Over time our bodies store more bodyfat in the abdominal cavity. This is the #1 reason why age is important in calculating bodyfat %. Additionally, it may not be as desirable for older women to be as lean as younger women, as leanness (technically, the hormonal environment associated with leanness, and what it takes to maintain it) can affect bone density.

Nevertheless, the exact % doesn’t really matter as much as how you feel and perform. The number attached to the % is just a way of expressing a physical state where you have lots of good lean mass, and enough — but not too much — fat mass to support your overall health and athletic performance. We can’t really know what an ideal weight nor % is for a given person; we can only speculate and make informed guesses. We do want people to retain as much lean mass as possible; good nutrition and training just helps keep that valuable lean mass on you (and if we’re really lucky, helps you build a little more lean mass) as fat goes away.

Throughout your fitness journey and life, your goals will probably change. Use an iterative process where you use evidence of health indicators and athletic performance to evaluate your progress and goals as you go along. If you get to 200 lbs and feel great at whatever bodyfat % that is, then awesome. If you feel good but want to keep on truckin’ with fat loss, then that’s cool too.

When I was in my early 30′s I was a runner, fit and weighed 165 lbs (size 8 then vs. size 20 now), so if I compare those numbers with my goal numbers set by my trainer, there’s a 40 lb difference. This seems inaccurate to me.

So my question is around how our bodies change over time as we age.

May I humbly suggest that you change the word “gender” in the first sentence under “body fat norms” to sex–I’m pretty certain that that is what you mean (in most common usage, sex=biologically male or female, gender=male- or female-identified).

I knew I’d be able to find the answer here, though. Thanks!