Two references I've recently ran across seem to say two completely opposite things about aging, or rather managing and reducing the rate of aging. Both relate to one particular input, to adjusting protein consumption and amount of bodily muscle tissue. Offsetting aging is an aggressive goal, but whether that's practical or not it can be interesting to hear about potential approaches, or even uncertain background.
One set of statements and claims by Leo (Laith) of the Leo and Longevity YouTube channel claims that reduced calorie intake, and specifically reduced protein intake, increases lifespan. Another article connects lack of muscle with aging issues, and claims that substantial protein intake is necessary to maintain higher levels of muscle tissue, which increases both longevity and health in later life. I think we can unpack both and resolve this apparent contradiction, to some limited extent.
A lot of this will be my own speculation, to be clear, and I'm not some sort of medical professional. I will mention some unusual personal exposure along the way, but that's not intended as clearly defined evidence, just extra anecdotal input.
So there we have it; per this longer set of conclusions losing core strength and functional muscle tissue causes lots of other health problems, which can all be avoided by weight training and eating enough protein. The part about core strength limiting risk from falls is familiar enough, but the rest not so much. I don't want to include too many tangents but this reminds me of an interesting Instagram channel, that relates to how to control glucose spikes in the body, the Glucose Goddess channel:
You probably get the idea; you can adjust what you eat together to prevent blood sugar spikes. Which are obviously a bad thing, right? Sort of, or probably, but part of what I'm interpreting that last long cited passage to mean is that with substantial muscle tissue in your body you can store that glucose better, to use it throughout the day, while if you have very little muscle tissue it's going to potentially be more impactful having that sudden digestion input fall a bit out of balance.
It could've been clearer that muscle tissue actually helps with storing glucose, since one read is that muscles burn more energy, in the statement "muscles help us control our glucose levels, use glucose as fuel, and have a role in insulin resistance." I think I've drawn that from other background, like this statement by the Cleveland Clinic:
Glycogen is a form of glucose, a main source of energy that your body stores primarily in your liver and muscles... Your body mainly stores glycogen in your liver and skeletal muscles (the muscles attached to your bones and tendons), with small amounts in your brain.
So with very little muscle tissue your body will either need to work through a blood sugar spike or else convert that energy to fat to do something with it, but muscle lets you store more for medium term use. Moving on, Leo asserts something else, in the video Protein: the Key to Longevity, and related to two other follow-up videos in a three part set.
Based on different starting points and evidence, Leo rejects the common "building blocks" model of analyzing dietary inputs, that your body uses proteins, carbohydrates, and fats as energy sources and tissue building inputs (which is certainly correct, but it's only one part of what's going on). He claims that this model is one partly accurate and descriptive construct, but not the only valid frame of reference.
At a finer level of internal body process review signaling models apply, that what you ingest triggers specific physiological processes that can be active or inactive, or partially active, not all relating to only energy use or storing fat energy. Even his complete video, that I'm summarizing here, clearly states he isn't unpacking a large proportion of this background, and narrowing related body processes down to two examples, versus treating how a larger range of them interrelate and apply.
Leo is citing a lot of well known references to low calorie intake being associated with longer lifespan, with links in that video--that part is already familiar to many. It's very problematic for people to restrict their calorie intake for extended periods of time, for years, so attempts at "dietary restriction" take other practical forms today, including intermittent fasting.
Leo goes further, claiming that lower protein intake alone can have the same effect, lengthening lifespan, especially related to limiting high levels of specific amino acids (protein building blocks), most specifically two related to red meat consumption, present at far lower levels in vegetarian proteins. This isn't a guess based on his own reasoning; he is citing the same kind of documented, peer-reviewed animal studies that initiated these earlier conclusions related to calorie restrictions, in studies conducted on fish and rodents.
If the two references are saying opposite things, and the first is based on direct input from a longevity research professional, and the second is based on many seemingly sound research sources, who can we trust? Can both be right? Maybe. I'll not fully unpack or resolve this, but it's possible that the contradiction is only apparent. I'll get to that part, but first I wanted to raise one more anecdotal input, about not personally experiencing aging as much as I expected. It does connect, and some works as a good framework of ideas for how this might play out in actual application.
A personal account of atypical aging experience
I'm 54 and in pretty good shape. Good diet and some exercise can account for that, or good genetics and luck. But my hair isn't greying much more than in my 20s, my skin isn't wrinkling much, I'm retaining more muscle mass than I think I need, but then maybe that is useful after all, given some of this input.
