX day, Relative EI was lower (t = −5.15, p < 0.001) for the EX day (1636 ± 456 kcal) relative to the SED day (1862 ± 426 kcal).

Conclusions

Imposed exercise was effective in reducing Relative EI compared to being sedentary. Morning exercise may help children at risk for becoming overweight to better regulate their energy balance within the course of a day.

Objectively measured physical activity predicts subsequent energy intake in 300 women

OBJECTIVE

To determine if 7 d physical activity (PA) predicts energy intake over the same days and if PA on a given day predicts energy intake on the same day, the next day or subsequent days.

DESIGN

A 7 d prospective investigation. PA was measured using accelerometers worn for seven consecutive days. During the same week, total energy intake (including alcohol) was assessed using weighed food records.

SETTING

Twenty cities in the USA.

SUBJECTS

Three hundred middle-aged women.

RESULTS

After controlling for the covariates, energy intake was 36 (se 8) kJ higher for each additional 100000 activity counts (F=19·0, P<0·0001), based on the entire week of monitoring. Women with Low PA (n 75) had a mean energy intake of 8364 (sd 1235) kJ/d (1998 (sd 295) kcal/d), those with Moderate PA (n 150) consumed 8523 (sd 1264) kJ/d (2036 (sd 302) kcal/d) and those with High PA (n 75) consumed 9079 (sd 1473) kJ/d (2169 (sd 352) kcal/d; F=6·4, P=0·0019), a 5023 kJ/d (1200 kcal/d) difference between the High and Low PA groups. PA on a given day was predictive of energy consumption on the same day on four of the seven monitored days, and was predictive of energy intake the next day, with five of six associations significant. PA was not consistently predictive of energy intake on days beyond the next day.

CONCLUSIONS

Over 7 d, PA and energy consumption tend to be positively related. Considered day to day, increased PA is weakly associated with increased energy intake the following day and, to a lesser extent, the same day. Therefore, managing weight by increasing PA may not result in the energy deficit expected.

Diet Versus Exercise in Weight Loss and Maintenance: Focus on Tryptophan

An association between mood disturbance, the inability to lose or to stop gaining weight, and a craving for carbohydrates is manifested by many people who are overweight or are becoming so. In a recent study, we observed that low-calorie weight loss diet lowered not only levels of leptin but also levels of essential amino acid tryptophan (TRP) significantly. The disturbed metabolism of TRP might affect biosynthesis of serotonin and could thereby increase the susceptibility for mood disturbances and carbohydrate craving, increasing the cessation probability of weight reduction programs. Alternatively, moderate physical exercise – a potent stimulus to modulate (reduce/normalize) proinflammatory cytokines, which may affect TRP levels – could be helpful in improving mood status and preventing uncontrolled weight gain. In contrast, excessive physical exercise may induce breakdown of TRP when proinflammatory cascades together with TRP-degrading enzyme indoleamine 2,3-dioxygenase-1 are stimulated, which may lead to neuropsychiatric symptoms such as fatigue and low mood.

Exercise-related changes in between-network connectivity in overweight/obese adults

Understanding how exercise affects communication across the brain in overweight/obese individuals may provide insight into mechanisms of weight loss and maintenance. In the current study, we examined the effects of a 6-month exercise program in 11 overweight/obese individuals (mean BMI: 33.6±1.4mg/kg(2); mean age: 38.2±3.2years) on integrative brain "hubs," which are areas with high levels of connectivity to multiple large-scale networks thought to play an important role in multimodal integration among brain regions. These integrative hubs were identified with a recently developed between-network connectivity (BNC) metric, using functional magnetic resonance imaging (fMRI). BNC utilizes a multiple regression analysis approach to assess relationships between the time series of large-scale functionally-connected brain networks (identified using independent components analysis) and the time series of each individual voxel in the brain. This approach identifies brain regions with high between-network interaction, i.e., areas with high levels of connectivity to many large-scale networks. Changes in BNC following exercise were determined using paired t-tests, with results considered significant at a whole-brain level if they exceeded a voxel-wise threshold of p<0.01 and cluster-level family-wise error (FWE) correction for multiple comparisons of p<0.05. Following the intervention, BNC in the posterior cingulate cortex (PCC) was significantly reduced (p<0.001). The changes driving the observed effects were explored using Granger causality, finding significant reductions in both outgoing causal flow from the PCC to a number of networks (p<0.05; language network, visual network, sensorimotor network, left executive control network, basal ganglia network, posterior default mode network), in addition to reductions in ingoing causal flow to the PCC from a number of networks (p<0.05; ventral default mode network, language network, sensorimotor network, basal ganglia network). Change in BNC was related to changes in aerobic fitness level (VO2 max; p=0.008) and perceived hunger (Three Factor Eating Questionnaire; p=0.040). Overall, the impact of exercise on communication between large-scale networks may contribute to individual responsivity to exercise.

