Metabolism. There isn’t perhaps a more frequently used word in the weight loss (and weight gain) vocabulary than this. Indeed, it’s not uncommon to overhear people talking about their struggles – or triumphs – over the holiday bulge or love handles in terms of whether their metabolism is working, or not. Doctors, too, often refer to metabolism when they try and explain why starvation and water-loss diets aren’t scientifically of medically responsible; since, alas, they do not influence or take into account metabolism (there’s that word again!).