I suspect that staying active accounts for a lot of it (I run), but it also seems possible that spending 17 years as a vegetarian helped by keeping my body weight moderate, or even low. For early adulthood, teens out to close to 40, I weighed about 145 pounds (65 kg) at 5' 8" (170 cm), and I've only recently increased that to 165 pounds / 74 kg. I wasn't trying to be thin, or to not eat much, it just worked out that way.
That diet may have led to moderate protein intake over a long time period, and the distribution of amino acids from vegetarian sources would be slightly different (something Leo addressed specifically, best reviewed by watching that video). Even now I eat a lot of fruits and vegetables, and a generally clean diet, and need to work on it to include enough protein to support exercise recovery, from the running.
Genetics is surely a main input; my mother aged somewhat slowly, and my sister also does. It's probably not a coincidence that both maintained low body weights for their entire lives. I suspect that eating a very good diet comes into play, along with getting some exercise, or other activity, moderating input of drugs and alcohol, getting enough sleep, and so on, general healthy living.
That first article seems to waive off body weight and fat level as most relevant (or more clearly seeing that as an outcome, not a cause). Maybe it's all relevant, activity level, muscle development, amount of body weight, and positive diet inputs, nutrient levels and on from there. The modern reductionist tendency for people to look for one key cause is probably misguided, one independent "life-hack" to adjust complex inputs towards a different result by making one or two simple adjustments.
It's even more indirect and hearsay based, but it's a commonly expressed theme in bodybuilding circles that maintaining high body weight from either fat or muscle tissue adds stress to the body, and could impact longevity and long term health. Of course that's not to be wrongly regarded as directly opposing the initial point that maintaining healthy muscle tissue levels contradicts this view, that carrying excess muscle tissue is a problem. Higher level male bodybuilders can maintain moderate body fat levels while weighing between 250 and 300 pounds, with female bodybuilders typically not matching that atypical body size, which would be stressful for bodily systems. Of course intake of drugs enabling that form of growth is a secondary risk factor; no one is "naturally" gaining that kind of muscle tissue weight, and steroids and growth hormone use pose other risks.
All this isn't to speculate that we should just be healthy; that would be an oversimplification. Retaining a typical younger-life, high activity level of both fitness and muscle tissue probably are healthy. Leo wasn't claiming that carrying any level of muscle tissue is a problem; he was pointing out that internal physiological processes are "turned on or turned off" when signaled by protein intake, and other factors. He was seeing an indirect outcome from higher protein intake as a problem. Let's consider further one such process, the main one he was discussing, from a Google search results reference, on MTOR:
Mammalian target of rapamycin (mTOR) regulates cell proliferation, autophagy, and apoptosis by participating in multiple signaling pathways in the body. Studies have shown that the mTOR signaling pathway is also associated with cancer, arthritis, insulin resistance, osteoporosis, and other diseases. The mTOR signaling pathway, which is often activated in tumors, not only regulates gene transcription and protein synthesis to regulate cell proliferation and immune cell differentiation but also plays an important role in tumor metabolism. Therefore, the mTOR signaling pathway is a hot target in anti-tumor therapy research. In recent years, a variety of newly discovered mTOR inhibitors have entered clinical studies, and a variety of drugs have been proven to have high activity in combination with mTOR inhibitors.
It sounds like this MTOR is a bad thing, and we should stop doing that, but it's not nearly that simple. It's a key bodily function (internal process), that is required, so the concern here is how often or how long it is "turned on" or active, and the positive and negative effects of maintaining a greater frequency or duration of that internal process (or set of those; it's all not completely clear). Let's simplify that down a little from a Wikipedia reference:
mTOR integrates the input from upstream pathways, including insulin, growth factors (such as IGF-1 and IGF-2), and amino acids. mTOR also senses cellular nutrient, oxygen, and energy levels. The mTOR pathway is a central regulator of mammalian metabolism and physiology, with important roles in the function of tissues including liver, muscle, white and brown adipose tissue, and the brain, and is dysregulated in human diseases, such as diabetes, obesity, depression, and certain cancers.
Sounds more positive there, but none of this lends itself to simple interpretation. As Leo summarized it you can't prevent the mTOR signaling pathway (if I'm using that term correctly), but as he frames it you can help your body regulate how often and to what degree this is active. He feels that it would be a good thing to do so, and consistently eating a lot of protein throughout the day could actually be very unhealthy. It's my impression that he's linking general and broad studies that claim that, that higher protein intake levels in animals (fish and rodents, I think it was) correlate with reduced lifespans, and then he's trying to work back to why that would be, even though maybe this isn't a clear and singular cause. Personally it's hard for me to completely accept any simple conclusions distilled from complex inputs; it's back to this being more interesting to consider than relating to obviously correct conclusions.
