Quantifying Energy Intake Changes during Obesity Pharmacotherapy

OBJECTIVE Despite the fact that most obesity drugs primarily work by reducing metabolizable energy intake, elucidation of the time course of energy intake changes during long-term obesity pharmacotherapy has been prevented by the limitations of self-report methods of measuring energy intake. METHODS A validated mathematical model of human metabolism was used to provide the first quantification of metabolizable energy intake changes during long-term obesity pharmacotherapy using body weight data from randomized, placebo-controlled trials that evaluated 14 different drugs or drug combinations. RESULTS Changes in metabolizable energy intake during obesity pharmacotherapy were reasonably well-described by an exponential pattern comprising three simple parameters, with early large changes in metabolizable energy intake followed by a slow transition to a smaller persistent drug effect. CONCLUSIONS Repeated body weight measurements along with a mathematical model of human metabolism can be used to quantify changes in metabolizable energy intake during obesity pharmacotherapy. The calculated metabolizable energy intake changes followed an exponential time course, and therefore different drugs can be evaluated and compared using a common mathematical framework.