I'd say just the desire for simple social connection, a bit of chill time and relaxation doing nothing demanding.
Intellect - I don't think so. Or not usually. Most people go to Quora for that.
Sex - I don't think so. The people on this part of the open board seem too different from one another, not likely to be compatible enough at the intimate levels of sex or romance. But I could be wrong. Several members have health problems like diabetes or heart conditions which means the physical apparatus fails to respond to stimuli. Others may have been on antidepressants long term and hence have zero desire. Some may have switched off on that level as the easiest way to deal with long term lack of a willing partner. There's an adult section on aM. Maybe some people find a way of connecting there. Similar Worlds probably provides more opportunities for online sexuality because it provides a filter for its members to choose the kind of engagement they want. It also has a huge membership base. Many are young adults - easy to tell by the immaturity of their questions and answers - and the intense emotional angst. Types who want more than an online experience could try E-Harmony or Tinder for live meetings.
Weight loss pills - possibly a few. I'm assuming weight loss pills (if not con-job placebos) contain ephedrine, amphetamines or caffeine. Loads of people love coffee on this site, especially the owner and founder, Just Asking or J.A. Friendly jokes about her coffee addiction pop up fairly frequently. Be sure never to say anything bad about coffee on this site. ;) So yes, some of the energy might be caffeine driven.
One or two (maybe more) come here when tanked up on grog - their questions and answers get noticeably sillier.