Targeting lifestyle energy expenditure in the management of obesity and health: from biology to built environment.

Increasing lifestyle energy expenditure has long been advocated in the prevention and treatment of obesity, as embodied in the ancient prescription of Hippocrates (the 'father of modern medicine') that people with obesity should eat less and exercise more. However, the long-term outcome of exercise alone or in combination with dieting in obesity management is poor. To understand the reasons underlying these failures and to develop novel strategies that target lifestyle energy expenditure in both prevention and treatment of obesity, research over the past decades has focused on (i) the interactions between physical activity and body weight (and its composition) throughout the lifespan; (ii) the influence of biology and potential compensatory changes in energy expenditure, food intake and food assimilation in response to energy deficits; and (iii) the impact of the built environment (outdoor and indoor) and smart technology on physical activity behaviours, thermoregulatory thermogenesis and metabolic health. It is against this background that recent advances relevant to the theme of 'Targeting Lifestyle Energy Expenditure in the Management of Obesity and Health: From Biology to Built Environment' are addressed in this overview and the nine review articles in this supplement, reporting the proceedings of the 9th Fribourg Obesity Research Conference.

Do gender and ethnic differences in fasting leptin in Indians and Creoles of Mauritius persist beyond differences in adiposity?

Recent body composition studies on the island of Mauritius in young adults belonging to the two main ethnicities-Indians (South Asian descent) and Creoles (African/Malagasy descent)-have shown gender-specific ethnic differences in their body mass index (BMI)-Fat% relationships. We investigated here whether potential gender and ethnic differences in blood leptin would persist beyond that explained by differences in body composition. In healthy young adult Mauritian Indians and Creoles (79 men and 80 women; BMI range: 15-41 kg m-2), we investigated the relationships between fasted serum leptin with BMI, waist circumference (WC), total fat% assessed by deuterium oxide dilution technique and central adiposity (trunk fat%) assessed by abdominal bioimpedance analysis. The results indicate that the greater elevations in leptin-BMI and leptin-WC regression lines in women compared with men, as well as in Indian men compared with Creole men, are abolished when BMI and WC are replaced by total body fat% and trunk fat%, respectively. In women, no significant between-ethnic difference is observed in total body fat%, trunk fat% and serum leptin. Thus, in young adult Mauritians, a population at high risk for later cardiometabolic diseases, the differences in body fat% entirely accounted for the observed gender and ethnic differences in serum leptin.

Isometric thermogenesis at rest and during movement: a neglected variable in energy expenditure and obesity predisposition.

Isometric thermogenesis as applied to human energy expenditure refers to heat production resulting from increased muscle tension. While most physical activities consist of both dynamic and static (isometric) muscle actions, the isometric component is very often essential for the optimal performance of dynamic work given its role in coordinating posture during standing, walking and most physical activities of everyday life. Over the past 75 years, there has been sporadic interest into the relevance of isometric work to thermoregulatory thermogenesis and to adaptive thermogenesis pertaining to body-weight regulation. This has been in relation to (i) a role for skeletal muscle minor tremor or microvibration - nowadays referred to as 'resting muscle mechanical activity' - in maintaining body temperature in response to mild cooling; (ii) a role for slowed skeletal muscle isometric contraction-relaxation cycle as a mechanism for energy conservation in response to caloric restriction and weight loss and (iii) a role for spontaneous physical activity (which is contributed importantly by isometric work for posture maintenance and fidgeting behaviours) in adaptive thermogenesis pertaining to weight regulation. This paper reviews the evidence underlying these proposed roles for isometric work in adaptive thermogenesis and highlights the contention that variability in this neglected component of energy expenditure could contribute to human predisposition to obesity.

Passive and active roles of fat-free mass in the control of energy intake and body composition regulation.

