Monthly Archives: September 2012

Exercise: Is Less Better Than More?

NOTE: Shou-Ching and I will be traveling in Europe next week; she’ll be speaking at this meeting and we’ll take a few days vacation. Blogging will resume on October 2 or so.

A New York Times column, “For Weight Loss, Less Exercise May Be More,” got some attention this week. It was based on a recent study of the effects of exercise on weight loss.

The Danish study [1] found that exercise is helpful for weight loss – but only the first 30 minutes of light exercise per day. Additional exercise had no effect on body weight – in fact it even seemed to diminish weight loss. Those who jogged for 60 minutes a day lost five pounds, those who jogged for 30 minutes lost seven.

The subjects wore activity tracking devices – Actigraph GT1-M devices, which are an older model of these and similar to a Fitbit – which produced a surprising result. Those who exercised 30 minutes a day were seemingly energized by their exercise, as they became more active in their daily lives – more likely to take the stairs, for instance. Those who exercised 60 minutes a day, on the other hand, seemed to be worn down by their exercise, and became less active in daily life.

It seems that 30 minutes of exercise improved health but 60 minutes of exercise may have diminished well-being. When it comes to exercise, perhaps, less is more.

A Well-Supported Result

While the Danish study [1] was novel in looking at how weight loss and non-exercise activity respond to exercise, it is not the first study to show that light activity may be healthier than intense activity.

In the new Scribner edition of our book, we greatly expand the part which discusses how to optimize immunity and heal or prevent disease. The new edition discusses exercise. We found a number of recent studies showing that light daily activity is as good or better than intense activity for health:

  • A study of American runners found that those who ran between 1 and 20 miles per week at a jogger’s pace of 10 or 11 minutes per mile reduced their risk of dying as much as those who ran more than 20 miles a week or who ran faster. [2]
  • Another Danish study reported that Danes who exercised two or three times per week for a total of one to two and a half hours reduced mortality by 44% and extended their lifespans by 6.2 years for men and 5.6 years for women. Those who exercised either more or less had less benefit. [3]
  • A study of 416,175 Taiwanese adults found that an hour and a half of moderate exercise per week (13 minutes per day) reduced mortality by 14% and extended lifespan by 3 years. An additional 15 minutes per day reduced mortality by only another 4%. Benefits peaked at 50 minutes of exercise per day. [4]

These are intriguing results. What’s more intriguing is that it doesn’t seem to matter how fit the exerciser is. People gain substantial health benefits from light exercise, even if the activity never makes them fit.

An Evolutionary Argument for Not Over-Exercising

Thanks to Stephan Guyenet, we’ve been talking a lot about the reward system of the human brain. It evolved in order to make us want to do healthy things, like braving the stings of angry bees to get honey from hives concealed high in trees.

David recently linked to an interesting post suggesting that our Paleolithic ancestors may have done a lot of honey gathering, which reminds me of this movie about the Hadza and their honey seeking:

Why did we develop an attractive taste for sugar, and why does the brain reward us for carb consumption? Presumably because the Paleolithic diet was too low in carbs for optimal health, and evolution wanted to encourage Paleolithic hunter-gatherers to gather more honey.

But, however valuable carbs are, it’s not clear that they are as valuable as the extra six years of life we obtain from light daily exercise. Yet there’s no innate reward for exercise. Many people are quite content to live their whole lives as couch potatoes.

Why didn’t evolution reward exercise, if it is as valuable as carbs? Probably because Paleolithic humans almost invariably got more exercise than they needed. Perhaps our brain evolved to prevent our ancestors from over-exercising, and now our brain unfortunately rewards us for over-resting!


It looks like exercise is healthful, but most or all of the benefits come from a relatively small amount – the first 30 minutes per day.

Doing the research for the new edition of our book has led me to revise my ideas of why exercise is beneficial, and how we should exercise to optimize health. In my next post, I’ll discuss why I think light exercise is most healthful, the tension between healthfulness and fitness, what I think a health-oriented exercise program should look like, and how my personal exercise activity has changed.


[1] Rosenkilde M et al. Body fat loss and compensatory mechanisms in response to different doses of aerobic exercise–a randomized controlled trial in overweight sedentary males. Am J Physiol Regul Integr Comp Physiol. 2012 Sep;303(6):R571-9.

[2] Gretchen Reynolds, “Moderation as the Sweet Spot for Exercise,” New York Times, June 6, 2012,

[3] European Society of Cardiology (ESC) (2012, May 3). Regular jogging shows dramatic increase in life expectancy. ScienceDaily.

