Fructose, Hunger, and Inactivity – Leptin and Insulin


I watched a video last night posted by the Ancestral Health Symposium about fructose, fat storage, and energy expenditure. Even if you’re not struggling with obesity, I think there is a lot to glean from Dr. Lustig’s research on fructose. He is an MD who did “six years at Rockerfeller – 3 in the laboratory of biochemical endocrinology and 3 in the laboratory of neurobiology and behavior.”

“The Trouble With Fructose: A Darwinian Perspective” by Robert Lustig, MD

Some of my notes follow. This really isn’t an article. It’s a collection of points I jotted down while listening.

“One reason the low carb diet works so well for most people is because it lowers your insulin.”

“Insulin makes you feel like crap.” Keeping your insulin levels low will actually result in higher energy, less carb cravings, and better leptin sensitivity. “When your insulin goes down, you don’t crave carbs.”

Leptin helps to regulate your appetite and energy expenditure. When you’re leptin resistant, you won’t get a sugar high, your body will try to conserve energy and find more food.

Lustig says that “if we could fix leptin resistance, there wouldn’t be obesity.” And that the very act of losing weight makes you more leptin sensitive and so you have more energy and less food cravings.

“Insulin blocks leptin,” so that your body thinks it’s in a state of starvation even when it technically isn’t.

Lowering insulin actually makes the body leptin sensitive.

(So, it isn’t really fair to ask kids or anyone to go exercise because they are lacking in energy due to their weight issues or bad diet choices. So, you’ve got to start with their diet or, as Lustig might suggest, hormone replacement therapy.)

He goes on to say that “our body is like two compartments. Our heart, our brain, our lean body mass, and our fat. And so there is a competition going on for the same molecule of glucose. What determines which way the glucose goes? Your insulin. The less insulin, the more goes to you. The more insulin, the more goes to fat.”

Fructose is a bad sugar that contributes to the obesity epidemic – to insulin and leptin resistance.

“If you take in 120 calories of glucose, the majority of the glucose gets metabolized by the rest of the body… Only 24 calories hit the liver… The overwhelming majority of glucose gets converted to glycogen. Glycogen is non-toxic. Glycogen is liver starch. Your body wants to make glycogen.”

“Glucose is not very good at contributing to obesity because not much of it gets stored as fat.” (He goes over the biochemical process behind this in the video) “You would have to eat a whole lot of glucose to get fat.”

“Consume a 120 calories in sucrose. Glass of orange juice. The glucose will do the same 20 80 split… but the entire bolus of fructose will have to be metabolized by the liver… If you overwhelm your liver to deal with carbohydrate, what happens?”

(For a description of the various types of sugars check here.)

“Fructose induces insulin resistance which then induces leptin resistance.”

(Seems to me, then, that the best carbohydrate to eat is starch, which is a polymer of glucose molecules.  So let’s not encourage our kids to eat as much fruit as they want but rather to eat starchy foods for their carbs. Weston Price actually noted that the many traditional kids refused fruit even though it grew all around them and preferred, instead, starch.)

The Darwin bit is mentioned at the end, which I won’t spoil for you. Essentially, it boils down to seasonal insulin resistance.

Enjoy the video. It’s long and complex but with all the talk of carbohydrates in the Paleo community right now I thought it might be helpful. Plus, I really am going to post an article soon about low carb, what I think about it these days, why you might not want to do it, and how you can succeed without it.

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  1. I’m still relatively new to Paleo and finding my feet. The more I read, watch and practises this lifestyle the more it makes complete sence.

    Thanks for the post…

    • Awesome! And then a little later, the more you read the more none of it will make any sense anymore!

      • That is just how I feel Peggy!!:D
        I don’t know anymore what to eat, vegies, fruits, starch, rice.. I’m all mixed up!

  2. The point about leptin interests me … I remember when I first learned about leptin, I was probably in my late teens and was just starting to put on weight. I remember thinking that I must not have had enough leptin, because I was constantly hungry even though I was gaining weight. Now I believe this had to do with the fact that I was an undiagnosed Celiac and thought that eating healthy meant unbuttered toast.

    Dr. Lustig is a smart dude. (I’m at work right now, so I’ll have to watch the video later, but I’ve seen “Sugar: The Bitter Truth” which was excellent.)

    • Where do we find starch except in sweet patato? In fruits also, or are all fruits fructose?

