In the early 17th century some men wore corset-like vests and waist cinchers to create a narrow waist to make their shoulders and chest appear wider. Fashion also called for men to wear slender trousers with a very trim waist.
Dandies were most likely to wear an exaggerated version of a corset as seen in this colored etching from the era. (Right)
Towards the mid-1850s corsets were increasingly seen as feminine and men who wore them were seen as effeminate. Corsets were seen as comical post 1850s as shown in this inking from the book "La comédie de notre temps" By Bertall. Rough translation "The comedy of our times" which is a pencil and pen study of some fashions from the 1870s. (Below)
Some magazines also tried to sell corsets for men as athletic necessities. Fashion designer Charles Frederick Worth (of the Worth dresses, more on those another time) commented in Fashion that the trend to think corsets were primarily worn by dandies was untrue as he observed many athletic and active men such as soldiers also sought after the accessory.
In the 1900s the male corset was advertised as a belt for sportsmen similar to a weightlifter's belt or a surgical corset worn for health.