Per my impression of that first long cited passage they are discussing problems with loss of normal levels of muscle tissue, not necessarily related to people being on a spectrum of having more or less. Exercise inputs, genetics, and those dietary inputs (eating enough or a surplus of protein) would relate to gaining and retaining muscle mass, instead of there being one main input.
Per a common sense interpretation if someone spent a period of years weightlifting to build strength, and muscle mass, and coupled that with a higher than average and high protein diet, this wouldn't be as impactful as spending a much longer time on a primarily carnivorous diet, or even an all-meat diet (a recent health trend, an offshoot of the "keto" fad). Of course maintaining normal but significant amounts of muscle tissue on a moderate protein intake diet is possible.
This reminded me of how an athlete like Alex Honnold might see this issue, a vegetarian rock climber famous for free soloing El Capitan. His take:
Humans definitely need protein to maintain muscle mass and be healthy, and athletes certainly need more than sedentary people. But I think that protein is wildly over-emphasized. The average person, in the U.S. anyway, eats far more than they need.
There's evidence that humans have optimum health with a diet around 10-percent protein - that's easily met by just eating greens like spinach. So, it's not like a typical American needs to be seeking out more protein. That said, proteins and fats do help me feel fuller so I do think about the macronutrient breakdown of what I'm eating.
The part about getting enough protein from spinach is a bit striking, isn't it? In a GQ article his typical daily diet does sound like something no normal person could live on, never mind a high level athlete, with nothing in it including a substantial amount of protein:
Breakfast: Muesli with flax meal, banana, hemp milk.
On-the-wall snacks: Apples, nuts, avocado sandwich (fresh avocado on bread)
Dinner: Macaroni and cheese with spinach, red peppers and yellow squash, topped with pumpkin seeds.
An average person living on fruit, nuts, vegetables, and granola wouldn't be that impressive, but his feat of athleticism, skill, and mental focus in that one free solo feat is all but unmatched across all of sports, pulled off on a diet most people think couldn't sustain them, whether they exercise or not.
One thing I didn't mention about my own experiences (with a very limited protein-input vegetarian diet) was that I was snowboarding and hiking a lot back then, living in a ski resort, and working long hours in demanding jobs as a restaurant server. I even rock climbed a little. I wasn't giving it much thought but in retrospect it's odd how it all worked out, even though none of that is impressive at all compared to high level rock climbing, or any competitive professional sports.
sometime in the 90s, out doing 15+ mile daily desert hikes for fun
last week; I am aging, just not so quickly for mid-50s
It makes you wonder how hormone replacement might factor in, but that's too complicated and involved to pair with these other completely separate concerns. I suspect that maintaining a high activity level sustains adequate hormone balance, even into advanced age, but what do I know.
I've known plenty of earlier generation family members who were very active and healthy, some into their 90s, but isolated cases like that aren't necessarily helpful for establishing generalities. Those old-school, rural-life family members ate from gardens more than markets or grocery stores, and my family hunted as much meat as they bought, but again I'm not reducing that to claims here. I think that eating a diverse and balanced diet is important, for me ideally including plenty of fresh fruits and vegetables, and then we can place input like these two sets of claims however we like within or beyond that.
Post script: Leo Rex of Leo and Longevity died not so long ago (Laith really; Leo is an adopted name), and it seems appropriate to mention that here. It's quite sad, to me, because in one sense it wasn't his time yet, as someone so young, bright, charismatic, and eager to help others.
Related to his sharing of information online critiques sometimes came up, that he was too eager to experiment with risky "bio-hacking" themes, and offer information that others might base their own unsafe practices on. This summarized topic example isn't that; eating a lot of protein, or very little of it, surely wouldn't pose or reduce health risks much in comparison with adjusting sleep cycles, using nootropics (mental enhancement drugs), steroids, or using other experimental exercise recovery support drugs.
I have greatly valued Leo's content and input, and wish to honor his contributions by remembering him positively here. He was a fellow seeker, that many would recognize aspects of in themselves. Sometimes even the parts that could be negative in some ways, the intensity and focus on shifting topics, and good intentions at times extended towards obsession, or pursuing a search for truth on to involving personal conflict. Rest in peace, friend.