Acute exercise and gastric emptying: a meta-analysis and implications for appetite control

BACKGROUND

Gastric emptying (GE) could influence exercise-induced changes in appetite and energy intake. GE also could contribute to changes in gastric symptoms and the availability of nutrients during exercise, which will subsequently affect performance.

OBJECTIVE

The objective of this review was to determine the effects of acute exercise on GE using a systematic review and meta-analysis. The most common parameters to determine GE were selected, consisting of half-emptying time and volume emptied. Oral-caecal transit time (OCTT) was also examined.

DATA SOURCES

Research databases (PubMed, Scopus, Google Scholar, EBSCOhost, SPORTDiscus) were searched through November 2013 for original studies, abstracts, theses and dissertations that examined the influence of acute exercise on GE.

STUDY SELECTION

Studies were included if they evaluated GE or OCTT during and/or after exercise and involved a resting control trial.

STUDY APPRAISAL AND SYNTHESIS

Initially, 195 studies were identified. After evaluation of study characteristics and quality and validity, data from 20 studies (35 trials) involving 221 participants (157 men; 52 women; 12 unknown) were extracted for meta-analysis. Random-effects meta-analyses were utilised for the three main outcome variables, and effect sizes (ES) are reported as Hedge's g due to numerous small sample sizes.

RESULTS

Random-effects modelling revealed non-significant and small/null main effect sizes for volume emptied (ES = 0.195; 95% CI -0.25 to 0.64), half-time (ES = -0.109, 95% CI -0.66 to 0.44) and OCTT (ES = 0.089; 95% CI -0.64 to 0.82). All analyses exhibited significant heterogeneity and numerous variables moderated the results. There was a dose response of exercise intensity; at lower intensities GE was faster, and at high exercise intensities GE was slower. Walking was associated with faster GE and cycling with slower GE. Greater volume of meal/fluid ingested, higher osmolality of beverage and longer exercise duration were also associated with slower GE with exercise.

LIMITATIONS

The major limitation is that the majority of studies utilised a liquid bolus administered pre-exercise to determine GE; the relationship to post-exercise appetite and energy intake remains unknown. Study populations were also generally active or trained individuals. Furthermore, our review was limited to English language studies and studies that utilised resting control conditions.

CONCLUSIONS

These results suggest that exercise intensity, mode, duration and the nature of meal/fluid ingested all influence GE during and after acute exercise. The relationship of GE parameters with appetite regulation after exercise remains largely unexplored. Further integrative studies combining GE and alterations in gut hormones, as well as in populations such as overweight and obese individuals are needed.

Reciprocal Compensation to Changes in Dietary Intake and Energy Expenditure within the Concept of Energy Balance

An imbalance between energy intake and energy expenditure is the primary etiology for excess weight gain. Increased energy expenditure via exercise and energy restriction via diet are commonly used approaches to induce weight loss. Such behavioral interventions, however, have generally resulted in a smaller than expected weight loss, which in part has been attributed to compensatory adaptations in other components contributing to energy balance. Current research points to a loose coupling between energy intake and energy expenditure on a daily basis, and evidence for long-term adaptations has been inconsistent. The lack of conclusive evidence on compensatory adaptations in response to alterations in energy balance can be attributed to differences in intervention type and study population. Physical activity (PA) levels may be reduced in response to aerobic exercise but not in response to resistance exercise. Furthermore, athletic and lean adults have been shown to increase their energy intake in response to exercise, whereas no such response was observed in obese adults. There is also evidence that caloric restriction is associated with a decline in PA. Generally, humans seem to be better equipped to defend against weight loss than avoid weight gain, but results also show a large individual variability. Therefore, individual differences rather than group means should be explored to identify specific characteristics of "compensators" and "noncompensators." This review emphasizes the need for more research with simultaneous measurements of all major components contributing to energy balance to enhance the understanding of the regulation of energy balance, which is crucial to address the current obesity epidemic.

