I have noticed most people I know in MLMs tend to be 1) white, 2)Christian, 3) middle aged, and 4)either moderately or extremely overweight (obese). I'm wondering what the connection is here. I know MLMs draw from a large segment of society, but seem to have higher proportion who fall into those 4 categories.

I haven't noticed that at all. It probably depends more upon the region you live in (southern and midwestern USA tend to have more obese people), what the particular MLM is (the new age/health food/supplement MLMs tend to attract health nuts who care about their appearance), and where the MLM is recruiting (churches are a logical place for them to recruit because there's a large base of acquaintances there).

I know people of all races, sizes and religions who are in MLMs. I was on a guru path (Hinduism-based) for years, and met many people who recruited for their MLMs in that circle and also at New Age gatherings.