What causes obesity: sugar, carbs, or food palatability?

Human body is an amazingly complex system of biological processes and our understanding of its inner workings is still evolving. Right now there is a very interesting debate going on in the Paleo community between Gary Taubes, author of the Good Calories, Bad Calories and Stephan Guyenet on the causes of obesity; carb-insulin hypothesis going against food palatability hypothesis.

Due to this high profile debate and some other information I have found recently, I decided it would be only fair to present some opposing views and counterpoints to some of the things presented in the 7-Day Crash Course in Nutrition and Health -article. However, I want to emphasize couple things: What causes obesity and what is an effective way to lose weight are two separate things. E.g. an infection is treated with antibiotics, but it is not the absence of antibiotics that caused the infection.

The other thing I want you to keep in mind is that the information in my Crash Course article is still extremely useful and important. By implementing just a fraction of it – for example eliminating processed foods, wheat, and getting enough sleep – can dramatically improve your health and well-being.


Counterpoints for the carbohydrate hypothesis of obesity

This article by Stephan Guyenet gives a good overview about arguments that do not support the carb-insulin hypothesis of obesity. Similar evidence is clear from Staffan Lindebergs studies of the Kitavans where the population consumes about 70% of calories in carbohydrates but are remarkably lean and healthy. There seems to be something else than just the amount of carbohydrates consumed that makes people overweight and obese.

However, this does not mean that a low-carbohydrate diet would not be a powerful tool for weight loss, but it implies that something else than simply restricting carbohydrate intake might be behind what makes low-carbohydrate diets effective; a low-carbohydrate diet naturally also minimizes grain and sugar intake. People also tend to feel more satiated when following a low-carbohydrate high-fat diet and consequently reduce their caloric intake without even noticing it.

The food palatability hypothesis advocated by Stephan is not without its own problems and logical fallacies. Todd Becker has written a great article on this. It is also interesting to read because it proposes a scenario in which both the food palatability and carb-insulin hypotheses can coexist and be simply parts of a larger puzzle.

Soon after the critique Stephan also posted an article about his current thinking of what are the different causes of obesity. It is well worth reading.


Is Lustig a sugar Nazi?

Ok maybe this goes a bit too far, but based on some news articles where Dr. Robert Lustig has been interviewed he seems to be headstrong about getting sugar banned. Similar to all the fuss about cholesterol and saturated fat years ago. However, apparently Lustig was not entirely accurate with biochemistry in his Sugar: The Bitter Truth lecture.

Dr. Richard Feinman has put together a nice article about where Lustig went wrong. Interestingly this seems to not only take some blame away from sugar, but also coincides with the message of Wheat Belly that the main culprit behind obesity epidemic is wheat:

“[Wheat] is the darling of the food industry because it is their nicotine. It is the stuff that makes you come back. It is the stuff that makes you hungry in a 90- to 120-minute cycle, and so if you eat more, you consume more, you buy more, they make more money. So this is the reason, I believe, why, if you look at the products on the supermarket shelf, it’s tough, it’s really tough, to find foods that don’t contain wheat because it stimulates appetite.”

The Paleo Solution – Episode 95


I would love to hear what you think of all this. Also, I strongly recommend downloading and listening to the Paleo Solution Episode 95.

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  1. says

    The sugar v. starch idea doesn’t make sense to me because starch breaks down into sugar during digestion. I don’t know whether fructose or something else is to blame, but anecdotally, there are people who gain weight and suffer from poor blood sugar control when they cut out sugar but still eat starch.

    Whether an approach like substituting whole, real foods like fruits and tubers v. cutting carbs helps you depends on your problem. If it’s lack of nutrients, eating a banana instead of a Twinkie will help. If it’s wonky blood sugar, you might as well enjoy the Twinkie if you don’t like bananas. (I’m exaggerating a bit to make a point.) Olives or an avocado will beat both of them in that case. I think low-carb diets help with both problems: the typical carbs people eat are empty calories with antinutrient properties (e.g., phytic acid in grains, sugars and grains stripped of nutrients). Substitute a scrambled egg for a bagel or cereal and you’re getting more nutrients (and less carb). Substitute a hamburger with no bun for a plate of spaghetti, and a small salad and full fat dressing for a box of crackers or cookies, same thing.

