From what I can see, there are a number of distinct types of people who do cycle for transport:
People who appear to have little money. No helmet, normal clothes. These people tend to ride battered supermarket ‘mtbs’, often with fewer than two working brakes (occasionally no working brakes) This type are mostly men, but I do see quite a few women, many appear Eastern European. These people are not fat.
‘Respectable’ (non-working?/retired) older ladies riding around suburbs. No helmet, normal clothes. Shopping bikes with baskets. Not fat.
Professional/technical middle-class types. Mostly men, but there are some women. They wear helmets and bike gear, ride flash road bikes or they ride tourers, CX’s or hybrids (many singlespeed, some fixed) with practical fittings -mudguards, racks, lights, child carriers etc. Some take children to school/nursery and commute significant distances. These people are not fat either.
Almost everybody else drives everywhere. Many of these people are fat.