Dear Mark: Low-Fat Beats “High-Fat”; Prunes for Bone Health

Low Fat StampsFor today’s edition of Dear Mark I’m answering a pair of great questions. First, Vaughn asks me about a recent study where ethnic Chinese participants were placed on several different diets, and those on the “low-carb, high-fat” one actually did worse than those on higher carbs and lower fat. Should you give up your low-carb approach? Then, I explore the bone-strengthening effects of prunes and discuss the Simon and Garfunkel diet.

Let’s go:

Hi Mark,

What are your thoughts on this study from China where a low-fat diet beat out a high-fat diet in healhy adults?


Interesting paper. Thanks for the tip.

It sounds damning.

Chinese adults were split into three groups, each receiving different diets. One group ate high-carb, low-fat. One ate moderate carb, moderate fat. One ate high-fat, low-carb. Protein was the same across all three groups.

After six months on their respective diets, the high-carb group had the best metabolic outcomes. They lost the most weight, the most inches off their waists, and saw the biggest improvements to their blood markers. The next best was the moderate carb/fat diet. The worst was the high-fat/low-carb diet.

Oh man, Sisson. You mean to tell me that the LCHF group subjects were eating more fat and had the worst results. That’s that. I’m out. This is all a sham.

Hold on a minute. Something in the study design caught my eye.

By replacing a proportion of energy derived from carbohydrates (white rice and wheat flour, the most consumed carbohydrate sources in China contributing to 70% and 17% total carbohydrate respectively) with fats (soybean oil, the most consumed edible oil in China rich in unsaturated fatty acids), we achieved the required distribution of fats and carbohydrates in the three diet groups, which represented macronutrient transition in the past 30 years in China.

They replaced carbs with pure soybean oil. That’s how they modified the macros—taking a little flour away and pouring an isocaloric glug of soybean oil all over everything. Anyone else feeling nauseated?

As stated, however, this intervention does reflect the dietary trends in China. It also reflects the trends in the standard American diet. Americans (and everyone else the world over) are eating far more soybean oil than ever before. From 1909 to 1999, American consumption of soybean oil rose more than 1000-fold. Yes: Those are three zeros.

But it’s not relevant to most of my readers.

Something else jumped out at me. High-fat and low-carb were actually higher-fat and lower—carb. That’s an important distinction. Relative to the other diets, folks in the third group were eat fewer carbs and more fat. Relative to the Primal eating plan, they weren’t. At 40% fat, 46% carb, they weren’t low-carb or high-fat in an absolute sense.

Forty-six percent carb isn’t low-carb by any stretch of the imagination. The results from this study probably don’t apply to someone eating 20% carbs.

All that said, I find it plausible that ethnic Chinese would have genetic adaptations to a higher carb diet. They tend to produce high levels of salivary amylase—an oral version of the digestive enzyme responsible for digesting starch—which is an indication of ancestral exposure to starch. People who make more salivary amylase have better metabolic responses to starch intake. In the context of higher-carb diets, they’re also less likely to be obese.

Maybe not, though. A 2015 paper found positive relationships between starchy carb consumption and metabolic syndrome prevalence among Chinese adults. Carbs from other sources—fruits and veggies—had no such relationshp to metabolic syndrome.

Confusing stuff, eh? There’s always some new wrinkle to explore.

JTB asked:

Mark, if you do a follow up piece, consider looking into the studies on dried plums, and perhaps also the study on the “Scarborough Fair” diet, which also showed positive bone-health results for the group using a specific set of herbs, fruits and vegetables.

You’ve got it, JTB. Everyone overlooks prunes, and I’m a big Simon and Garfunkel fan. I accept your proposal.

What’s the deal with prunes? Most people only think of them as tools to fight constipation. And, boy, do they. Prunes work so well that prune juice has become a joke. C’mon, what’s the first thing you thought of after reading the word “prunes”? Exactly.

Prunes are great for the gut, but they don’t just instigate excellent defecation. They actually promote good gut health by increasing the growth of beneficial microbes and inhibiting the growth of pathogenic microbes. They may help prevent colon cancer by acting as a prebiotic.

Animal and cell culture studies do indicate benefits to bone turnover. There are different theories as to why. Prune polyphenols are nice but probably not responsible for the effects on bone health. My guess is it’s the prebiotic effect, given that we know from last week’s post that probiotics can improve bone health.

