Wear three-button blazers.
Avoid one- and two-button blazers. Instead, go for blazers with three buttons. They are just as classic as two-button blazers, but they will elongate your body and make you appear taller and, therefore, thinner. As well, always leave the top button on your blazer undone as it will stop your clothes from pulling, particularly in the area around your middle, and consequently, your movement will seem less restricted.