[4] Wen CP et al.  Minimum amount of physical activity for reduced mortality and extended life expectancy: a prospective cohort study. Lancet. 2011 Oct 1;378(9798):1244-53.

Do the Elderly Need Paleo More than the Young?

I also do work in economics and one of my favorite economics blogs is Evolving Economics by Jason Collins. He has an interest in biology and Paleo diets and recently linked to an interesting train of thought from evolutionary biologist Michael Rose.

Here is a summary from Peter Turchin, who adopted a Paleo diet this spring after talking to Rose:

We think of people having ‘traits,’ but actually we change quite dramatically as we age. … As an extreme example, consider reproductive ability, something of great interest to evolution. Humans do not reproduce until they reach a fairly advanced age of maturation (puberty). Young adults are not very good mothers or fathers, but they improve with age during their twenties. After that reproductive ability declines and eventually disappears. …

Ability to digest certain foods can also be age-dependent. I have already mentioned the ability to digest lactose, the sugar present in milk. Before we domesticated animals such as cows and sheep, only very young humans had this ability. Natural selection turned this ability off in adults because they never needed it (and it would be wasteful to continue producing the enzyme lactase that aids in the digestion of milk sugar). …

Because abilities to do something at the age of 10, 30, 50, etc. are separate (even if correlated) traits, they evolve relatively independently of each other. When grains became a large part of the diet, the ability of children to digest them (and detoxify the chemical compounds plants put into seeds to protect them against predators such as us) became critical. If you don’t have genes to help you deal with this new diet, you don’t survive to adulthood and don’t leave descendants. In other words, evolution worked very hard to adapt the young to the new diet. On the other hand, the intensity of selection on the old (e.g., 55 years old) was much less – in large part, because most people did not live to the age of 55 until very recently. …

The striking conclusion from this argument is that older people, even those coming from populations that have practiced agriculture for millennia, may suffer adverse health effects from the agricultural diet, despite having no problems when they were younger.

This is an intriguing argument. Several aspects of it are well supported: there has been recent evolution to enable people to cope with toxic diets, and there are substantial changes in how we respond to food as we age.

Recent Genetic Evolution

We know that there has been recent evolution for greater tolerance to evolutionarily novel foods such as wheat. This is (presumably) why peoples with a long history of grain agriculture are less obese and diabetic on “western” diets than people with a long history of eating healthy foods.

The Pacific islanders are a great example. The world’s highest obesity rates are in the Pacific – for instance, in the Kosrae district of Micronesia, 88% of adults are overweight and 59% obese – yet they were notably slim sixty years ago when still eating their traditional diets. [1]

In our book, we note that the traditional diets of Pacific Islanders are almost toxin-free. A logical inference is that because they have for millennia eaten the world’s least toxic diets, Pacific Islanders never needed to evolve (or lost) an ability to cope with toxin-rich diets, and now suffer much more harm from toxic foods than do peoples whose ancestors have eaten toxic diets.

Age-Based Differences in the Biological Response to Unhealthy Food

It’s also the case that we respond to food differently as we age.

It’s not only digestion, such as the age-related decline in lactase enzyme expression, that changes. There are metabolic changes.

The elderly consume far fewer calories than the young; presumably evolution selected for minimal food utilization so that they would not be a burden to those who had to hunt and gather on their behalf. Their contribution was likely cultural, which didn’t require extensive physical activity.

Another change is that the elderly become less likely than the young to store calories in adipose tissue. This has significant consequences.

We know from a broad range of evidence that adipose tissue protects other tissues from damage by lipotoxicity; and that when adipose tissue refuses to store fat, obesogenic diets lead to metabolic syndrome and diabetes. [2] So reduced storage of calories in adipose tissue in the elderly will lead to (a) reduced rates of obesity (as measured by adipose tissue accumulation), but (b) higher rates of metabolic syndrome and diabetes.

This is exactly what we see. Here are obesity rates by age group [3]:

Obesity rates for people over age 65 are lower than for people aged 30-64.

Here are diabetes rates by age group [4]:

Despite their lower obesity rates, the elderly have higher diabetes incidence.

This difference alone is sufficient to answer the question in our title: Yes, the elderly do need a Paleo (ie healthy) diet more than the young. Diabetes is much more dangerous than adipose tissue accumulation, so the elderly will suffer greater health impairment from an obesogenic (and diabetes-genic) diet than the young.

Is There Data Specifically Testing Rose’s Idea?