      • There isn’t starch in fruit. It’s just sugar. Starch is found in potatoes and all grains, but also in other roots like taro and yuca (tapioca). I think the reason why Paleo people are suggesting rice these days is because it skips the liver and the starch itself is an amylose which is slower to digest, hence easier on your blood sugar levels.

        Here’s a post about various types of tubers

        I don’t think that eating a little bit of sweet potato (which contains fructose) would be bad for most people. Maybe not so great for leptin resistant individuals…

      • Squash or yams are good starches if you handle them ok.

  3. One or two servings of fruit a day (as Paul Jaminet recommends) seem to be safe for that is just about what the liver can handle. Nothing compared to the fructose contents in sweets/juices/soft drinks! I occasionally use rice syrup as a sweetener for it is 100% pure gluccose (at least the organic brand I use) but I remember that you are allergic to rice so you wouldn´t wish to experiment with it! However, it is great in my homemade ice-cream! An interesting observation for me is that when I first went Paleo/Primal I experienced problems to maintain my happy weight (started to gain weight). When I started to follow the Perfect Health Diet style of Primall and made sure that I ate aroung 400 kcal of carbs, mostly from starch, I experienced weight loss and have no problems staying at this weight I feel best. I wasn`t aware that vegetable carbs do not count…But this is different for everyone as every metabolism has its own mechanism…I have been tested positive for fructose malabsorbation so overdoing it won´´ t happen in my case (sometimes intolerances protect against bad choices :-))

    • Intollerance has certainly protected me from a lot of bad choices! It’s kind of awesome actually.

      I’ll read that link in a bit. It looks like a great read! Thanks for passing that on.

  4. Peggy (or anyone),

    Okay, very unrelated but since you’ve touching on nutrition matters and its been on my mind for few days now…; Anybody have any recommendations/thoughts on post-workout nutrition?

    I’ve been hearing the following suggestions:
    1) high carb high protein
    2) high fat high protein
    3) fast

    Related to article, I’m probably more in favor of the archevore/stephen realm, whereby carbs are not frowned upon at all.

    I’ve been upping my carbs rather considerably since going 5x/week crossfit, up from 2x/week (I’d guess ~ 100-200g /day normally from sweet potatoes & 1 fruit if any). Considerable increase in performance/longevity in a CF setting.

    Also, I will say I went low-carb (only veggies) for a 3-4 week period to drop about 10lbs prior to all this. But I started to feel extremely drained and apparently really cranky (according to others…).

    Tying it all back, I’d have to agree if one’s goal is to lose weight, my exp has been going low-carb paleo, with emphasis on food quality, is hands down the best method.

    • thanks Peggy!

    • Well, personally, post workout I don’t eat anything, usually. As I understand it, we produce growth hormone while we exercise and the process stops if we eat. If we don’t eat, however, we keep producing it for a while. But before your workout and sometime after, eating as normal seems ideal to me – carbs, protein, and fat. What do you think primal man did, isolate macro nutrients after a “workout”? I like to think of it that way.

  5. I have just found that article on Paleolithic diets not being very low carb:
    The idea about the reason for “carb intolerance” are interesting…They also promote to add some (more) starch to the diet…

  6. I watched the whole video, it is really thorough. Most of the things I knew already( about Hfcs, coca cola, fast food etc), but the thing that is really frightening and new to me is that the fruits are bad for you since they contain fructose.
    And according to dr.Lusting, glucose is good, and so are the grains. And that is opposite to Paleo.

    In summary,veggies, sweet patato and squash are good, and fruits aren’t. Did I get it right?

    • Right, fruits are bad, at least too much of them. Maybe it would be optimal for a person to avoid them, maybe just important for people who ate SAD all their lives and are trying to rebuild their health. It would seem that it isn’t a good idea for “low carbers” to rely on just fruit for their 50-100 grams of carbs.

      So yeah, glucose better than fructose, starch better than glucose.

      BUT he didn’t say anything about where to get that starch (in this video) and how much one should eat. So that’s not exactly unpaleo.

