Dear Mark: Is a High-Carb, Low-Protein Diet Best for Longevity?

dear mark longevity in lineFor today’s Dear Mark, I’m answering a question about the optimal diet for longevity. An article sent in by a reader claims that a recent mouse study has identified the perfect diet for everyone, but especially for older people: a high-carb, low-protein one. They even manage to throw in some stuff maligning the paleo diet (they just can’t resist).

Find out below if the claim holds water. Let’s go:

Hey Mark,

What’s your take on this new study claiming that the best diet for longevity is a high-carb, low-protein one?

Interesting paper. Here’s how it went:

Researchers placed mice on a bunch of different diets to see how they’d affect levels of fibroblast growth factor 21, or FGF21. The 25 diets ranged from 5-60% protein and 5-75% fat or carbohydrate. They tried pretty much every permutation and found that the low-protein, high-carb combo produced the greatest increase in FGF21.

Why FGF21?

FGF21 “plays a role” in longevity, immune and metabolic health, energy metabolism, and appetite. Implicit in the study’s aims is that higher FGF21 is a good thing. It helps us live longer and healthier. If all that’s true, of course we’d want to find the macronutrient ratio that increases FGF21 most.

FGF21 is ultimately a marker of mitochondrial stress (PDF). By doing things that boost FGF21—which include fasting, low-calorie diets, low-carb/high-fat diets, and even acute exercise—we are applying a moderate amount of stress to our mitochondria. This is a good thing, provided the fasting doesn’t lapse into starvation, the diets don’t become chronic deprivation diets, and you allow sufficient recovery from the exercise. It’s hormesis: apply a stressor and bounce back stronger than before.

And sure enough, FGF21 does some good things, like helping us transition into ketosis and improves glucose control. Researchers are even exploring it as treatment for various metabolic disorders, obesity, and diabetes.

With most hormetic stressors, the benefits turn into negatives if the exposure persists or accumulates. There’s the chance of getting too much of a bad thing.

Is there any evidence of too much FGF21 being bad for us?

  • Among Chinese males, those with the highest FGF21 levels are more likely to have a heart attack and to have another within 30 days of the last one.
  • Both the highest and lowest FGF21 levels are associated with an increased risk of cardiovascular disease and death from heart attack.
  • Higher levels of FGF21 are linked to fatty liver, cardiovascular disease, and other metabolic disorders.
  • Independent of other risk factors, high serum FGF21 predicts the severity of atherosclerosis.

FGF21 may not be causing these things, but its elevated presence is at least a marker of something bad going on.

What does this all mean?

We have human evidence that various FGF21 genetic variants can help determine how well a person does on high-carb diets and low-carb diets. Those with the C variant lost more weight, waist circumference, and body fat on a high carb diet and less on the low-carb diet. Meanwhile—and this wasn’t reported in the study abstract—those with the T variant lost more weight, body fat, and waist circumference on the low-carb diet and were still losing body fat after two years.

I guess what I’m saying is this: Go with the diet that works for you.

Losing body fat on a diet? Keep it up.

Feel good? Keep eating the way you’re eating.

Don’t eat constantly—get hungry in between meals.

Fast if you can handle it. Men may be better at it than women.

Exercise on a regular basis.

All these things will increase FGF21 in the manner that’s likely to be healthiest without getting into excessive, chronic elevation.

What about the original article’s contention that older people should eat high-carb, low-protein diets to stave off death?


We know that in older individuals, a higher protein intake is healthiest because as we age, we get less efficient at processing protein. We need more protein. Research shows that more protein promotes all the things we need to remain healthy and functional as the years accumulate.

Seniors who eat a half pound of red meat each day enjoy better physical function, get stronger, and build more lean muscle mass. That lean mass becomes ever more important the older we get. It’s a reserve for illness, injury, and bedrest. It keeps us spry and vibrant. It makes us strong; strong enough to take care of ourselves and actually engage with the outside world.

More protein (via red meat) also improves cognitive function in older adults. If you can’t use your brain, a long life gets a whole less enjoyable.

Seniors need higher protein intakes to maintain ever-critical bone density. A fractured hip is terrible for longevity.

I’ll have more to say about diet and longevity later. Bur for now, don’t tell Grandpa to ditch the protein and start slamming carbs.

That’s it for this week, folks. Take care and be sure to leave a comment down below!

Primal Kitchen Dijon Mustard

TAGS:  Aging, dear mark

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

If you'd like to add an avatar to all of your comments click here!

26 thoughts on “Dear Mark: Is a High-Carb, Low-Protein Diet Best for Longevity?”

Leave a Reply

Your email address will not be published. Required fields are marked *

  1. Well, even if some people with the C variant lost more weight on the high-carb diet, i guess the low-carb, high-fat way would still be better, because you could enjoy all the other benefits of being a fat-burning beast besides losing weight, like reduced hunger and less oxidative stress, right?