Appetite, appetite hormone and energy intake responses to two consecutive days of aerobic exercise in healthy young men

Single bouts of exercise do not cause compensatory changes in appetite, food intake or appetite regulatory hormones on the day that exercise is performed. It remains possible that such changes occur over an extended period or in response to a higher level of energy expenditure. This study sought to test this possibility by examining appetite, food intake and appetite regulatory hormones (acylated ghrelin, total peptide-YY, leptin and insulin) over two days, with acute bouts of exercise performed on each morning. Within a controlled laboratory setting, 15 healthy males completed two, 2-day long (09:00-16:00) experimental trials (exercise and control) in a randomised order. On the exercise trial participants performed 60 min of continuous moderate-high intensity treadmill running (day one: 70.1 ± 2.5% VO2peak, day two: 70.0 ± 3.2% VO2max (mean ± SD)) at the beginning of days one and two. Across each day appetite perceptions were assessed using visual analogue scales and appetite regulatory hormones were measured from venous blood samples. Ad libitum energy and macronutrient intakes were determined from meals provided two and six hours into each day and from a snack bag provided in-between trial days. Exercise elicited a high level of energy expenditure (total = 7566 ± 635 kJ across the two days) but did not produce compensatory changes in appetite or energy intake over two days (control: 29,217 ± 4006 kJ; exercise: 28,532 ± 3899 kJ, P > 0.050). Two-way repeated measures ANOVA did not reveal any main effects for acylated ghrelin or leptin (all P > 0.050). However a significant main effect of trial (P = 0.029) for PYY indicated higher concentrations on the exercise vs. control trial. These findings suggest that across a two day period, high volume exercise does not stimulate compensatory appetite regulatory changes.

Appetite control and energy balance: impact of exercise

Exercise is widely regarded as one of the most valuable components of behaviour that can influence body weight and therefore help in the prevention and management of obesity. Indeed, long-term controlled trials show a clear dose-related effect of exercise on body weight. However, there is a suspicion, particularly fuelled by media reports, that exercise serves to increase hunger and drive up food intake thereby nullifying the energy expended through activity. Not everyone performing regular exercise will lose weight and several investigations have demonstrated a huge individual variability in the response to exercise regimes. What accounts for this heterogeneous response? First, exercise (or physical activity) through the expenditure of energy will influence the energy balance equation with the potential to generate an energy deficit. However, energy expenditure also influences the control of appetite (i.e. the physiological and psychological regulatory processes underpinning feeding) and energy intake. This dynamic interaction means that the prediction of a resultant shift in energy balance, and therefore weight change, will be complicated. In changing energy intake, exercise will impact on the biological mechanisms controlling appetite. It is becoming recognized that the major influences on the expression of appetite arise from fat-free mass and fat mass, resting metabolic rate, gastric adjustment to ingested food, changes in episodic peptides including insulin, ghrelin, cholecystokinin, glucagon-like peptide-1 and tyrosine-tyrosine, as well as tonic peptides such as leptin. Moreover, there is evidence that exercise will influence all of these components that, in turn, will influence the drive to eat through the modulation of hunger (a conscious sensation reflecting a mental urge to eat) and adjustments in postprandial satiety via an interaction with food composition. The specific actions of exercise on each physiological component will vary in strength from person to person (according to individual physiological characteristics) and with the intensity and duration of exercise. Therefore, individual responses to exercise will be highly variable and difficult to predict.

Comparison of a very low-calorie-ketogenic diet with a standard low-calorie diet in the treatment of obesity

The global prevalence of obesity has significantly increased in most industrialized countries. Anti-obesity drugs are scarce, and indications to change their life style are impractical. Therefore, to identify diets able to produce significantly and maintained weight loss is mandatory. The present work evaluated the efficacy of a very low-calorie-ketogenic (VLCK) diet in obesity. A group of obese patients were randomized into two groups: the VLCK diet group and a standard low-calorie diet (LC group). The follow-up period was 12 months. Both groups received external support, counseling, to perform physical activity and adhered to the diet. The VLCK diet induced a 30-45 days of mild ketosis and significant effects on body weight within 15 days. At 2 months, the weight reductions in the VLCK diet and LC diet groups were 13.6 ± 3.9 and 4.8 ± 2.7 kg, respectively (p < 0.0001). At the end of the study, at 12 months, the weight reductions were 19.9 ± 12.3 and 7.0 ± 5.6 kg, respectively (p < 0.0001), and more than 88 % of patients in the VLCK diet group lost more of 10 % of their initial weight. Lean mass was practically unaffected. The VLCK diet was well tolerated and the side effects were moderate and transitory. In a group of obese patients, the VLCK diet was significantly more effective than a standard LC diet. At one year follow-up in the group with VLCK diet, most of the patients loss more than 10 % of their initial weight and lean mass was well preserved.

