Utilisation des lipides : oxydation ou stockage ?

The stability of body weight and composition requires an equilibrium between the intakes and outputs of energy and macronutrients. Fat mass depends on the equilibrium between the input and output of lipid but also on the metabolic fate of lipids (oxidation or storage). Examination of metabolic pathways and of their regulation shows that cells have efficient biochemical and molecular mechanisms to stimulate acutely and on the long term carbohydrate oxidation, lipogenesis and lipid storage and to inhibit lipid oxidation. On the contrary, the ability of cells to acutely stimulate lipid oxidation is limited. These differences in regulation of lipid and carbohydrate metabolism are also present at the whole body level. The ability to increase lipid oxidation in response to an increased lipid intake is still more reduced in obese subjects. Despite numerous attempts to develop pharmacological approaches, modifications of dietary intakes and physical exercise remain the best ways to reduce lipid storage and to increase fat oxidation.     

Altérations hormonales et métaboliques lors du travail en horaires décalés

The development of nocturnal socio-professional activities has followed the expansion of artificial lighting, a characteristic of the modern world. Currently, a fifth of the active population work in shifted schedules or during night. The psychological, relational and social repercussions of this shift are obvious and well demonstrated. These situations are also associated with various health problems : sleep and vigilance disturbances, digestive disorders, metabolic abnormalities and cardiovascular morbidity. From 20% to 50% of the night-workers cease their night occupation invoking health problems. If the origin of these abnormalities is not univocal, different data indicate that shift-work led to a desynchronization of the circadian rhythms, source of hormonal and metabolic disturbances that may partly explain the clinical disorders. All occurs as if the circadian system of these subjects was in a phase of compromise between the requirements of their night activity and the maintenance, at least during the weekend, of a social and family diurnal activity. The debt of sleep frequently observed in these subjects may also play a role, which underlines the interactions between sleep and nutrition.     

L’Homme, victime de son cerveau ?

Is the obesity pandemia resulting from an inadequate human physiology faced to a changing alimentary environment or is it the consequence of his own peculiarities leading him to build himself an unadapted environment, thus differing from animals like apes (monkeys)?We propose an enlarged conceptual organization of the regulation of food intake and body mass. It would imply four partners. The level of energy intake, metabolic energy utilisation, the level of fat stores and functional digestive ability. Each of these four players would be a controlled variable in relation to the three others and at the same time working towards their control in a system in dynamic equilibrium. They would be under the permanent control of a central integrator able to limit the variation of the center of gravity of the system in acceptable bounds relatively to an individual set point.A number of physiologic knowledges support this concept and we may insist on the role of visceral sensitivity and central integration. The refinement of the regulation of our integrity offering important adaptative mechanisms lead us to consider that human physiology is able to cope with usual changes of our alimentary environment.By exploring what coud differenciate humans from animals, particularly apes, the idea arises that humans could be victimized by his cognitive capabilities and more particularly by his communicative capabilities. Able to construct and to infer from incomplete knowledge he is capable to build up an unadapted environment driving him to destruction.Again, whatever their illusions human beeings cannot infrige their physiologic limits.     

Morphologie et alimentation de l’enfant : Évolution au cours des dernières décennies

Growth is a favourable period to study the association between environmental factors and body composition, as many body parameters can be investigated. The analysis of secular trends in nutrition and growth could suggest hypotheses about the factors responsible for the body parameter changes over time.We have conducted several studies at different periods to assess secular trends. We also have developed growth indicators such as the BMI growth curves, the adiposity rebound and the arm muscle and arm fat areas.Since many years, increased stature has been recorded in various countries. The same trend was recorded in our studies. Mean stature in 2000 was 1.31m and 1.30m in 8-year-old boys and girls respectively. In 1960, in the French reference study, these figures were 1.27 and 1.26m, corresponding to a 4cm increase over the last 40 years. A comparison between two longitudinal studies conducted 30 years apart, indicates that the higher stature recorded at adult age in the more recent study, mainly results from an increase stature in early life. This increase mainly results from increased leg length. Birth weight recorded in studies conducted at different periods did not reveal any changes. By contrast, in school children, an increase in weight has been recorded in the last decades. Studies conducted in 10-year-old children at different time periods revealed that the prevalence of overweight defined by the 97^th centile of the French reference values was about 3% in 1965, 6% in 1980, 12% in 1995 and 16% in 2000. The age at adiposity rebound was 6.2 years in children born in 1965 and 5.6 in those born 30 years later. The earlier rebound recorded in the more recent study reflects an acceleration of growth.While children are taller, fatter, and grow faster, mean energy intake decreases over time, particularly due to a decrease in fat intake. The infant diet in many countries (by the age of 6-12 months) is characterised by high levels of proteins and low levels of fat. The high protein diet in infancy could explain the rapid growth process observed nowadays. Various studies have suggested that an accelerated growth in early life is associated with risk factors. Like in adults, obesity in children, is associated with metabolic diseases.In conclusion, growth is the period when environmental factors can have long lasting influence on body composition. The secular trends reported in many countries, such as increased stature, accelerated growth or the increasing prevalence of obesity, could result from influences taking place early in life. It is then important to develop research focussing on the identification of the early environmental factors which influence adult health.     