If these effects hold in humans, and I think they will, prunes are an excellent choice. They don’t even spike blood glucose all that much, despite being dried fruit quite high in carbs. 

Now let’s look at the Scarborough Fair Diet. First, open this in a new tab and turn the volume up.

The Scarborough Fair Diet’s quite interesting. Researchers constructed it from all the fruits, vegetables, and herbs that have been shown in animal studies to improve bone health. Most were extremely high in phytochemicals. This diet was pitted against a diet containing basic fruits, vegetables and herbs. Both diets had the same amount of plant foods.

Where the Scarborough Fair Diet had parsley, sage, rosemary, thyme, and garlic, the regular diet had mint, basil, and oregano.

The SFD had prunes and oranges; the regular diet had apples and bananas.

The SFD gave bok choy, rocket, red cabbage, and lettuce; the regular diet gave spinach, silver beet, and white cabbage.

The SFD gave broccoli, onions, tomatoes, mushrooms, green beans, cucumbers, and leeks. The regular diet gave carrot, pumpkin, courgette, peas, and cauliflower.

Both contained very nutritious foods. I’m a big fan of most of them. But only the SFD improved bone turnover markers and calcium retention in postmenopausal women. That’s a very cool effect, and it suggests that the various nutrition-based bone health interventions in animal studies likely carry over into humans, too.

That’s it for me, everyone. Thanks for the great questions. Be sure to help out with your input down below or throw a few more questions my way. Always happy to help.

Take care!


TAGS:  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.

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28 thoughts on “Dear Mark: Low-Fat Beats “High-Fat”; Prunes for Bone Health”

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  1. I’ve always wondered why every official “low carb vs. low fat” study combines a minuscule change in the macronutrient ratio with some sort of industrial frankenfat. Replace the simple carbs with grass-fed tallow or pastured lard, and drop the carbs to under 20g/day and see what the results are.

    1. If by industrial frankenfat you are referring to soybean oil, it’s icky stuff and can be found in many processed foods these days, probably because it’s cheap. It has an overpowering, off-putting flavor that, IMO, gives food a slightly rancid taste. It’s the primary reason why I switched from commercial mayonnaise to making my own. Fortunately, the market hasn’t been cornered. There are now a few brands of mayo available that do not use soybean oil, such as Whole Foods 365 brand and Mark’s own Primal mayo.

    2. As somebody who just bought 5 gallons of grass fed beef tallow, I approve of this message!

      Mark, slightly off topic but could you post the title of the studies you link, at the bottom of your post or something? Inevitably somebody will bring this up to me in 9 months as a reason my diet will kill me, and it would be much easier to search for this article (and all your other wonderful reviews of studies) if the exact name was here somewhere!

  2. Sure the Low Carb diet was poor (and not that low), but the High-Carb / Low Fat diet had poor quality carbs and still did good. Food for thoughts.
    By the way, carbs don’t make you obese. Constant overeating does (be it high carbs or high fat).

    1. So far as I know, nobody here is saying that eating too much, be it carbs or fat, doesn’t make you gain weight. However, a diet high in decent fats (NOT seed oils), low in carbs, and moderate in protein, tends to naturally decrease caloric intake without counting calories and measuring everything. Partially because fats take longer to digest, thus making one feel full longer. Additionally, a diet high in carbs tends to make one reliant on glycogen (glucose) for energy, and poor at burning fat for energy. Since you can only store a finite amount of glycogen at any given time, people on a high carb diet tend to need to eat more often, thus making it harder to decrease caloric intake. People on a high fat, low carb diet tend to be much more efficient at using fat for energy.

      1. This:
        ” In the context of higher-carb diets, they’re also less likely to be obese.”
        Kind of insinuated that high carb diets make ou obese 😉

        1. That’s because most people, on a high carb diet, will end up obese. There are exceptions, which I will get to later. For most people, my comments above do a decent job of explaining the basics of why a high carb diet is not the best for weight control. Also add in the fact that different foods affect people’s metabolisms, hormones, and what not, differently. I saw a study a while back where people were randomly assigned to two groups. Both increased their daily caloric intake by the same amount for a set period, I think it was a couple of months. Anyway, one groups increased calories came from peanuts, the other’s from hard candy. If calories were all that mattered, both groups would be expected to gain about the same amount of weight and have the about same increase in waist measurement, right? But that’s not what happened. The hard candy group gained more weight and more inches around their waists than the peanut group.