Exercise patterns, ingestive behaviors, and energy balance

Ingestive and exercise behaviors are important determinants of whole body energy balance and weight control. An acute bout of exercise generates a transient energy deficit, which is only partially compensated for by food intake at the next eating occasion or within the next day (loose dietary coupling). Such an energy deficit, when repeated chronically, leads to moderate weight loss and improved body composition. For this narrative review, we assessed the effects of exercise patterns on energy intake, energy balance, and weight control in adults primarily using results from randomized acute exercise and chronic training studies. The patterns assessed were exercise mode (e.g. resistance, aerobic exercise), intensity, duration, time of day, and frequency. The body of evidence indicates that exercise training frequency and quantity are influential for weight loss. Aerobic training is superior to resistance training for weight loss, although resistance training helps preserve lean body mass better. Weight loss does not differ among different intensities when energy expenditure is matched by adjusting duration. Differing patterns of physical activity exhibited by normal weight, overweight, and obese people during weekdays and weekend days are consistent with their weight status; leaner people are more physically active. Collectively, these findings support acute and chronic exercise patterns as important modifiable behaviors to improve energy balance and weight control in adults while having minor effects on absolute energy intake.

Active video games as a tool to prevent excessive weight gain in adolescents: rationale, design and methods of a randomized controlled trial

Background

Excessive body weight, low physical activity and excessive sedentary time in youth are major public health concerns. A new generation of video games, the ones that require physical activity to play the games –i.e. active games- may be a promising alternative to traditional non-active games to promote physical activity and reduce sedentary behaviors in youth. The aim of this manuscript is to describe the design of a study evaluating the effects of a family oriented active game intervention, incorporating several motivational elements, on anthropometrics and health behaviors in adolescents.

Methods/Design

The study is a randomized controlled trial (RCT), with non-active gaming adolescents aged 12 – 16 years old randomly allocated to a ten month intervention (receiving active games, as well as an encouragement to play) or a waiting-list control group (receiving active games after the intervention period). Primary outcomes are adolescents’ measured BMI-SDS (SDS = adjusted for mean standard deviation score), waist circumference-SDS, hip circumference and sum of skinfolds. Secondary outcomes are adolescents’ self-reported time spent playing active and non-active games, other sedentary activities and consumption of sugar-sweetened beverages. In addition, a process evaluation is conducted, assessing the sustainability of the active games, enjoyment, perceived competence, perceived barriers for active game play, game context, injuries from active game play, activity replacement and intention to continue playing the active games.

Discussion

This is the first adequately powered RCT including normal weight adolescents, evaluating a reasonably long period of provision of and exposure to active games. Next, strong elements are the incorporating motivational elements for active game play and a comprehensive process evaluation. This trial will provide evidence regarding the potential contribution of active games in prevention of excessive weight gain in adolescents.

Trial registration

Dutch Trial register NTR3228.

Does increased exercise or physical activity alter ad-libitum daily energy intake or macronutrient composition in healthy adults? A systematic review

BACKGROUND

The magnitude of the negative energy balance induced by exercise may be reduced due to compensatory increases in energy intake.

OBJECTIVE

TO ADDRESS THE QUESTION: Does increased exercise or physical activity alter ad-libitum daily energy intake or macronutrient composition in healthy adults?

DATA SOURCES

PubMed and Embase were searched (January 1990-January 2013) for studies that presented data on energy and/or macronutrient intake by level of exercise, physical activity or change in response to exercise. Ninety-nine articles (103 studies) were included.

STUDY ELIGIBILITY CRITERIA

Primary source articles published in English in peer-reviewed journals. Articles that presented data on energy and/or macronutrient intake by level of exercise or physical activity or changes in energy or macronutrient intake in response to acute exercise or exercise training in healthy (non-athlete) adults (mean age 18-64 years).

STUDY APPRAISAL AND SYNTHESIS METHODS

Articles were grouped by study design: cross-sectional, acute/short term, non-randomized, and randomized trials. Considerable heterogeneity existed within study groups for several important study parameters, therefore a meta-analysis was considered inappropriate. Results were synthesized and presented by study design.

RESULTS

No effect of physical activity, exercise or exercise training on energy intake was shown in 59% of cross-sectional studies (n = 17), 69% of acute (n = 40), 50% of short-term (n = 10), 92% of non-randomized (n = 12) and 75% of randomized trials (n = 24). Ninety-four percent of acute, 57% of short-term, 100% of non-randomized and 74% of randomized trials found no effect of exercise on macronutrient intake. Forty-six percent of cross-sectional trials found lower fat intake with increased physical activity.