    I don’t hear much about this, but Taubes makes the point in Why We Get Fat that obesity is a disease of malnutrition. Low carb diets address this problem.

    • Sami says

      Hello Lori and thank you for your comment. I try to reply to specific points here:

      “…there are people who gain weight and suffer from poor blood sugar control when they cut out sugar but still eat starch.”
      – Is it starchy or higher carbohydrate diet that causes weight gain in the first place? Granted, low-carb approach will help stabilize blood sugars and likely results in weight loss, but we have populations like the Kitavans that refute the hypothesis that high carbohydrate intake causes weight gain. I might add, that not all overweight people are insulin resistant. This does not mean that insulin resistance wouldn’t be an important piece of the puzzle, but it seems to not be the only determining factor.

      “Whether an approach like substituting whole, real foods like fruits and tubers v. cutting carbs helps you depends on your problem. If it’s lack of nutrients, eating a banana instead of a Twinkie will help. If it’s wonky blood sugar, you might as well enjoy the Twinkie if you don’t like bananas.”
      – I agree with you when it comes to stabilizing blood sugars but I can’t help feeling that focusing too much on it is akin to focusing on a symptom, not a cause. I assume we agree that those wonky blood sugars are a result of insulin resistance, right? But what causes insulin resistance? It has been shown that low-carb diets help restore insulin sensitivity but is it the low amount of carbohydrates that does it, or is it something else? E.g. something to do with avoiding processed foods, grains, vegetable oils, and fructose? Or simply the effect of lower caloric intake that seems to come naturally to those following a low-carb diet?

      “Olives or an avocado will beat both of them in that case.”
      – Fo sho :)

      I have to say that I’m a little worried about low-carb diets because at least in Finland they are gaining a lot of mainstream attention and more “low-carb” products are hitting the shelves. If the benefits of low-carb diets have been more related to food quality and eliminating grains, the results of people eating processed low-carb foods may very well turn out to be harmful instead of beneficial.


  2. says

    Hi Sami, thanks for your thoughtful reply.

    I didn’t mean that a high carb diet necessarily causes weight gain, just that I don’t share Dr. Lustig’s view that sugary diets and starchy diets are two very different things. People do lose weight on high-carb, low-fat diets (I once did, without restricting calories).

    I don’t think you necessarily need to be insulin resistant to be hungry due to blood sugar. You’ve heard the chestnut about being hungry an hour after you eat Chinese food, right? Even normal, healthy people get falling blood sugar, and it can make them hungry. Graph of normal blood sugar reaction here: http://www.phlaunt.com/diabetes/16422495.php. For a lot of people, weight gain could be as simple as eating high-carb meals, getting hungry and snacking. If you’re interested, here’s a page about blood sugar control written by Jenny Ruhl, an amateur researcher who studies diabetes. http://www.phlaunt.com/diabetes/14046621.php. SSRIs and corticosteroids are two other things that can increase risk for diabetes.

    I totally agree with your quote about wheat. When I quit eating it last year, my appetite ratcheted way down, and just eliminating that one food, I started losing weight. It’s an appetite stimulant. In fact, I could (and would) eat a whole box of cookies or four bowls of cereal or a bunch of brownies at one go, a problem I never had with any other food. The wheat-exorphin food reward could play a big part in obesity.

    Pre-packaged low-carb foods haven’t hit the shelves here. (In fact, the low-carb chocolate ice cream disappeared.) Among low-carbers here, the trend is more towards paleo or at least minimally processed foods. Wheat won’t ever go away, but I think in my lifetime, most people will drop the pretense that it’s a health food.

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