Obesity has become a worldwide epidemic and limiting one's food intake, or dieting, is usually unsuccessful. The purpose of the study was to explore the effect of food addiction (FA) on the current clinical and behavioral epidemic of obesity. FA, synonymous with food-dependency, is tentatively defined as an eating disorder based on substance dependence, as defined by the Diagnostic and Statistical Manual of Mental Disorders. Measurement of FA has been operationalized by the Yale Food Addiction Scale (YFAS) by applying the diagnostic criteria of substance dependence to eating behaviors. This study was based on the biological theory of chemical addiction and the evidence that highly processed, high-fat, and high-sugar foods may be addictive and may contribute to unsuccessful dieting. To explore the difficulty of adhering to healthy food choices, 6 women were identified who satisfied the diagnostic criteria of FA using the YFAS. These women were invited to participate in a qualitative study. The full transcripts, which were coded via interpretative phenomenological analysis, revealed 6 major themes. The most salient master themes were the loss of control over food intake, the need for external control for successful weight loss, and the significant distress caused by food and eating. All the women interviewed agreed that FA is an eating disorder and that (a) best results were obtained from sugar and flour abstinence and (b) success was found in a 12 Step program for FA based on an addiction model. Once identified with the YFAS, FA has a large impact for social change. Those recognized as having a FA can be offered a specific treatment, based on an addiction model, which differs from the usual treatment for obesity and offers a solution for successful weight management.

When intraspecific individuals differ in resource intake, scramble competition occurs among inferior individuals growing food-dependently. Scramble can be released through predation mortality. As a consequence of this release, production rates in inferior individuals increase and biomass overcompensation in the subsequent life-stages may occur. When intraspecific individuals do not differ in their resource intakes biomass overcompensation does not occur. If an individual changes its resource intake over ontogeny, the balance of intake and losses, its energetics, will change over ontogeny. Furthermore, differences will arise between the energetics of different life-stages. The predominant volume of interspecific competition theory is based on studies assuming no stage-specific differences in energetics, neglecting the influence of ontogeny on community dynamics altogether. We study how an stage-specific differences in energetics affect expectations from conventional competition theory. We use a stage-structured biomass model consistently translating individual life history processes, in particular food-dependent growth in body size, to the population level. The stage-structured population can be reduced to an unstructured population, if the energetics of all individuals are assumed to be equal.  The stage-structured model, however can also describe population dynamics when this equality is broken. We use the stage-structured biomass model to contrast the stage-specific differences resulting in a stage-structured population model, with an unstructured population model assuming no differences between stages. We show that stage-specific differences in energetics can affect competition on various trophic levels. I: In stead of outcompeting each other, a predator can be facilitated by another preying a scrambling prey life-stage of the same prey population. II: In coexistence with their prey, omnivores with an ontogenetic diet shift, where juvenile omnivores feed on resource and adults on prey, affect community structure only as predators, not as competitors to their prey. We show coexistence of omnivore and prey is not possible if the dominating interaction is competition. Feeding on prey, however, alleviates competition with prey and facilitates the introduction of omnivores. III: An ontogenetic diet shift creates niche partitioning, where without it this would result in neutral coexistence of two consumers competing for two resources. IV: Furthermore, predators can change resource requirements of diet shifters such that diet shifters can reduce resources to lower equilibria and sustain higher predator biomass than consumers without stage-specific differences in energetics. / LEREC

L’Afrique Subsaharienne avec une croissance démographique urbaine spectaculaire et une agriculture vivrière déficitaire n’a plus la capacité de nourrir la totalité de ses habitants : résultat des politiques de développement mis en place depuis les indépendances. Pour faire face à une demande alimentaire sans cesse croissante, surtout au niveau des zones urbaines, les pays subsahariens en général et le Gabon en particulier, grâce à son économie de rente, a recours aux importations massives de produits alimentaires souvent éloignés, voire incompatibles avec les habitudes alimentaires et/ou des us et coutumes des populations endogènes. Cependant, le Gabon contrairement à bon nombre de pays subsahariens, dispose d’importantes potentialités agricoles susceptibles de lui assurer aujourd’hui sa souveraineté alimentaire (climat, végétation, sols, réseau hydrographique, faible densité de population, etc.). Or, la récente crise économique mondiale à l’origine d’une crise alimentaire internationale sans précédent qui a d’ailleurs provoqué des émeutes de la faim dans plusieurs pays subsahariens, vient une nouvelle fois interpeller non seulement les autorités de l’Afrique Noire, mais aussi la communauté internationale toute entière quant à l’urgente nécessité d’un développement agricole vivrier local africain. En somme, la fragilité de la sécurité alimentaire mondiale, les stratégies géopolitiques des pays du Nord, la spéculation agricole internationale et la situation des économies africaines ont orienté notre réflexion sur la dépendance alimentaire excessive des pays subsahariens, à l’instar du Gabon, et nous ont conduits à revisiter dans cette thèse ce que pourrait être une politique de la souveraineté alimentaire. Cette démarche stratégique apparaît, au vu de ce qui précède, comme une nécessité politique, économique, culturelle et environnementale si l’on entend freiner, voire limiter au maximum, la dépendance alimentaire excessive et si l’on entend assurer un développement durable de cette région en général et du Gabon en particulier. / Having a spectacular urban population growth and an overdrawn food-producing agriculture (farming), Sub-Saharan Africa cannot feed the totality of its inhabitants any more. This is the result of development policies set up since independence. To face a continuous increasing food demand, especially in urban zones, sub-saharan countries in general, and Gabon in particular -thanks to its economy of pension- rely on massive import of food products, often from far abroad and incompatible with the food habits and\or habits and customs of the endogenous populations. However, Gabon, unlike most of sub-saharan countries, disposes of important agricultural potentialities susceptible to insure today its food sovereignty (climate, vegetation, grounds, water system, low density of population, etc.). But the recent world economic crisis, which is at the origin of an unprecedented international food crisis, causing riots of hunger in several sub-saharan countries, is once again calling the vigorous attention of not only African authorities, but also of the whole international community regarding a fierce urgency to promote the development local food-producing agriculture in Africa. In fact, the fragility of the global food safety, the geopolitical strategies of Western countries, the international agricultural speculation and the situation of the African savings guided our reflection on the excessive food dependence of sub-saharan countries, as for Gabon, and led us revisit in this thesis what could be a policy of food sovereignty. Considering what precedes, this strategic approach appears as a political, economic, cultural and environmental necessity if we intend to break or limit the most as possible the excessive food dependence and insure a sustainable development in this region in general and Gabon in particular.