Mindset is what it takes.
Speaking with Ms DR this morning, I confess to working on the principal of I have paid for it so I am eating it. (Mess food due to unaccompanied service) whereas when at home I eat very little balanced by quality restaurant visits once or twice a week. I have been home now for 2 weeks, done a little gardening, driven the hoover around as DCoS is working, done no formal phys whatsoever, and have noticeably lost weight.
Unless it is all that exercise I am getting that remains behind closed doors!!
Seriously, the well known fact that guys who can run ragged around a rugby field yet cannot pass a RAFMSFT demonstrate that weight and fitness (and I believe the two are directly linked) is a balance of lifestyle, calories, and moderate exercise. For me running is very boring, yet lugging a camera bag miles along a river footpath at a sedentary pace on a warm day is fantastic and has its rewards in quality photographs when opportunities are exploited. I used to cycle a lot as a teenager accompanied by a guy who had just left the service after 22 years aged 40. That was enjoyable at that time. As reluctant as I am to admit it though, a 45 min gym session in the morning a few times a week to maintain RAFMSFT currency does set you up nicely for the day; just dont tell anyone I said so!! Once that facility is removed (retirement), I will rely upon prime time in the countryside to maintain fitness, and if that includes the occasional pub lunch then so much the better.