LIMITATIONS

The literature is limited by the lack of adequately powered trials of sufficient duration, which have prescribed and measured exercise energy expenditure, or employed adequate assessment methods for energy and macronutrient intake.

CONCLUSIONS

We found no consistent evidence that increased physical activity or exercise effects energy or macronutrient intake.

Efficiency of a free-living physical activity promotion program following diet modification for fat loss in Japanese obese men

The aim of the current study was to examine the efficiency of a free-living physical activity promotion (PAP) program following a diet modification program for fat loss. Fifty obese men, aged 51.4±7.0 y, received a 6-mo regimen consisting of 2 phases. Weekly 90-min free-living PAP sessions were provided for 3 mo immediately after a 3-mo diet modification phase. Fat mass (FM) was measured at baseline and at months 3 and 6 using dual energy X-ray absorptiometry. The time spent in moderate-vigorous physical activity (MVPA) was monitored by a validated single-axis accelerometer. The total energy intake of all participants was assessed at baseline and during weeks 9 and 10 of both the diet modification and PAP programs. The change (Δ) in FM was -1.4±1.9 kg (p<0.05) during the PAP program after the diet modification program (-4.3±2.9 kg, p<0.01). Although there was no significant relationship between ΔFM and ΔMVPA during the PAP phase (p=0.11), MVPA was significantly increased during the PAP phase (+76.0±146.5 min/wk, p<0.01). However, a significant correlation was observed between energy intake/weight and MVPA during the PAP program (r=0.39). Our results suggest that the magnitude of expected FM loss induced by an increase in PA may be suppressed as a result of increased energy intake, even during a PAP program after a diet modification program.

Sex differences in the effects of mental work and moderate-intensity physical activity on energy intake in young adults

The aim of this study was to examine the acute effects of mental work and moderate-intensity physical activity on various components of energy balance in young and healthy adults. With the use of a randomized crossover design, 35 participants aged 24 ± 3 years completed three 45-min conditions, namely, (i) resting in a sitting position (control), (ii) reading and writing (mental work (MW)), and (iii) exercising on a treadmill at 40% of peak oxygen uptake (exercise), followed by an ad libitum lunch. The endpoints were spontaneous energy intake (EI), energy expenditure (EE), appetite sensations, and EI for the remainder of the day. We observed that the energy cost of the control and MW conditions was about the same whereas the exercise condition increased EE to a greater extent in men than women. Exercise induced a decrease in EI relative to EE compared to the control condition that was more pronounced in men than women. However, women tended to increase their energy intake after the MW condition compared to the control one whereas an opposite trend was observed in men. None of the appetite sensation markers differed significantly between both sexes. In conclusion, men and women have specific food intake patterns when submitted to cognitive and physical stimuli.

Contingency Management to Induce Exercise Among College Students

Objective: The effects of contingency management to induce physical activity levels were examined in seven non-obese physically inactive undergraduate students by providing monetary payments using a multiple baseline, changing-criterion procedure. Methods: Participants attended a baseline phase, a subsequent intervention phase consisting of three exercise sessions per week for 4 weeks, and a follow-up session 2 weeks post intervention. A total of $145 was available for attendance and exercise contingency payments. Results: Results indicate that all participants significantly increased exercise during intervention from inactivity at baseline to exercising three 30-minute sessions per week. Participants maintained some gains during follow-up. Limitations: The study employed a small and homogenous sample size and required participants to exercise in a lab setting thus limiting external validity. Conclusions: These findings suggest that incentive-based interventions are an effective and viable means for inducing exercise.

Obesity as malnutrition: the dimensions beyond energy balance

The aetiology of obesity is seemingly simple to understand: individuals consume more energy than they expend, with the excess energy being stored in adipose tissue. Public health campaigns therefore promote dietary restraint and physical exercise, and emphasize individual responsibility for these behaviours. Increasingly, however, researchers are switching from thermodynamic to metabolic models of obesity, thereby clarifying how specific environmental factors promote lipogenesis. Obesity can best be explained not by counting 'calories in and out', but by understanding how specific dietary products and activity behaviours perturb cellular metabolism and promote net lipogenesis. This metabolic approach can furthermore be integrated with more sophisticated models of how commercial practices drive the consumer trends that promote obesogenic behaviours. Notably, obesity treatment has proven more effective if it bypasses individual responsibility, suggesting that a similar approach placing less emphasis on individual responsibility would improve the efficacy of obesity prevention. Successful obesity prevention campaigns are likely to emerge only when the public receive better 'protection' from the commercial practices that are driving the global obesity epidemic. Rather than populations failing to heed governments' public health advice, governments are currently failing the public by abandoning their responsibility for regulating commercial activities.