While putative feedback signals arising from adipose tissue are commonly assumed to provide the molecular links between the body's long-term energy requirements and energy intake, the available evidence suggests that the lean body or fat-free mass (FFM) also plays a role in the drive to eat. A distinction must, however, be made between a 'passive' role of FFM in driving energy intake, which is likely to be mediated by 'energy-sensing' mechanisms that translate FFM-induced energy requirements to energy intake, and a more 'active' role of FFM in the drive to eat through feedback signaling between FFM deficit and energy intake. Consequently, a loss of FFM that results from dieting or sedentarity should be viewed as a risk factor for weight regain and increased fatness not only because of the impact of the FFM deficit in lowering the maintenance energy requirement but also because of the body's attempt to restore FFM by overeating-a phenomenon referred to as 'collateral fattening'. A better understanding of these passive and active roles of FFM in the control of energy intake will necessitate the elucidation of peripheral signals and energy-sensing mechanisms that drive hunger and appetite, with implications for both obesity prevention and its management.

Body composition-derived BMI cut-offs for overweight and obesity in Indians and Creoles of Mauritius: comparison with Caucasians.

BACKGROUND AND AIMS: Global estimates of overweight and obesity prevalence are based on the World Health Organisation (WHO) body mass index (BMI) cut-off values of 25 and 30 kg m-2, respectively. To validate these BMI cut-offs for adiposity in the island population of Mauritius, we assessed the relationship between BMI and measured body fat mass in this population according to gender and ethnicity. METHODS: In 175 young adult Mauritians (age 20-42 years) belonging to the two main ethnic groups-Indians (South Asian descent) and Creoles (African/Malagasy descent), body weight, height and waist circumference (WC) were measured, total body fat assessed by deuterium oxide (D2O) dilution and trunk (abdominal) fat by segmental bioimpedance analysis. RESULTS: Compared to body fat% predicted from BMI using Caucasian-based equations, body fat% assessed by D2O dilution in Mauritians was higher by 3-5 units in Indian men and women as well as in Creole women, but not in Creole men. This gender-specific ethnic difference in body composition between Indians and Creoles is reflected in their BMI-Fat% relationships, as well as in their WC-Trunk Fat% relationships. Overall, WHO BMI cut-offs of 25 and 30 kg m-2 for overweight and obesity, respectively, seem valid only for Creole men (~24 and 29.5, respectively), but not for Creole women whose BMI cut-offs are 2-4 units lower (21-22 for overweight; 27-28 for obese) nor for Indian men and women whose BMI cut-offs are 3-4 units lower (21-22 for overweight; 26-27 for obese). CONCLUSIONS: The use of BMI cut-off points for classifying overweight and obesity need to take into account both ethnicity and gender to avoid gross adiposity status misclassification in this population known to be at high risk for type-2 diabetes and cardiovascular diseases. This is particularly of importance in obesity prevention strategies both in clinical medicine and public health.

Fasting substrate oxidation at rest assessed by indirect calorimetry: is prior dietary macronutrient level and composition a confounder?

Indirect calorimetry, the measurement of O2 consumption and CO2 production, constitutes an invaluable tool as the most common method for analyzing whole-body energy expenditure, and also provides an index of the nature of macronutrient substrate oxidation--namely, carbohydrate (CHO) versus fat oxidation. The latter constitutes a key etiological factor in obesity as this condition can only develop when total fat oxidation is chronically lower than total exogenous fat intake. The standardization of indirect calorimetry measurements is essential for accurately tracking the relative proportion of energy expenditure derived from CHO and fat oxidation. Here we analyze literature data to show that the average fasting respiratory quotient typically shifts from approximately 0.80 to 0.90 (indicating a doubling of resting CHO oxidation) in response to a switch in dietary CHO intake (as % energy) from 30 to 60%. This underscores the importance of taking into account dietary macronutrient composition prior to indirect calorimetry studies in the interpretation of data on substrate utilization and oxidation.

Dieting and weight cycling as risk factors for cardiometabolic diseases: who is really at risk?