Lieu de contrôle chez les obèses : traduction et première étude de validation de l’échelle du lieu de contrôle du poids de saltzer

The objectives of this study are to enable the use of the concept of locus of control in the treatment of obese subjects and to verify if the presence of an alimentary disorder influences the belief in the weight’s control. The translation and validation in French is also part of the objective. We translated into French Saltzer’s specific scale of Weight Locus of Control (WLOC: weight locus of control) and then examined it’s validity. Then we compared it on general scales of the place of control (IPC of Levenson and SOC-3 of Paulhus). The subjects were both classified according to the presence of eating disorders (ED). A sample of 46 obese women (IMC>30) was tested, 20 of them without ED, and 26 with, associated to the presence ED, according to the criteria of the DSM-IV.The internal validity of WLOC is rather satisfactory. It correlates negatively with internality (IPC), personal control and interpersonal control (SOC-3). ED at the obese subjects are related on the externality of weight control and the externality of personal control. Obese subjects without ED believe more in weight control by themselves and personal control that the obese subjects with ED (Eating Disorders). Finally the scale of weight locus of control (WLOC) remains the most adapted in the treatment and the study of the obese subject.     

Éducation et prévention de l’obésité de l’enfant. bilan des études en population

The prevalences of overweight and obesity are increasing in France as well as in many countries around the world. Results of randomised controlled primary prevention studies in schools are summarized. They show the feasibility of improving school meals and energy expenditure during PE classes. However, the effect on overweight and obesity prevention are often modest. It is clear that the out-of-school life can totally compensate the effect of an intervention at school. Studies that have been able to modify the children's sedentary and active behaviours out of school have shown the most promising results. The National Nutrition and Health Plan in France comprises a set of actions targeting the whole population, from young children to the elderly, for several years. In that context, we may hope that the different actions undertaken in France including those at school will end with more favourable results.     

Rôles physiologiques des endocannabinoïdes dans le contrôle de l’homéostasie énergétique

Endocannabinoids are endogenous lipids which modulate the release of neurotransmitters and activate different signaling pathways, through the binding to cannabinoïd receptors, CB1 and CB2. Endocannabinoids are involved in the control of a variety of behavioural and neuroendocrine functions, including feeding behaviour. In the central nervous system, they essentially modulate the expression of orexigen or anorexigen neuropeptides thus resulting in the stimulation of food intake. Their peripheral targets are mainly the liver and the white adipose tissue where they stimulate lipogenesis, through the modulation of several enzymes and proteins expressions. Cannabinoïd receptor agonists are nowadays prescribed to improve appetite of people suffering from cancer or AIDS. In the same way, CB1 antagonist, such as Rimonabant, could provide efficient treatment of obesity.     

Obésité, corpulence et souci de minceur: inégalités sociales en France et aux États-Unis

Obesity is not comparable in France and in the United States, from its width, its evolution, its age and gender distribution. Between 1970 and 2000, obesity progressed very quickly in the United States, whereas we can observe a stability in France until the middle of the 1990′s, then a deterioration. For as much, for 30 years, the relations between obesity among women - and more largely corpulence - and social hierarchy have been marked in the two countries: obesity concerns more the people - especially the women - of the working-class categories, the least rich and the least graduate people. With equal corpulence, people of the working-class categories, even if they share some of the standards of thinness, are much less concerned about excesses of weight: the women most touched by obesity belong to the groups where the average corpulence is highest and where the attention to weight is the least strong. A preventive policy of public health concerning the members of theses working-class categories could be a good objective.     