The effects of sex, metabolic syndrome and exercise on postprandial lipemia

OBJECTIVE

Exercise has been suggested to have cardioprotective benefits due to a lowering of postprandial triglycerides (PPTG). We hypothesized that a morning exercise bout would significantly lower PPTG measured over a full day, in response to moderate fat meals (35% energy) in men more so than women, and in metabolic syndrome (MetS) relative to normal weight (NW) individuals.

MATERIALS/METHODS

Participants completed two randomized study days; one control and one exercise day (60 min of morning exercise, 60% VO(2peak)). Meals were consumed at breakfast, lunch and dinner with the energy expended during exercise replaced on the active day. The areas (AUC) and incremental areas (IAUC) under the curve were calculated for total triglycerides, total cholesterol and other metabolites.

RESULTS

Exercise did not significantly change the PPTG AUC & IAUC overall, or within, or between, each sex or group (NW and MetS). Exercise induced a 30% decrease in total cholesterol IAUC (p=0.003) in NW subjects. Overall, women had a lower IAUC for PPTG compared to men (p=0.037), with the greatest difference between MetS women and MetS men, due to a sustained drop in TG after lunch in the women. This suggests that PP, rather than fasting, lipid analyses may be particularly important when evaluating sex differences in metabolic risk.

CONCLUSIONS

With energy replacement, moderate morning exercise did not result in a significant decrease in PPTG excursions. Exercise did elicit a significant decrease in PP cholesterol levels in NW subjects, suggesting a potential mechanism for the cardioprotective effects of exercise.

Beneficial effects of 12 weeks of aerobic compared with resistance exercise training on perceived appetite in previously sedentary overweight and obese men

OBJECTIVE

To investigate the effect of 12 weeks of aerobic (AER) compared with resistance training (RES) on perceived hunger and fullness, together with appetite-related hormones in both the fasted state and postprandially.

METHODS

Thirty-three inactive, overweight and obese men (age 49±7 years; BMI 30.8±4.2 kg/m(2)) were allocated to either AER exercise (n=12), RES exercise (n=13) or a control group (CON; n=8). AER and RES completed 12 weeks of training (3 sessions per week), while CON continued their sedentary routine. Perceived hunger and fullness, together with appetite-related hormones (active ghrelin, leptin, insulin, pancreatic polypeptide (PP), and peptide tyrosine tyrosine (PYY)) were assessed pre and post-intervention in the fasted state and in response to oral glucose consumption (1284 kJ; 75 g carbohydrate).

RESULTS

Both AER and RES training elicited a decrease in fat mass (p<0.05), while CON did not. There was no difference in perceived hunger either in the fasted state (p>0.05) or in response to caloric consumption (p>0.05) following the intervention in any group. In contrast, both fasting and postprandial perceived fullness was higher following AER exercise (p<0.05), but not RES exercise or CON. These observations were not associated with alterations in fasting or postprandial active ghrelin, PP or PYY, although fasting and postprandial leptin was reduced following both AER and RES training (p<0.05).

CONCLUSION

Aerobic exercise training is associated with an increase in satiety, while an equivalent period of resistance training is not.

Lifestyle and high density lipoprotein cholesterol in postmenopause

OBJECTIVES

Menopause is characterized by hormonal and metabolic changes. These are linked to increased risk of cardiovascular disease, for which low blood plasma levels of high density lipoprotein (HDL) cholesterol are an independent risk factor. The present study investigated variables linked with basal plasma HDL cholesterol levels and the effects of aerobic training, on their variations, in 40 postmenopausal women.

METHODS

We assessed body composition, dietary habits and maximal aerobic capacity of participants. Characteristics of daily physical activity and plasma lipoproteins were measured. The women walked on 4 days/week, for 14 weeks, at moderate intensity, and they were grouped according to the resulting tertiles of basal plasma HDL cholesterol levels.

RESULTS

Logistic regression analysis showed that waist-to-hip ratio and number of daily bouts of moderate-intensity physical activity, held for at least 10 consecutive minutes (B10m/day), are predictive variables of basal plasma HDL cholesterol levels. After the training period, the first and second tertiles increased plasma HDL cholesterol levels, while the third tertile decreased plasma HDL cholesterol levels. The tertiles showed different remodelling of spontaneous physical activity: the third tertile reduced B10m/day, while the others did not.