Despite the poor prognosis of dieting in obesity management, which often results in repeated attempts at weight loss and hence weight cycling, the prevalence of dieting has increased continuously in the past decades in parallel to the steadily increasing prevalence of obesity. However, dieting and weight cycling are not limited to those who are obese or overweight as substantial proportions of the various population groups with normal body weight also attempt to lose weight. These include young and older adults as well as children and adolescents who perceive themselves as too fat (due to media, parental and social pressures), athletes in weight-sensitive competitive sports (i.e. mandatory weight categories, gravitational and aesthetic sports) or among performers for whom a slim image is professionally an advantage. Of particular concern is the emergence of evidence that some of the potentially negative health consequences of repeated dieting and weight cycling are more readily seen in people of normal body weight rather than in those who are overweight or obese. In particular, several metabolic and cardiovascular risk factors associated with weight cycling in normal-weight individuals have been identified from cross-sectional and prospective studies as well as from studies of experimentally induced weight cycling. In addition, findings from studies of experimental weight cycling have reinforced the notion that fluctuations of cardiovascular risk variables (such as blood pressure, heart rate, sympathetic activity, blood glucose, lipids and insulin) with probable repeated overshoots above normal values during periods of weight regain put an additional stress on the cardiovascular system. As the prevalence of diet-induced weight cycling is increasing due to the opposing forces of an 'obesigenic' environment and the media pressure for a slim figure (that even targets children), dieting and weight cycling is likely to become an increasingly serious public health issue.

How dieting makes the lean fatter: from a perspective of body composition autoregulation through adipostats and proteinstats awaiting discovery.

Whether dieting makes people fatter has been a subject of considerable controversy over the past 30 years. More recent analysis of several prospective studies suggest, however, that it is dieting to lose weight in people who are in the healthy normal range of body weight, rather than in those who are overweight or obese, that most strongly and consistently predict future weight gain. This paper analyses the ongoing arguments in the debate about whether repeated dieting to lose weight in normal-weight people represents unsuccessful attempts to counter genetic and familial predispositions to obesity, a psychosocial reaction to the fear of fatness or that dieting per se confers risks for fatness and hence a contributing factor to the obesity epidemic. In addressing the biological plausibility that dieting predisposes the lean (rather than the overweight or obese) to regaining more body fat than what had been lost (i.e. fat overshooting), it integrates the results derived from the re-analysis of body composition data on fat mass and fat-free mass (FFM) losses and recoveries from human studies of experimental energy restriction and refeeding. These suggest that feedback signals from the depletion of both fat mass (i.e. adipostats) and FFM (i.e. proteinstats) contribute to weight regain through the modulation of energy intake and adaptive thermogenesis, and that a faster rate of fat recovery relative to FFM recovery (i.e. preferential catch-up fat) is a central outcome of body composition autoregulation in lean individuals. Such a temporal desynchronization in the restoration of the body's fat vs. FFM results in a state of hyperphagia that persists beyond complete recovery of fat mass and interestingly until FFM is fully recovered. However, as this completion of FFM recovery is also accompanied by fat deposition, excess fat accumulates. In other words, fat overshooting is a prerequisite to allow complete recovery of FFM. This confers biological plausibility for post-dieting fat overshooting - which through repeated dieting and weight cycling would increase the risks for trajectories from leanness to fatness. Given the increasing prevalence of dieting in normal-weight female and male among young adults, adolescents and even children who perceive themselves as too fat (due to media, family and societal pressures), together with the high prevalence of dieting for optimizing performance among athletes in weight-sensitive sports, the notion that dieting and weight cycling may be predisposing a substantial proportion of the population to weight gain and obesity deserves greater scientific scrutiny.

Sitting comfortably versus lying down: is there really a difference in energy expenditure?

BACKGROUND & AIMS: Energy expenditure (EE) during sitting is widely assumed to be higher than that while lying down, but supporting evidence is equivocal. Despite this, resting EE in the sitting position is often used as a proxy for basal metabolic rate. Here we investigate whether EE differs in the comfortable seated position compared to supine (lying) position. METHODS: EE and respiratory quotient (RQ) were measured (by ventilated hood indirect calorimetry) in 19 healthy subjects (9 men, 10 women) after an overnight fast. Supine measurements were made using a comfortable clinical tilting table and sitting measurements made using an adjustable, ergonomic car seat adapted for the hood system. After about 30 min of rest in either position, metabolic monitoring was conducted until stabilization of EE for at least 15 min in each posture. RESULTS: EE in the sitting position was not significantly different compared to supine (<2% difference). By contrast, heart rate was higher by 7 beats/min (p < 0.05). RQ was slightly but significantly decreased during sitting compared to lying (p < 0.05), with no change in breathing rate. CONCLUSIONS: This study suggests that the ventilated hood calorimetry system for assessment of REE after an overnight fast in a comfortable sitting position can be used as a good proxy of the basal metabolic rate. It also underscores the applicability of the ventilated hood system to measurements of resting EE in the sitting posture which, compared to supine posture, may be more acceptable/convenient to the subject/patient participating in postprandial metabolic studies lasting several hours.