Rose’s idea that an evolved tolerance for toxin-rich diets will be specific to reproductively-aged persons with agriculturalist ancestors, is, so far as I know, not easily tested by available empirical evidence.

Studies in western populations alone will not be able to test Rose’s idea, because greater intolerance of toxic diets with higher age could simply be a result of an aging process that is universal in all populations. In order to find a process that recently evolved in agriculturalists, we would have to look at rates of aging or morbidity in different populations, both western and aboriginal, and see how aging rates or disease incidence depend on dietary toxicity:

  • Are Pacific Islanders more likely than westerners on similar diets to develop diabetes at reproductive ages, but equally likely at late ages? Are they more likely to become obese at younger ages than old?
  • Is aging more rapid in traditional peoples than in westerners during reproductive years, but similarly fast during elderly years, if they eat similar diets?

I am not aware of any such studies. Let me know if you are!


[1] Cassels S. Overweight in the Pacific: links between foreign dependence, global food trade, and obesity in the Federated States of Micronesia. Global Health. 2006 Jul 11;2:10.

[2] Unger RH, Scherer PE. Gluttony, sloth and the metabolic syndrome: a roadmap to lipotoxicity. Trends Endocrinol Metab. 2010 Jun;21(6):345-52. Sun K et al. Adipose tissue remodeling and obesity. J Clin Invest. 2011 Jun;121(6):2094-101.

[3] Health, United States, 2008: With Special Feature on the Health of Young Adults. National Center for Health Statistics (US).

[4] 2011 National Diabetes Fact Sheet,

Around the Web: Back to School Edition

Greetings, everyone! It’s hard to believe our last Around the Web was all the way back on April 21. And that we’ve only managed a few days off for swimming and hiking in that time.

We’re very excited about the new Scribner edition: Perfect Health Diet: Regain Health and Lose Weight by Eating the Way You Were Meant to Eat. Can’t wait for it to come out! This version is really solid scientifically, we believe it will bring many people to better health, and we’re very excited to have the opportunity to bring PHD to a popular audience.

We want to extend our thanks once again to all the readers who have left their stories on the Reader Results page, and who gave permission for their stories to be used. Thank you! We were recently in New York to meet with the Scribner editorial staff and they said the reader stories were the best part of the book. I don’t think that was only in comparison to the parts we wrote.

[1] Prayers needed: Frequent commenter erp’s daughter and son-in-law have suffered severe burns in a small plane crash and are in critical condition. Please pray for their recovery.

[2] Podcasts: Let me recommend once again my podcast with Abel James, the Fat Burning Man: Paul Jaminet: The Perfect Health Diet, Safe Starches, and Intermittent Fasting. Abel was very well prepared, indeed he read the whole manuscript of the Scribner edition before our chat, and we covered a lot of material from the book. (By the way, Abel has a $0.99 Intro to the Paleo Diet. Can’t beat the price!)

I’ll be appearing on Cary Nosler’s Wide World of Health on Sunday September 9 at 4 pm EDT/1 pm PDT, unless baseball playoffs interfere in which case it will be at 3 pm EDT/noon PDT.

Finally, I’ve recorded an interview with Jordan Reasoner and Steve Wright of, scheduled to go live on Sept 27. Topics included the role of infections in inflammatory bowel disease, and how diet can help. Jordan and Steve have a great site for bowel disease patients. Both have been friends of the blog for quite some time; Jordan was one of our first readers and wrote one of the first Amazon reviews of our book.

[3] Music to read by:

[4] Reader Results:

Kevin Lyons started our diet two weeks ago and is live-blogging his experience at “Perfect Health Diet in Practice.” So far, so good: he’s lost 5 pounds, lowered his blood pressure, hasn’t been hungry, and “my energy and mood was great.”

Francesca has some good news about her husband:

He is 68, has a severely degenerated mitral valve and the surgeon’s opinion nine months ago was that immediate surgery was necessary. After just over a year on PHD he feels great and has no symptoms other than atrial fibrillation. He refuses to have the operation while he feels so well, has plenty of energy and is never breathless, not even when walking fast up steep hills or doing hard physical work.

He has refused all blood thinners, even baby aspirin, which infuriates his doctors…. [His] severe fatigue … has miraculously almost disappeared since going on PHD.

JonMarc Grodi has lost 50 pounds, and his wife Teresa 45 pounds.

Her complexion, body composition, energy levels, cravings/hunger, digestion, and other aspects of health have all improved. I have cut my exercise down to a fraction of what I am used to and at the same time put on a ton of muscle.

Pam has improved her cholesterol numbers and increased bone density. Ryan has improved his skin and appetite control.