CONCLUSIONS

This study provides knowledge about the relationships of plasma HDL cholesterol levels with characteristics of physical activity. Furthermore, it shows that physical exercise engagement can result in negative compensation of spontaneous physical activity that could counteract or reduce the positive effects of the aerobic training on plasma HDL cholesterol levels.

Effects of exercise before or after meal ingestion on fat balance and postprandial metabolism in overweight men

It is unclear how timing of exercise relative to meal ingestion influences substrate balance and metabolic responses. The present study aimed to compare the effects of exercise performed before or after breakfast on fat balance and postprandial metabolism. A total of ten sedentary overweight men (aged 28·1 (sem 10·7) years, BMI 29·0 (sem 2·8) kg/m2) underwent three trials in random order involving: (1) performing no exercise (CON), or walking for 60 min at 50 % maximal O2 uptake either (2) before (Ex-Meal) or (3) after (Meal-Ex) consuming a standardised breakfast meal. In each trial an ad libitum lunch was provided 3·5 h after breakfast. Substrate utilisation was assessed by indirect calorimetry and blood was taken at regular intervals over an 8·5 h observation period. At the end of the observation period, fat balances in the Ex-Meal ( − 1043 (sem 270) kJ) and Meal-Ex ( − 697 (sem 201) kJ) trials were both significantly lower than CON (204 (sem 165) kJ) and fat balance in the Ex-Meal trial was significantly lower than in the Meal-Ex trial (all P <0·0001). Compared with the CON trial, the 8·5 h postprandial TAG response was only significantly lowered in the Ex-Meal trial ( − 17 %, P =0·025) and not in the Meal-Ex trial ( − 11 %, P =0·20). Both the Ex-Meal and Meal-Ex trials showed significantly lowered insulin responses relative to the CON trial (by 19 and 24 %, respectively, P <0·01 for both). There were no differences in lunch energy intake between trials. The present findings suggest that there may be an advantage for body fat regulation and lipid metabolism in exercising before compared with after breakfast. However, further study is needed to determine whether the present findings extend over the long term under free-living conditions.

Energy intake and expenditure during sedentary screen time and motion-controlled video gaming

BACKGROUND

Television watching and playing of video games (VGs) are associated with higher energy intakes. Motion-controlled video games (MC) may be a healthier alternative to sedentary screen-based activities because of higher energy expenditures, but little is known about the effects of these games on energy intakes.

OBJECTIVE

Energy intake, expenditure, and surplus (intake - expenditure) were compared during sedentary (television and VG) and active (MC) screen-time use.

DESIGN

Young adults (n = 120; 60 women) were randomly assigned to the following 3 groups: television watching, playing traditional VGs, or playing MCs for 1 h while snacks and beverages were provided. Energy intakes, energy expenditures, and appetites were measured.

RESULTS

Intakes across these 3 groups showed a trend toward a significant difference (P = 0.065). The energy expenditure (P < 0.001) was higher, and the energy surplus (P = 0.038) was lower, in MC than in television or VG groups. All conditions produced a mean (±SD) energy surplus as follows: 638 ± 408 kcal in television, 655 ± 533 kcal in VG, and 376 ± 487 kcal in MC groups. The OR for consuming ≥500 kcal in the television compared with the MC group was 3.2 (95% CI: 1.2, 8.4). Secondary analyses, in which the 2 sedentary conditions were collapsed, showed an intake that was 178 kcal (95% CI: 8, 349 kcal) lower in the MC condition than in the sedentary groups (television and VG).

CONCLUSION

MCs may be a healthier alternative to sedentary screen time because of a lower energy surplus, but the playing of these games still resulted in a positive energy balance. This trial was registered at clinicaltrials.gov as NCT01523795.

Effects of food pattern change and physical exercise on cafeteria diet-induced obesity in female rats

Obesity affects a large number of people around the world and appears to be the result of changes in food intake, eating habits and physical activity levels. Changes in dietary patterns and physical exercise are therefore strongly recommended to treat obesity and its complications. The present study tested the hypothesis that obesity and metabolic changes produced by a cafeteria diet can be prevented with dietary changes and/or physical exercise. A total of fifty-six female Wistar rats underwent one of five treatments: chow diet; cafeteria diet; cafeteria diet followed by a chow diet; cafeteria diet plus exercise; cafeteria diet followed by a chow diet plus exercise. The duration of the experiment was 34 weeks. The cafeteria diet resulted in higher energy intake, weight gain, increased visceral adipose tissue and liver weight, and insulin resistance. The cafeteria diet followed by the chow diet resulted in energy intake, body weight, visceral adipose tissue and liver weight and insulin sensitivity equal to that of the controls. Exercise increased total energy intake at week 34, but produced no changes in the animals' body weight or adipose tissue mass. However, insulin sensitivity in animals subjected to exercise and the diet was similar to that of the controls. The present study found that exposure to palatable food caused obesity and insulin resistance and a diet change was sufficient to prevent cafeteria diet-induced obesity and to maintain insulin sensitivity at normal levels. In addition, exercise resulted in normal insulin sensitivity in obese rats. These results may help to develop new approaches for the treatment of obesity and type 2 diabetes mellitus.

