continues... European Journal of Clinical Nutrition advance online publication, 20 July 2011The 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 AMPkinase 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.
...In other words, Open your minds people!The aim of our review is not to claim that our revised model is correct or definitive, but rather to stimulate researchers to acknowledge that the direction of causation in obesity aetiology is less clear than is commonly assumed.Nothing that we propose in this article contradicts the laws of thermodynamics or the energy balance equation; rather,we follow others in questioning whether simplified interpretation of the energy balance equation can become misleading with regard to obesity causation. We suggest that if empirical work specifically addresses this dilemma,regardless of which model proves most compatible with data, the evidence base for obesity prevention is likely to improve.
Horizon explores the secrets of what makes a long, healthy and happy life. It turns out that a time you can't remember - the nine months you spend in the womb - could have more lasting effects on you today than your lifestyle or genes. It is one of the most powerful and provocative new ideas in human science, and it was pioneered by a British scientist, Professor David Barker. His theory has inspired a field of study that is revealing how our time in the womb could affect your health, personality, and even the lives of your children.