A friend of Rich’s lost 35 pounds and

more importantly I feel fantastic…. Food no longer has a hold of me…. After 7 months of being on the Perfect Health Diet, my blood pressure was good. (I have always been borderline high). My bad cholesterol was good and my good cholesterol was outstanding. My triglycerides were ridiculously low.

I am now a huge advocate for this way of eating. It has changed my life, and I am excited about it.

MH has “been following PHD for 8-9 months, with wonderful results across the board.”

Marc got rid of his rosacea and stubborn body fat.

Catherine fixed her blood glucose and her headache vanished.

MsBB says “since following this diet-I have boundless energy. My yoyo hypoglycemic events have ended. Sleep like a rock.”

Daniel Han has lost over 90 pounds.

Lauren had chronic migraines for 16 years. No more!

Dr. Helen Riley has dropped a dress size and has more energy.

Steve Reichard has normalized his previously high blood pressure.

Ana Cheeseman says, “My health and energy levels have significantly improved with the PHD!!!! Thank you for sharing all this!!”

Justin: “I was diagnosed with fibromyalgia in 2009, improved on Savella, then plateaued, and now on the PHD for a few months, am improving almost back to where I was in my early 20?s.”

[5] Elsewhere on the Web:

There’s been some fractiousness in the Paleosphere while we were away. Melissa McEwen started a blog to document it: PaleoDrama. Richard Nikoley then declared war, producing but one casualty: his own sleep. Perhaps the blog should have been titled “PaleoComedy.”

Paleo is mainstream. Other evidence: the Roadkill Café is going upscale: get ready for “New Gather Cuisine.”

It’s not just Paleo: carbohydrate restriction has triumphed.

Dan’s Plan has a great infographic: Optimize Your Health.

Chris Kresser sticks to his guns: It’s OK to eat high-on-the-food-chain ocean fish despite mercury risks. ProfDrAndro of Suppversity reports on a conflicting study; Chris’s earlier article.

Nutrisclerosis by Whitney Ross Gray gives the Paleo community another MS recovery story, similar to that of Terry Wahls.

Catch-22: If you make public your cure for cancer, it’s impossible for anyone to bring it to market.

Sometimes journals are reluctant to publish negative results, which is unfortunate, as it would have deprived us of this interesting case study. (Via Greg Mankiw.)

It’s not just black cats whose paths you shouldn’t cross.

Dr Davis says “we’re seeing hundreds of thousands of people losing 30, 80, 150 pounds” by giving up wheat. Great news if true! Oddly, he doesn’t seem aware that gliadins are a component of gluten. Perhaps the journalist garbled the quote.

A good question is: If avoiding grains is so good for health, why didn’t traditional peoples discover it? Maybe they did. Via Martin Inderhaug, the ancient Chinese practice of Bigu.

Pal Jabekk advises: Jump!

Easy as Pi likes our diet.

Against my claim that starch is better than sugar, the Ray Peat Forum is soliciting rebuttals.  Andrew Kim stepped forward with “Fructose is > Glucose” and “Fructose is > Glucose Part II.”

Questions I hope I don’t get asked: Why does this woman need to be upside down? Why is this girl blue?

Caroline Lunger is a prolific young blogger. She made a common mistake – going too low carb on GAPS.

Horses do better on high-fat than high-grain diets.

Emily Willingham replies to the New York Times autism and inflammation article.

Besse Cooper has turned 116. She still doesn’t eat junk food.

Russ Crandall, The Domestic Man, has tips for easing into a Paleo diet.

The Power of Poo” is a resource for those considering fecal transplants.

Great line from Dallas and Melissa:

A Paleo way of life is about choosing to partake in a “nutrient-dense life”, complete with deeply nourishing food, emotionally satisfying social relationships, and genuine interaction with the natural (i.e. outside) world.

In a major upset, a seven year-old won the national ram-groping tournament.

The responsibilities of an academic are teaching, research and service fundraising.” Much research cannot be trusted because many academics exchange scholarly integrity for career success.

“Putting a mango directly into my mouth was stupid. I admit that.”

[6] Cute animal: NO!!!! Don’t do it doggie! It’s not Paleo!

More cute animals here. Via Craig Newmark.

[7] Not the weekly video: Cuter animals:

[8] Photo art:

[9] Weekly video: How to get the Spirit Mars Exploration Rover to Mars. Having worked on projects like this, I can tell you that many of the people in that room will have worked on this project for 20 years. A lot of one’s life hinges on that few seconds when you find out if the landing was successful!