seems to be a hot topic
probably because of the number of us having to sit in front of a screen for our day jobs
anyhoo
BMI is p flawed if you are tall
Body Adipose Index might be more useful but needs further study to see if it lines up with predictions of morbidity.
but in the end it is very simple
calories in < calories out to lose weight
better to increase your output and find a way to break the "cycle of sitting"
I got an australian shepherd dog (laid back collie) that needs walked twice a day, that and not eating my "bliss point treat" in the weekend evenings got me from 112kg to 90kg and a 38" waist to a 34" in about 12 months.
I now combine it with some really simple core exercises that i can do in front of the TV at night and swimming lengths when the kids are getting their swimming lessons rather than sitting in the cafe.
I would really like a standing desk + a low speed treadmill.
The faecal transplant stuff is another expression of the "there must be a way of solving this that doesn't involve me actually doing anything"
Your gut flora changes significantly with any alteration in diet (why wouldnt it) and the only studies done in humans were based on torturing one guy in Japan.
-good treament for C. Diff. infection though
And finally
As the HSE statistics say the above in the OP then they (like many many many national statistics) are frighteningly wrong.
cf 100% self-reported handwashing compliance statistics in the NHS along with a concomitant explosion in nosocomial infection due in a large part to poor handwashing.
The pressure for people to underreport has increased with time as it becomes less acceptable to be overweight.
Better to look at something less open to bias like type 2 diabetes rates/alzheimer's/heart disease (increasing against a background of smoking numbers going down) etc