Objectively measured physical activity levels of Venetian adults.

AIM: Venice, Italy, provides a unique environment to study physical activity as there are no automobiles, and walking is the most common means of transportation. The purpose of the present investigation was to objectively assess the physical activity (PA) levels of residents in Venice, Italy, using an accelerometer. METHODS: Twenty-seven Venetians (12 men and 15 women, 48 ± 16 yr, 169.4 ± 6.6 cm, 71.7 ± 11.1 kg) had worn an accelerometer (Lifecorder Ex) for 7 consecutive days in order to determine daily number of steps, time spent in light (LPA), moderate (MPA), or vigorous intensity (VPA) and moderate to vigorous intensity (MVPA) as well as energy expenditure associated with PA (PAEE). The time for all PA and MVPA lasting at least 1 minute, 3 minutes, 5 minutes and 10 minutes were also assessed. RESULTS: The PAEE, number of steps, LPA, MPA, VPA and MVPA averaged over 7 days of week were 1575 ± 524 kJ∙day⁻¹, 11920 ± 3667 steps∙day⁻¹, 77 ± 23 min∙day 43 ± 19 min∙day⁻¹, and 45 ± 21 min∙day⁻¹. The time for MVPA lasting >10 min was 0.3 ± 0.9 min∙day⁻¹. CONCLUSION: The amount and intensity of PA in Venetian adults is substantially higher than in most other populations previously evaluated, particularly American adults. The effects of the highly active Venetian lifestyle on important health outcomes remain unclear, but warrant further investigation.

Adaptive thermogenesis in human body weight regulation: more of a concept than a measurable entity?

According to Lavoisier, 'Life is combustion'. But to what extent humans adapt to changes in food intake through adaptive thermogenesis--by turning down the rate of heat production during energy deficit (so as to conserve energy) or turning it up during overnutrition (so as to dissipate excess calories)--has been one of the most controversial issues in nutritional sciences over the past 100 years. The debate nowadays is not whether adaptive thermogenesis exists or not, but rather about its quantitative importance in weight homoeostasis and its clinical relevance to the pathogenesis and management of obesity. Such uncertainties are likely to persist in the foreseeable future primarily because of limitations to unobtrusively measure changes in energy expenditure and body composition with high enough accuracy and precision, particularly when even small inter-individual variations in thermogenesis can, in dynamic systems and over the long term, be important in the determining weight maintenance in some and obesity and weight regain in others. This paper reviews the considerable body of evidence, albeit fragmentary, suggesting the existence of quantitatively important adaptive thermogenesis in several compartments of energy expenditure in response to altered food intake. It then discusses the various limitations that lead to over- or underestimations in its assessment, including definitional and semantics, technical and methodological, analytical and statistical. While the role of adaptive thermogenesis in human weight regulation is likely to remain more a concept than a strictly 'quantifiable' entity in the foreseeable future, the evolution of this concept continues to fuel exciting hypothesis-driven mechanistic research which contributes to advance knowledge in human metabolism and which is bound to result in improved strategies for the management of a healthy body weight.

Does metabolic compensation explain the majority of less-than-expected weight loss in obese adults during a short-term severe diet and exercise intervention?