Quelques aspects de la motivation à manger en fonction de l’index de masse corporelle (de la maigreur à l’obésité massive) dans un groupe de 2 509 adultes

This study examines how chronic dietary restraint, disinhibition, and hunger, as assessed by the Eating Inventory (also called the “Three Factor Eating Questionnaire”), vary over a broad range of Body Mass Index (BMI) values from leanness to massive obesity, in subjects with family obesity. EI factors were also studied as a function of personal weight history. Subjects were 2509 participants in a genetic study of obesity. BMIs ranged from 15 to 87kg/m². Multivariate analyses showed that restraint and disinhibition were significantly associated with the BMI in men, while only disinhibition was in women. Further analyses were performed after subdividing the population in 6 BMI groups. Disinhibition scores correlated strongly with hunger scores in both genders in all BMI categories; dietary restraint tended to correlate with the other two factors positively in leaner subjects, and negatively in highest BMI categories. The highest restraint scores were observed in nonobese adult women with previous obesity in childhood and/or adolescence, suggesting a beneficial influence of restraint on body weight loss. The role of behaviors associated with disinhibition in the development of body adiposity deserves further investigation.     

De quelques maux de la prévention contemporaine. Le cas de l’obésité et du surpoids

Overweight and obesity are considered major public health issues, and many preventive campaigns are designed to prevent unhealthy eating habits among the French. But these campaigns may be ineffective, and even sometimes counterproductive. Firstly, because prevention is a moral enterprise that can lead to stigmatizing targeted people. Secondly, because the ‘merchandization’ of prevention fuels a ‘dietary cacophony’. Thirdly, the medicalisation of overweight/obesity involves some shortcomings: it can prevent us from understanding eating habits, and many general physicians are insufficiently trained to take care of overweight or obese patients.     

Obésité sarcopénique et altérations du métabolisme protéique musculaire

The increasing prevalence of obesity among elderly people has led to the definition of the concept of sarcopenic obesity. This concept is defined as the potential to combine muscle metabolic changes associated with both aging and obesity. Several definitions have been proposed, but the absence of a consensus led to great variability in the prevalence of this phenomenon in literature. However, the proportion of the older obese population is not negligible, representing 5 to 15% of elderly people. The study of metabolic abnormalities associated with sarcopenic obesity is of importance, since these subjects are at increased risk of developing functional disability. However, very few studies evaluated the mechanisms involved in the cumulating and aggravating effect of obesity in the elderly, particularly at muscle level. Of note, significant alterations of muscle protein anabolism were observed in elderly people but also in obese subjects. Impairment in muscle protein metabolism, including protein synthesis rate, could be involved in the loss of functional capacity during sarcopenic obesity.     

Alimentation, activité physique et surpoids chez des enfants de l’est Algérien

The prevalence of overweight and obesity were measured in a sample of 251 children aged 8 to 12 year in an urban area of the Eastern part of Algeria. IOTF references are used in order to define overweight and obesity.The overall prevalence of overweight and obesity is 21.5 %. 15.9 %. Overweight alone is found in 15.9% and obesity in 5,6 % of the children. Obese children consume less often a breakfast and less milk than that normal weight children and eat more often high fat, high carbohydrates foods. Mean caloric intakes are similar. Meals and snacking take often place while watching television. Energy percent derived from proteins but not their absolute amount and fat intakes are higher in overweight children. Most of the overweight children (78 %) do not practice any sport activity. Fat intake adjusted on energy intake is positively correlated with sport duration.This preliminary study suggest that childhood obesity is now a public health threat in Algeria.     

Évaluation des apports alimentaires d’adolescents obèses et post-obèses : comparaison de la méthode iconographique SU.VI.MAX à la méthode de pesée des aliments

The objectives of this study were 1) to validate the SU.VI.MAX iconographic method against the weighed diet record method to assess food and nutrient intakes in obese and post-obese adolescents, and ; 2) to determine the effects of dietetic education on the precision of this method. Energy and nutrient intakes were determined by both methods in 26 institutionalised obese adolescents over 7-day-periods before the beginning and at the end of a weight-reduction programme, and 4 months later. The mean food, energy, carbohydrate, protein, and lipid intakes as assessed by the two methods were not significantly different, but the limits of agreement between the two methods were high. Obese and post-obese adolescents underestimated intake of their favourite meals (pasta, fried potatoes…) but often overvalued intake of vegetables, milk and hard cheese. The SU.VI.MAX iconographic method is, therefore, a reliable method to assess energy and nutrient intakes of obese and post-obese adolescents in epidemiologic studies, but it is unappropriate for assessment in individuals. In addition, dietetic education resulted in 50% decreases in the mean difference, and in the inter-individual differences in energy intake between the two methods.