Treat human beings or any organisms as biological machines. Here, many chemicals (hormones, for instance) regulate many processes in such machines. Whatever one has eaten so far, genetic history, environment, etc have changed hormones to a level where the model of dieting and working out doesn't work any longer. So, semaglutide and tirzepatide work on such regulatory hormones (GLP-1, GIP). In other words, what this research tells us that humans are not controlled by their personal will.