Causal effects between subjective wellbeing and cardiometabolic health

The title is somewhat misleading; they looked for causal effects from subjective wellbeing to cardiometabolic health and vice-versa, but the only such effect that they found was in particular BMI-->subjective wellbeing (and with the sign you'd expect.)

That is very much in line with what you'd expect, I guess.

If you are and feel in good shape you report a higher level of wellbeing than if you aren't...

It's not necessarily a given that if your body is functioning well that you will be able to consciously report that you feel well. Would you know if your liver was operating at borderline unhealthy levels?

Yes, that also seems to be in line with the results. The casual effect was only seen with body mass index (probably quite noticeable) but no other cardiometabolic health measures.

In other words, the fatter a person is, the more likely he/she is to feel less happy/satisfied with life.

obese people report lower levels of wellbeing