OBJECTIVE: We investigated to what extent changes in metabolic rate and composition of weight loss explained the less-than-expected weight loss in obese men and women during a diet-plus-exercise intervention. DESIGN: In all, 16 obese men and women (41 ± 9 years; body mass index (BMI) 39 ± 6 kg m(-2)) were investigated in energy balance before, after and twice during a 12-week very-low-energy diet(565-650 kcal per day) plus exercise (aerobic plus resistance training) intervention. The relative energy deficit (EDef) from baseline requirements was severe (74%-87%). Body composition was measured by deuterium dilution and dual energy X-ray absorptiometry, and resting metabolic rate (RMR) was measured by indirect calorimetry. Fat mass (FM) and fat-free mass (FFM) were converted into energy equivalents using constants 9.45 kcal per g FM and 1.13 kcal per g FFM. Predicted weight loss was calculated from the EDef using the '7700 kcal kg(-1) rule'. RESULTS: Changes in weight (-18.6 ± 5.0 kg), FM (-15.5 ± 4.3 kg) and FFM (-3.1 ± 1.9 kg) did not differ between genders. Measured weight loss was on average 67% of the predicted value, but ranged from 39% to 94%. Relative EDef was correlated with the decrease in RMR (R=0.70, P<0.01), and the decrease in RMR correlated with the difference between actual and expected weight loss (R=0.51, P<0.01). Changes in metabolic rate explained on average 67% of the less-than-expected weight loss, and variability in the proportion of weight lost as FM accounted for a further 5%. On average, after adjustment for changes in metabolic rate and body composition of weight lost, actual weight loss reached 90% of the predicted values. CONCLUSION: Although weight loss was 33% lower than predicted at baseline from standard energy equivalents, the majority of this differential was explained by physiological variables. Although lower-than-expected weight loss is often attributed to incomplete adherence to prescribed interventions, the influence of baseline calculation errors and metabolic downregulation should not be discounted.

Non-contact assessment of waist circumference: will tape measurements become progressively obsolete?

Waist circumference (WC) is a key variable to assess in health management as it is a proxy of abdominal fat mass and a surrogate marker of cardiometabolic disease risk, including the metabolic syndrome. Recently, a portable non-contact device calculating WC (ViScan) has been developed, which hence allows the tracking of WC independently of the inter-investigators error. We compared WC values obtained with this device with WC measured by simple non-stretchable tape in 74 adults of varying body mass indices (range 17-39 kg/m(2)). The correlation between the two methods was very high (r=0.97, P<0.0001) and the reproducibility (precision) assessed with a rigid phantom was excellent (<1 cm, coefficient of variability<1%). The instrument constitutes a potentially valuable tool for longitudinal surveys and comparative international studies, which require simple but precise measurements of WC in order to track the effect of subtle changes on various health outcomes.

Body composition phenotypes in pathways to obesity and the metabolic syndrome.

Dynamic changes in body weight have long been recognized as important indicators of risk for debilitating diseases. While weight loss or impaired growth can lead to muscle wastage, as well as to susceptibility to infections and organ dysfunctions, the development of excess fat predisposes to type 2 diabetes and cardiovascular diseases, with insulin resistance as a central feature of the disease entities of the metabolic syndrome. Although widely used as the phenotypic expression of adiposity in population and gene-search studies, body mass index (BMI), that is, weight/height(2) (H(2)), which was developed as an operational definition for classifying both obesity and malnutrition, has considerable limitations in delineating fat mass (FM) from fat-free mass (FFM), in particular at the individual level. After an examination of these limitations within the constraints of the BMI-FM% relationship, this paper reviews recent advances in concepts about health risks related to body composition phenotypes, which center upon (i) the partitioning of BMI into an FM index (FM/H(2)) and an FFM index (FFM/H(2)), (ii) the partitioning of FFM into organ mass and skeletal muscle mass, (iii) the anatomical partitioning of FM into hazardous fat and protective fat and (iv) the interplay between adipose tissue expandability and ectopic fat deposition within or around organs/tissues that constitute the lean body mass. These concepts about body composition phenotypes and health risks are reviewed in the light of race/ethnic variability in metabolic susceptibility to obesity and the metabolic syndrome.

Pre-pregnancy and pregnancy predictors of obesity.

Obesity has progressively become a global epidemic that constitutes one of the biggest current health problems worldwide. Pregnancy is a risk factor for excessive weight gain. Factors that may predict development of obesity in later life mainly include gestational weight gain, pre-pregnancy nutritional status, age, parity and race. Change in lifestyle factors, such as eating habits, enrollment in physical activity, smoking and duration of lactation, in addition to the above factors, may also contribute to the development of obesity but are still not fully understood. Women who retain more body weight after pregnancy have, in general, larger pregnancy body weight gain, higher pre-pregnancy body mass index, marked weight changes in previous pregnancies, lactate slightly less and stop smoking during pregnancy to a larger extent. In addition, irregular eating habits and decreased leisure time activity after delivery influence postpartum weight retention. Taking into consideration the epidemic of obesity, with all its adverse long-term consequences, there is an increasing need to promote counseling before, during and after pregnancy on the role of diet and physical activity in reproductive health.

