This subgroup of people are not much discussed. They tend to lose weight rather than gain weight so they have no adiposity problems, but they can have muscle atrophy problems. I am part of this subgroup and am interested on how to optimize my tendency to catabolism. Presently, if I leave my instinct rule over my feeding habits, I’ll lose weight very gradually, until hitting a threshold (a setpoint) which is may be too low as an optimum. So, I decided to try the very recent version of ChatGPT5.2 and submit a detailed prompt, as follows. Also, I’m reasoning that when following instinct and losing very gradually weight, this may constitute a natural substitute of Rapamacyn, since a catabolic state means the opposite of growth and proliferation.
EDIT: Probably it was not ChatGPT5.2 which answered me in the first instance. It was a little underwhelming. The answer in the next post is by ChatGPT5.2 and is much better. If the difference is due to the passage from 5.1 to 5.2, that’s a significant improvement. But sometimes strange things happen along the routers.
I just found the previous answer underwhelming. Especially in consideration of the buzz about the newest 5.2 version of ChatGPT. Now I realize my interface was stuck to the 5.1 version, or maybe there has been a recent rollover. So I asked the same question again. Now the answer is more complete, and I like the introduction. This phenotype may constitute a superpower for longevity but it may mean to walk on a razor’s edge. Very interesting. With this phenotype, priority should be to fight catabolism in muscle mass, bones, and connective tissue.
The phenotype you’re describing—older than 60, generally healthy labs, but low appetite and a baseline drift toward negative energy balance and catabolism—can be a quiet superpower for some aging pathways, and a silent risk amplifier for others. The core tension is this: many longevity-associated signals come from “perceived scarcity,” but late-life robustness depends heavily on preserving lean mass, strength, and physiologic reserve. The same biology can help one axis (metabolic/cancer risk) while harming another (frailty resilience).
Fortunately I didn’t lose my appetite for eating until after I reached age 80. My subjective feeling for this loss are, reduced sense of smell and taste, increased sense of satiation after only eating a little bit of food.
This is quite common with older people, hence the grocer shelves stocked with high protein drinks like Ensure.
A few excerpts from a rather lengthy ChatGPT report: Brain appetite signaling changes with age
Aging alters hypothalamic regulation of hunger and satiety.
Key changes
↓ Sensitivity to ghrelin (hunger hormone)
↑ Baseline leptin signaling (satiety hormone)
Blunted dopamine reward response to food
Result:
Food simply feels less rewarding and hunger signals are weaker, even when caloric needs remain.
Bottom line (important perspective)
Appetite loss in healthy older adults is not a failure of the body — it is an evolutionarily conserved metabolic adaptation.
However:
Protein needs increase
Micronutrient density becomes critical
Under-eating accelerates frailty, sarcopenia, immune decline, and cognitive loss
Practical implications (very brief)
Smaller meals, higher protein density
Strong flavors (umami, acids, spices)
Liquid calories often better tolerated
Resistance exercise restores appetite signaling
Address inflammation and oral health
Desertshores, what you underlined is interesting but it outlines a natural trend of loss of appetite with age, whereas light eaters have usually been light eaters even when younger. I sure was, barring the time when I worked out intensely, this was the only way I could boost my appetite significantly.
It may be however that this issue is exacerbated with old age and it becomes potentially a serious one.
Fortunately, I am not experiencing a lesser reward from food or loss of smell and taste, but I satiate easily neverhteless.
I can’t characterize about being a light eater when I was young except that I was never very hungary. I was on the thin side until I reached 40. I was somewhat overweight during my 60’s because my job became sedantary with little oppertunity for regular exercise. I am now on the thin side with no appetite, my current BMI is ~21.
Probably you qualify for the light eater phenotype, they are mostly lean but lack of exercise may result in an excess of calories. Now you unfortunately have the added drawback that, not appreciating fully taste and smell, are losing reward from food hence there is a tendency to eat less.
What is your present strategy to counteract an excess in catabolism? Including protein beverages, are they useful and do they result digestible enough to you?
I can share a couple of thoughts. My husband is 88 and experiencing this bigtime. I am 76 and starting to feel it as well.
There is a protein drink made by Fairlife. It comes in two formulas. We use the one that has 42 grams of protein and 230 calories. It is milk based and the protein comes from casein. The vanilla is very palatable. Two downsides: it is sweetened with asulfame potassium, and it is nearly $5 per bottle ($52 for 12 at Amazon).
The only red meat we consume is the relatively little I put into the chili I make, which has lots of beans. So have started supplementing a little leucine.
My husband has a fruit smoothie every day, and puts in some pea protein plus a “smoothie powder” concoction that I made him that contains mostly creatine monohydrate, but also some taurine, lysine, collagen,TMG. I cannot tolerate creatine monohydrate but I do microdose creatine HCL (gummies).
I think we’re holding on to our muscle pretty well, and our BMI’s are 21 (him) and 18.5 (me). I am way toward the end of the “catabolic” type, so fighting hard to keep the muscle.
I eat more things that I like, steaks, eggs, whole milk, Häagen-Dazs ice cream, fewest and best ingredients of any ice cream that I can find, cheesecake from the Cheese Cake Factory resaurant, not the store.
TASK provide an actionable scheme to keep muscle tissue, connective tissue, bones tissue and immune system fit in presence of little appetite (light-eaters) with a consequent natural tendency to ingest a calories content in the lower percentiles or less.
This constitutes a pretty thorough and sensible answer by ChatGPT5.2, I’ll paste the introduction and then the link to the whole answer.
You’re describing a real longevity bottleneck: if appetite is low, total energy and total protein tend to undershoot, and the body may “pay the bill” by slowly drawing down lean mass, tendon/ligament collagen turnover, bone remodeling balance, and immune reserve. The practical solution is usually not “eat a lot more,” but make each calorie disproportionately anabolic and micronutrient-dense, and pair it with mechanical loading so the body has a reason to allocate scarce resources to tissue maintenance.
Below is an actionable, light-eater–compatible scheme. I’ll state claims in probabilistic terms, and highlight where uncertainty is meaningful.
This thread is a discussion on the recent interview to Walter Willet in Simon hill’s podcast.
There are a few very usefuil actionable suggestions for light eaters.
1)The first one I believe is beans and legumes. Since there seems to be no decisive data on their benefits and since they are hard to digest especially so to light eaters, the actionable suggestion woudl be to include them in very limited amounts. This is what I’ve been doing, by the way. No overload on the digestive system for a food which may not live up to the claims in terms of exceptional benefits. Potentially very good for heavy eaters with powerful digestion, definitely not for the light eaters.
2)The second is nuts & seeds. Huge benefits here, including light eaters, providing the optimal threshold is chosen which maximizes input of nutrients and calories bu tkeeps the digestive loads not excessive
£)Last, dairy products. Within the subgroup of light eaters, this is one of the best choices. Usually, this phenotype has lowish IGF-1, so no risk from overshooting the growth factors, on the other way, benefits from taking it into the optimal range. Plus, high DIASS so best aminoacid profile and absorption. Always within this subgroup, those who do not tolerate dairy, can switch to soymilk, that has the highest DIAAS index in the vegetable protein foodgroup.