          Now some people do have genetic adaptations that allow them to do quite well on a high carb diet, but they are few and far between. Others are active enough that they can handle the carbs.

          If you want to learn more about this, go to the top of the screen, click “Home,” scroll down to “What Is the Primal Blueprint?” click “Explore” and then start reading topics. Another useful site is Peter Attia’s The Eating Academy.

          1. I talk about carbs, you talk about candies…
            High carb diet (ideally good carbs), as long as you are not overfeeding, will not get you fat.
            Body composition or whatever is not the subject, it is just the shortcut “high carb => obese” that is wrong.

          2. While that is an extreme example, it does illustrate that, at least in some cases, the types of calories matter, that it’s not just a simple matter of controlling caloric intake. Also, the statement you initially referenced does imply that eating a high carb diet makes people obese, but not everyone – you know “less likely.” As I said, many people are obese on a high carb diet and that is partially because a high carb diet makes it harder to keep your caloric intake down.

            You may want to peruse some of the success stories, in this site. I know I’ve seen people say that they’re eating more, more food and more calories following the Primal Blueprint, and were losing weight. But some people can handle hig carb, most can’t.

  3. Yeah, 46% carbs is high, and not a carb-controlled diet by any stretch.

    If I’m on 2,000 calories per day, and 46% of my intake is carbs, that’s 920 calories from carbs. There are approx. four calories in a carb so we have 920 / 4 = 230 carbs.

    Combine that with 88 grams of fat (2000 * .4 / 9) and you have the classic gotcha of sugar + fat = trouble.

  4. Prunes – meh…. I can handle dried pluots, but not really prunes, for whatever reason.

    BUT… plums are one of my favorite fruits – I wonder if they are just as good?

  5. “They tend to produce high levels of salivary amylase—an oral version of the digestive enzyme responsible for digesting starch”
    While living in China, I never got why the spitting thing is so extravagant here. Knowing this,it gives a whole new meaning.

  6. I’m Chinese and more and more of my Chinese friends and family are starting to lower their carb intake with the uptick of obesity and diabetes in Asia and in their own families; I think it’s a misconception that Chinese people eat tons of carbs; the more health-conscious ones may only eat 1/4 cup of cooked rice with a meal full of vegetables and protein. Some like myself just don’t eat much rice anymore, and very little wheat-based food, which is foreign to China anyway (white flour was not a normal ingredient and for a long time was expensive). For myself, starting in high school, even though I was active with school sports, I didn’t lean out until I reduced my rice intake.

  7. Mark, I love how you do the detective work for us on these controversial studies. Your blog is such a fantastic wealth of information. Thank you!

  8. Would love to see a similar study but replacing the flour with more natural sources of fat (coconut oil, lard, etc.)

  9. Prunes have actually been PROVEN to improve bone mineral density (BMD) in humans (postmenopausal women to be exact).
    The researchers gave 100 grams (3.6oz) of prunes to half of the participants and dried apples to the other half. Both groups received the same amount of supplemental calcium (500mg) and Vitamin D (400IU). Prines “significantly increased BMD of ulna and spine in comparison with dried apple. In comparison with corresponding baseline values, only dried plum significantly decreased serum levels of bone turnover markers including bone-specific alkaline phosphatase and tartrate-resistant acid phosphatase-5b. The findings of the present study confirmed the ability of dried plum in improving BMD in postmenopausal women in part due to suppressing the rate of bone turnover.”

  10. It appears that JBT is asking about dried plums, and Mark is answering with a discussion on dried prunes. Is this just a typo?

  11. The dried plums at my supermarket and preserved with potassium sorbate – do the health benefits outweigh the any negative effects from this preservative?

    1. If prunes are the only food in your diet preserved with potassium sorbate, you’re almost certainly safe. If you consumed a lot of preservative-laden food, your intake *might* become too high, but this is unlikely on a Primal diet.

    2. I agree with the Zoltan.
      You may follow him for a month for this. If you found it good then apply it in your daily life or then you can leave it too.