Are pedometers adequate instruments for assessing energy expenditure?

OBJECTIVE: Assessing energy expenditure (EE) is important for the control of obesity. Daily step counts have become popular and constitute one practical technique for evaluating the physical activity (PA) in large population studies. However, information on the capacity of pedometers to track EE in free-living conditions remains scanty. SUBJECTS AND METHODS: The 24-h EE of 71 healthy adults was measured by indirect calorimetry in a large respiratory chamber. Two accelerometers were attached to the waist, one for counting the total daily steps (ACC(STEP)) and another for measuring the anteroposterior whole body acceleration calculated as the root mean square of the acceleration signal at every second (ACC(RMS)). RESULTS: The ACC(STEP) was not associated with PA-related EE (PAEE) or 24-h EE. Body weight (BW) was the main determinant of both the values (explaining 30 and 75% of the variance, respectively). Approximately 8% (P<0.001) of the variance in PAEE was attributed to the ACC(RMS) after BW was accounted for, whereas the ACC(STEP) did not explain any additional variance. A multiple stepwise regression analysis revealed that BW, height and ACC(RMS) were highly significant determinants of 24-h EE and accounted for as much as 83% of the total variance. CONCLUSIONS: Recording the number of steps per day does not provide accurate information on EE, and at best is only a crude predictor of the general PA in terms of displacement. In contrast, accelerometry signals are considered to be a more meaningful factor in the assessment of EE rather than step counts under sedentary conditions.

Pregnancy-related changes in activity energy expenditure and resting metabolic rate in Switzerland.

BACKGROUND/OBJECTIVES: To measure resting metabolic rate (RMR), activity energy expenditure (AEE), total energy expenditure (TEE) and physical activity pattern, that is, duration and intensity (in metabolic equivalents, METs) of activities performed in late pregnancy compared with postpartum in healthy, well-nourished women living in Switzerland. SUBJECTS/METHODS: Weight, height, RMR, AEE, TEE and physical activity patterns were measured longitudinally in 27 healthy women aged 23-40 years at 38.2+/-1.5 weeks of gestation and 40.0+/-7.2 weeks postpartum. RESULTS: The RMR during late pregnancy was 7480 kJ per day, that is, 1320+/-760 kJ per day (21.4%) higher than the postpartum RMR (P<0.001). Absolute changes in RMR were positively correlated with the corresponding changes in body weight (r=0.61, P<0.001). RMR per kg body weight was similar in late pregnancy vs postpartum (P=0.28). AEE per kg during pregnancy and postpartum was 40+/-13 and 50+/-20 kJ/kg, respectively (P=0.001). There were significant differences in daily time spent at METs<1.5 (1067 vs 998 min, P=0.045), at 2.5< or =METs <3.0 (58 vs 82 min, P=0.002) and METs> or =6 (1 vs 6 min, P=0.014) during pregnancy and postpartum, respectively. CONCLUSIONS: Energy expenditure in healthy women living in Switzerland increases in pregnancy compared with the postpartum state. Additional energy expenditure is primarily attributed to an increase in RMR, which is partly compensated by a decrease in AEE. The decrease in physical activity-related energy costs is achieved by selecting less demanding activities and should be taken into account when defining extra energy requirements for late pregnancy in Switzerland.

The effect of exercise, alcohol or both combined on health and physical performance.