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.

Using a novel computer-based approach to assess the acute effects of exercise on appetite-related measures

Measuring food intake using standard buffet meals can be complicated by sensory and external cues which can alter energy intake. The present study was designed to examine the effects of acute exercise on non-metabolic factors related to appetite and food intake using a computer-based assessment. Twenty-seven men and women participated in two sessions in random order: 60-min walking on the treadmill (exercise trial; EX) or seated rest (control trial; CON). Subjective hunger and fullness, food liking, food utility, and ideal portion size were assessed before and immediately after exercise or rest, and hourly for 2 h. The findings showed that an acute bout of moderate intensity exercise had an anorexigenic effect; characterised by diminished hunger (-17.4%, p=0.004) and lower prospective ideal portion size (-7.7%, p=0.003) compared to no exercise. This novel, computer-based assessment, is a useful alternative to buffet meals setting and allows for the determination of non-metabolic factors associated with feeding behaviour in relation to exercise.

Obesity and energy balance: is the tail wagging the dog?

The scientific study of obesity has been dominated throughout the twentieth century by the concept of energy balance. This conceptual approach, based on fundamental thermodynamic principles, states that energy cannot be destroyed, and can only be gained, lost or stored by an organism. Its application in obesity research has emphasised excessive appetite (gluttony), or insufficient physical activity (sloth), as the primary determinants of excess weight gain, reflected in current guidelines for obesity prevention and treatment. This model cannot explain why weight accumulates persistently rather than reaching a plateau, and underplays the effect of variability in dietary constituents on energy and intermediary metabolism. An alternative model emphasises the capacity of fructose and fructose-derived sweeteners (sucrose, high-fructose corn syrup) to perturb cellular metabolism via modification of the adenosine monophosphate (AMP)/adenosine triphosphate (ATP) ratio, activation of AMP kinase and compensatory mechanisms, which favour adipose tissue accretion and increased appetite while depressing physical activity. This conceptual model implicates chronic hyperinsulinaemia in the presence of a paradoxical state of 'cellular starvation' as a key driver of the metabolic modifications inducing chronic weight gain. We combine evidence from in vitro and in vivo experiments to formulate a perspective on obesity aetiology that emphasises metabolic flexibility and dietary composition rather than energy balance. Using this model, we question the direction of causation of reported associations between obesity and sleep duration or childhood growth. Our perspective generates new hypotheses, which can be tested to improve our understanding of the current obesity epidemic, and to identify novel strategies for prevention or treatment.

Voluntary exercise improves high-fat diet-induced leptin resistance independent of adiposity

The efficacy of exercise as primary prevention of obesity is the subject of intense investigation. Here, we show that voluntary exercise in a mouse strain susceptible to diet-induced obesity (C57B6J) decreases fat mass and increases energy expenditure. In addition, exercise attenuates obesity in mice fed a high-fat diet (HFD). Using FosB immunoreactivity as a marker of chronic neuronal activation, we found that exercise activates leptin receptor-positive neurons in the ventromedial hypothalamic nucleus, involved in homeostatic control of energy balance. FosB immunoreactivity in the ventromedial hypothalamic nucleus is decreased in sedentary mice exposed to HFD but is increased in exercised mice independent of adiposity. To determine whether the antiobesity effects of voluntary exercise improve central nervous system (CNS) leptin action, we measured the anorectic and weight reducing effects of intracerebroventricular (ICV) leptin in sedentary and exercised mice exposed to HFD (EH), as well as in sedentary mice that have been calorie restricted (SR) to match the fat mass of EH mice. ICV leptin was ineffective in lowering food intake and body weight (BW) in sedentary mice exposed to HFD mice. The anorectic potency of leptin was partially restored in EH and SR groups. However, ICV leptin significantly lowered BW in EH but not SR mice. Thus, exercise leads to the maintenance of a lower BW and leaner composition, as well as to improved CNS leptin action, independent of fat mass. These results support the notion that physical exercise directly influences the responsiveness of the CNS circuits involved in energy homeostasis by allowing the defense of a lowered BW.