I’m naturally slim, used to be skinny, but now also (at 58) have the potential to develop a belly if I don’t watch out.
I agree with Wayne that “No one I know says you should not practice other forms of exercise along with your tai chi.” and also “Diet is of utmost importance.”
My tai chi practice itself, which includes form, some jibengong, staff/pole and quite a lot of fixed-step/moving-step tuishou and applications/relaxed sparring, continues to give me a great basis for using my body efficiently. I can be light/nimble/fast and ‘heavy’ simultaneously, I have pretty good proprioception and balance. Through good alignment I can let my skeleton do the work it’s supposed to do instead of using muscles to ‘hold up a wonky tower’, thus freeing up muscles for better tasks. And I have loads of fun and satisfaction with tai chi. BUT I find it necessary to do other kinds of exercise too. Aerobic exercise through cycling (but not a great deal) and through running, or if I’m having a ‘difficult knee period’ then on the elliptical cross trainer in the gym around the corner. Plus ‘Indian’ club swinging every day. My tai chi creates the physical conditions/abilities for me to engage in these other forms of exercise without significant ‘wear and tear’ or injury risk. If I don’t do these other forms of exercise, then I can feel it’s not enough for my body and metabolism as a whole. Especially because my main source of income is as a translator, hence sitting on my ass (or standing) at the computer for longer periods.
I get where Formosa Neijia is coming from, but I think he’s throwing out the baby with the bathwater a little. On the other hand, everybody is different in terms of body and mind, so whatever floats your boat...
As said, I don’t really have a big weight problem simply thanks to my genes but I can still start developing a gut (my metabolism changed again a few years ago). So now I mostly do interval fasting from evening to lunchtime, consuming only (warm) water for 12 to 14 hours a day. That has radically improved my digestion and sense of well-being. During feeding time in my enclosure I eat pretty much what I want in terms of quantity, but not excessive junk food and plenty of fruit and veg. If I don’t eat ‘enough’ then despite the upper body exercise I start to get too skinny again – for me, sarcopenia and an incipient belly are the Scylla and Charybdis between which I must steer, so getting enough carbs and protein remains important for me. But aerobic exercise too, otherwise my bad cholesterol goes up: this seems to be a genetic factor as I get older, not really due to diet.
Well, we all have to find our own course, and probably keep modifying it over the years.