And it takes regular weight-bearing of some kind (just even active chores like farmwork and mobile lifting during grocery shopping - or intentional weight lifting!) to build and maintain dense extra muscle mass as we age. These days, many relatively privileged folks are prioritizing a lot of time in La-Z-Boy chairs watching TV…
After age 30, you begin to lose as much as 3% to 6% per decade. This loss of muscle affects balance, gait and the ability to do daily tasks. Usually, only 3/4 of midlife muscle mass remains after the age of 80.
Interestingly, rates of sarcopenia are nearly 4 times higher among high-risk drinkers than among low-risk drinkers. High-risk drinking is defined as frequent and significant alcohol use, along with a lack of control over drinking, blackouts and injuries related to drinking (alcohol abuse, in other words). This means that sarcopenia may start even in the 20s and 30s in alcoholics.
It’s interesting that muscle loss is variable in people - for example, one South Korean study determined that only 8% of 62 year old postmenopausal women had muscle loss… maybe it was because South Korea food culture involves microbiome-enhancing kimchi (and strong digestion thereby) and lots of stir fried and BBQ meat intake? Or maybe it’s because muscle loss (as well as bone loss) is assumed to be rampant when in fact it’s not when there are certain factors like a more LCHF dietary culture OR bodybuilding OR both.
Fred Hahn (Slow Burn bodybuilding expert and LCHF advocate) along with others says that 99% of muscle mass is dietary! So, it’s conceivable that the 1% that is some kind of regular weight-bearing mobility (many adults in Asian and African and Latin American cultures where there are more closeknit families carry their hefty kids grandkids in-arms or on their backs) is what creates the tone that ultimately protects the joints in the elder years.
What’s promoted in the U.S. and U.K. is a lot of scare-driven and profit-driven testing of bone mass along with prescribed medications including hormones. And the fact that both muscle and bone density loss are mostly about diet and physical strength maintenance is quite downplayed.
What I’ve read Phinney as well as Hahn advise is to not worry about exercise (esp weight-bearing for the non-athletes) until established in LCHF and feeling relaxed about everything - because cortisol from stress levels actually interferes with progress in bodybuilding.
Interesting article here from Harvard Men’s Health about muscle mass and aging which also talks up protein and progressive resistance training (though doesn’t promote the amazing slow form with minimal reps): https://www.health.harvard.edu/staying-healthy/preserve-your-muscle-mass