    1. I’ve done all sorts of diets in my day, including a brief stint as a vegetarian. The weight creep continued until I learned about the “caveman” way of eating–even before it was labeled as Paleo. I got rid of the sugar and the grain products and lost weight effortlessly without counting calories. There are probably people who don’t do well on a Paleo diet, but for many–maybe even most of us–it just comes naturally. I feel good on red meat and eat it at least several times a week. I also eat a lot of veggies, eggs, nuts, and fruit. (80/20 to 90/10 works well for me.) I can’t believe there are still people out there pushing high carb when it has done nothing but make the general population fat and unhealthy.

  2. “Is a High-Carb, Low-Protein Diet Best for Longevity?”

    follow-up questions:

    “Should I spray insecticides on my organic produce prior to eating them?”
    “I’m fatigued all the time, should I sleep two hours less each night?”
    “I’ve never weight lifted before, should I start out trying to squat 400 pounds?”

  3. I’ve always wondered about these studies involving mice as human analogs. I’m sure the studies have value in their own way but they are rodents adapted to a diet high in seeds and other plant matter. Is it fair to say that what happens in a mouse’s body when it eats a diet high in carbohydrates may not be all that applicable to what would happen in the bodies of bipedal, hunting and gathering primates when exposed to such a diet? Just a thought.

  4. When we get older, we lose some of our liver’s ability to process at the speed of our younger selves–as a result, blood sugars get out of whack, and we’re setting ourselves up for heart disease, Alzheimer’s, and diabetes in later years. Eating high-carb in this stage of life only speeds up this process.

    That’s the time to slow down the carb intake (if not eliminate it completely).

    Dr. Rosedale says that lowering the protein helps reduce mTor, which is key in longevity–so it’s Mark vs. Dr. Rosedale as far as protein goes.

    1. Point well taken, but I’d like to see more info. on how healthy people are with a reduced mTor. Longevity and health can be two different things. I think we already live in that world, where a lot of people are zombies the last 10-15 years of their lives.

      1. Longevity and being healthy are not separated issues. You have to understand that people living long are on average more healthy. There are no such thing as extremely sick supercentenarians.

  5. You should address Dr. Ron Rosedale’s stance on all of this. He advocates a very low carbohydrate, low protein (50-60 grams a day), high-fat diet for longevity. Even though I love my protein, his arguments are pretty convincing.

  6. I realize the economic reasons mice are used in these studies, but how can these results be extrapolated to humans at all? A paleo diet for mice IS a high carb diet!
    What it means to “eat Paleo” differs by species. Even among humans, ancestral origin probably has some affect on what “paleo” macronutrient profile works best for any given individual.

  7. My grandma does terribly on no protein. She likes to be independent but the only meals she can cook herself are microwaved pasta nastiness, canned soup or toast. When she refuses to eat our food and eats that she has her worst days, her dementia is markedly increased, she looks out of it and falls asleep. When I encourage her to eat our food-Primal, so low carb, higher protein-she is so much better, it’s crazy how fast it improves her cognitive function and even her mood.

    1. I notice this for myself when I went from a vegetarian diet to more animal fats. I could keep my concentration at work and not zone out. More awake in the morning drive to work, and less drowsy driving home.

  8. I’d like to see Mark address a similar argument but one based on the ‘blue zones’ – that some of the world’s longest-lived people subsist on high carb low protein (or at least animal product). While I’m all for plant-heavy diets (depending on the brand I regularly down a 3-pack of romaine lettuce heads amongst other things daily), I find without including a substantial animal food intake as well I’m constantly hungry.

  9. Thank you for debunking this study on mice. Anecdotally in my work with okder adults I’ve noticed that many older adults tend to gravitate towards a higher carb diet which is detrimental to their overall health. Mouth health might be a meaningful factor in this as red meat tends to be tougher to chew. My clinical observations confirm that increasing protein intake and moderate or low carb rates help maintain muscle and bone health and subsequently preserve mobility and independence.

  10. Mouse studies are interesting, but they are a long way off from being as relevant as studies using humans.

  11. I read that athletes wanting to gain muscle should eat l to 1.6 grams of protein per kilogram of bodyweight, far less than so called fitness standards. This makes a lot more sense. So wouldn’t a diet of fruit, veggies, and tublers with a little meat be optimal?

    1. Assuming an athlete of 80 kg(180 lbs) that would be about 130 gramms of protein. So that “little” meat would equal 1 pound of meat plus 4 eggs…

  12. What a lovely story! The story in this YouTube video that is posted here is in fact a fastidious one with having fastidious picture quality.

  13. I may be brainwashed but i could never wrap my head around the idea of eating more carbs than protein!! 😐 I just feel like I would be taking in too much sugar.

  14. Since November I have been enjoying a low card, high protein diet. In the past I have always been hungry and overweight. Now I’m losing weight (people are noticing) and not hungry. I don’t crave sweet things (I miss bananas but not painfully so) and I am sleeping better and generally feeling very good. I am 75 I intend to live until well over 100 with my brain intact.

  15. You can use high protein diet if you like muscles. It might be easier control feeling of hunger with protein?

    Unfortunately several research evidence shows that high protein diet is connected to shorter lives.

    Longevity diet is mostly vegetarian and protein comes from fish. It might not be body builders diet but is healthy. None of the extremely long lived communities existing nowadays have diet rich in protein or animal fats.

    You will likely have shorter life if you have diet rich in protein.