Prescription medication works mostly by helping you stay on a low carb diet, without cheating so much. Any weight loss diet that works, will likely be lower in carbohydrates than what you were eating, before you went on a diet to lose weight. Prescription medication does not make you lose weight, but helps you stay on your diet by decreasing your hunger (phentermine, phendimetrazine, diethlypropion, benzephetamine) and decreasing your sweet and starch cravings (Topemax, Zonegran, Naltrexone, Wellbutrin, DPP4 inhibitors plus Metformin, Victoza, Byetta, Symlin, Bydureon, Vitamin D). You don’t need to take prescription medication to lose weight. But prescription medication generally makes weight loss faster and easier, because you’re able to follow your diet with much less cheating.