Alcohol (ethanol) is consumed on a daily basis by a large fraction of the population, and in many countries, light-to-moderate alcohol consumption is considered as an integral part of the diet. Although the relationship between alcohol intake and obesity is controversial, regular consumption of alcohol, through its effects in suppressing fat oxidation, is regarded as a risk factor for weight gain, increased abdominal obesity and hypertriglyceridemia. Indeed, alcohol taken with a meal leads to an increase in postprandial lipemia-an effect on postprandial metabolism that is opposite to that observed with exercise. Furthermore, although regular exercise training and/or a preprandial exercise session reduce postprandial lipemia independently of alcohol ingestion, the exercise-induced reduction in postprandial lipemia is nonetheless less pronounced when alcohol is also consumed with the meal. Whether or not alcohol influences exercise and sport performance remains contradictory. It is believed that alcohol has deleterious effects on the performance, although it may contribute to reduce pain and anxiety. The alcohol effects on sports performance depend on the type and dosage of alcohol, acute vs chronic administration, the alcohol elimination rate as well as the type of exercise.

ADOS: an educational primary prevention programme for preventing excess body weight in adolescents.

OBJECTIVE: The prevalence of adolescent obesity has increased considerably over the past decade in Switzerland and has become a serious public health problem in Europe. Prevention of obesity using various comprehensive programmes appears to be very promising, although we must admit that several interventions had generally disappointing results compared with the objectives and target initially fixed. Holistic programmes including nutritional education combined with promotion of physical activity and behaviour modification constitute the key factors in the prevention of childhood and adolescent obesity. The purpose of this programme was to incorporate nutrition/physical education as well as psychological aspects in selected secondary schools (9th grade, 14-17 years). METHODS: The educational strategy was based on the development of a series of 13 practical workshops covering wide areas such as physical inactivity, body composition, sugar, energy density, invisible lipids, how to read food labels, is meal duration important? Do you eat with pleasure or not? Do you eat because you are hungry? Emotional eating. For teachers continuing education, a basic highly illustrated guide was developed as a companion booklet to the workshops. These materials were first validated by biology, physical education, dietician and psychologist teachers as well as school medical officers. RESULTS: Teachers considered the practical educational materials innovative and useful, motivational and easy to understand. Up to now (early 2008), the programme has been implemented in 50 classes or more from schools originating from three areas in the French part of Switzerland. Based on the 1-week pedometer value assessed before and after the 1 school-year programme, an initial evaluation indicated that overall physical placidity was significantly decreased as evidenced by a significant rise in the number of steps per day. CONCLUSION: Future evaluation will provide more information on the effectiveness of the ADOS programme.

Concept of fat balance in human obesity revisited with particular reference to de novo lipogenesis.

The measurement of fat balance (fat input minus fat output) involves the accurate estimation of both metabolizable fat intake and total fat oxidation. This is possible mostly under laboratory conditions and not yet in free-living conditions. In the latter situation, net fat retention/mobilization can be estimated based on precise and accurate sequential body composition measurements. In case of positive balance, lipids stored in adipose tissue can originate from dietary (exogenous) lipids or from nonlipid precursors, mainly from carbohydrates (CHOs) but also from ethanol, through a process known as de novo lipogenesis (DNL). Basic equations are provided in this review to facilitate the interpretation of the different subcomponents of fat balance (endogenous vs exogenous) under different nutritional circumstances. One difficulty is methodological: total DNL is difficult to measure quantitatively in man; for example, indirect calorimetry only tracks net DNL, not total DNL. Although the numerous factors (mostly exogenous) influencing DNL have been studied, in particular the effect of CHO overfeeding, there is little information on the rate of DNL in habitual conditions of life, that is, large day-to-day fluctuations of CHO intakes, different types of CHO ingested with different glycemic indexes, alcohol combined with excess CHO intakes, etc. Three issues, which are still controversial today, will be addressed: (1) Is the increase of fat mass induced by CHO overfeeding explained by DNL only, or by decreased endogenous fat oxidation, or both? (2) Is DNL different in overweight and obese individuals as compared to their lean counterparts? (3) Does DNL occur both in the liver and in adipose tissue? Recent studies have demonstrated that acute CHO overfeeding influences adipose tissue lipogenic gene expression and that CHO may stimulate DNL in skeletal muscles, at least in vitro. The role of DNL and its importance in health and disease remain to be further clarified, in particular the putative effect of DNL on the control of energy intake and energy expenditure, as well as the occurrence of DNL in other tissues (such as in myocytes) in addition to hepatocytes and adipocytes.