  7. You should definitely check the Perfect Health Diet website for further information on starch/glucose. Paul really writes for the scientifically minded and the stuff there is well researched. I also learned there that children need considerably more glucose than adults do because of their growing brains…But I do not think that moderate fruit intake is harmful. Our organisms have pathways designed to handle fructose which might mean that we are programmed for a certain (but limited) intake (as in moderate fruit intake)? Just an idea…

    • I have been reading Paul Jaminet’s articles now for a couple of months. I quit eating low carb this summer which I came to through self-experimentation but then I started reading Paul Jaminet to gain some intellectual comfort with the idea.

      Since low carb was proved so healing for my brain and my skin, it was really hard to give it up, but I have found a way to add carbs in so that my skin and mood don’t suffer. I think it depends on the person for fruit intake. Maybe those with slugglish liver could stand to go without it. Personally, I get really hypoglycemic when I eat fruit. Moderate doesn’t work for me at all.

  8. Oh yes, I’ve definitely reached that stage. Having to go through trial and error with every little thing to see what I can and can’t tolerate rather than just believing what I read.

    • Reading helps us build our own foundation for sure, but it just isn’t the be all end all. Ultimately we’re going to have to tweak somebody elses suggestions no matter what.

  9. Peggy, what is your way to add carbs without damage to skin and mood?
    Please share:D

    • I am actually writing an article about it right now because it’s so huge for me! But basically it’s sugar. I don’t eat fruit, I don’t eat fiber, and I do eat sugar, preferably glucose. I should have this article posted by wed or thurs where I’ll go into more detail. You know I can’t eat fruit or fiber so carbs have just been so off limits for me. This summer I stumbled upon sugar, found it works perfectly with my digestion and doesn’t cause acne. I have gradually been increasing the amount and have only been doing better overall, not worse.

  10. wow, I can’t wait for the article!

    I still need more time and practice to figure out what makes me ill, but I have a feeling that fruits are not on my side. I haven’t been eating them for couple of days now and I am feeling better.I hope it’s the fruits rather than sth else that I forgot having eaten;) But when it comes to veggies, I am still clueless!
    One thing I now for sure is that I can handle meat, fish and fat very well:D and on that diet my skin is clearing up for the first time in my adult life.

    p.s I renderred tallow today for the first time in my life, I’m so proud:DD

    • That is so exciting! I remember the first time I got clear skin. I can’t even begin to explain how amazing that was. I had always been so embarrassed and felt so hopeless. Reclaiming your health, though, does take time, so don’t be discouraged by ups and downs. It sounds like you’re on to something though!

  11. And broth is cooking on the stove;)

  12. I am curious what kind of sugar (other than rice syrup) you use that is pure glucose? Everything else I have found so far is sucrose which is 50% glucose, 50% fructose) but I would like to experiment with sources of glucose other than rice syrup, mainly because it is so expensive!

    • I’m majorly allergic to rice so no rice syrup for me, but dextrose or corn sugar is glucose as is corn syrup (not to be confused with high fructose corn syrup, which undergoes enzymatic processing).

      • Looking forward to the Low Carb post. My question is do you differentiate between cane sugar vs. beet sugar? Is one better then the other etc.?

        • Cane sugar and beet sugar are both sucrose and so they are half glucose and half fructose. A little fructose is probably fine but, as Lustig was saying, it goes through the liver for metabolism which is not optimal.

  13. Wow, fascinating points! I recently read about the issue of fructose in The Perfect Health diet, and have been avoiding it ever since. I definitely feel the difference!

    I really appreciate you taking the time to hit the highlights from this video. Great stuff.

  14. Fructose is only bad if you avoid the Sun and you’re deficient in Vitamin D.

    Fructose stimulates production of pre-Vitamin D.. so avoiding fruit and getting Sun will not yield much Vitamin D.

    If you wanna hijack the body, go high meat paleo and avoid the sun.

    I’m sick of hearing how much bad rep a piece of fruit gets. Its mother nature. Not man-made.

  15. You’d love it at our place. Just slaughtered four lambs last week, and they’re ready now, so our freezer is full with lamb, leg roasts and chops. Now we’re waiting on our orchard trees to be ripe – should be ready in about a week from now, then I’d be jamming and making sauces.

    You have never tasted lamb until you’ve tasted home grown organic lamb barbecued in homemade plum sauce, made with manuka honey from our own hives. We grow all our own salad veggies too. It’s barbecue season down here now (in New Zealand), and life is looking good.

    I don’t know anything about this primal thing you’re talking about, but it sounds like you’d fit right in here!

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