Fat Men's Club (#72)
Nowadays, weigh-ins usually refer to the weight control before a sporting event, like a box fight.
With body scales being available in many households, to weigh oneself is done priavtely. (Although some public scales are still in use, e.g. in baths. And for whatever reason they still charge you to use them...)
Anyhow, in the late nineteenth century, scales weren't readily available. Also not yet available for men: Fatshaming.
This led to the formation of social clubs, called Fat Men's Clubs. Members had to weigh at least 200lbs (91kg, just like the heavy-weight limit in boxing) and were usually wealthy. The clubs served primarily for networking and they organized numerous social activities like sports events (in which - I guess - the members were only spectators), balls and eating contests. The events usually started with a weigh-in with a prize for the heaviest. The clubs grew less popular in the 20th century, when obesity was more and more associated with bad health.