Which Is Worse for You: Sugar or Fat?

Hat tip to Joseph Kimball for pointing me to this video.

I recommend Olivia Gordon's Complexly SciShow video above. In the first 8.5 minutes of this 13.5 minute video, Olivia Gordon demolishes the idea that dietary fat is a big problem by going through the history of nutritional thought on this issue. In the last 5 minutes, she goes too easy on sugar, saying basically "It's complicated." I think she and her team did this in order to seem balanced, but she shouldn't have. Let me try to cut through some of her attempts to go easy on sugar. 

Even If the Only Harm of Sugar Is Causing You To Gain Weight, That Is Pretty Bad. After admitting that there isn't much to be said in favor of sugar other than the direct pleasure it brings, Olivia says that while sugar is likely to make you gain weight, it is gaining weight that is most likely to cause diseases, not the direct effects of sugar. Of course, if sugar makes you fat and getting fat leads to disease, it doesn't matter that much whether sugar causes diseases directly—or indirectly through causing you to gain weight. 

How Much Sugar is Too Much? Olivia makes the statement: "While most of us are likely eating too much added sugar, no one really knows how much is too much." This is a question that sounds clearer than it is. Let's look at some logical possibilities:

  • If the harm of added sugar is approximately linear, then the harm is simply proportional to how much one eats. A little bit of added sugar would be a little too much and a lot of added sugar would be a great deal too much. It is possible there is a linear harm that has a small slope, but Olivia is not claiming that added sugar is a trivial matter, so she is not going there.

  • Added sugar could be beneficial up to a certain point, then begins to be harmful. I don't see Olivia claiming this. If she intended this, it is strange she didn't say something like "Some people think a little added sugar is beneficial for health."

  • Added sugar could have a harm that accelerates with the amount of added sugar consumed. This is most in the spirit of what Olivia might mean by "... no one really knows how much is too much." (The extreme version of this is that there is a level up to which added sugar is totally harmless, after which it becomes harmful. That extreme version seems unlikely.) If sugar does indeed have a harm that accelerates with the amount of added sugar consumed, one should be very worried given how high average consumption of added sugar is relative to historical levels of added sugar—say, average levels prior to 1960. For example, if the harm of added sugar depends on the square of the amount of added sugar, then the harm of 100 pounds a year compared to 80 pounds a year would be 100/80 squared, or 1.5625 times as bad.


The Big Reasons to Avoid Sugar. After talking about the rise in popularity of lowcarb diets, Olivia points out that they are only good for about 11 pounds (5 kilograms) of weight loss on average. There are two key things to say about that. First, it is important to remember how much easier it is to avoid gaining weight in the first place than it is to lose weight once you have gained it. Insulin resistance, which is not so easy to reverse, is an important part of the story for why weight gain is hard to reverse. In economics and physics, when things are hard to reverse it is sometimes called hysteresis. Given how much easier it is to avoid gaining weight than it is to lose weight, a crucial question is how much a lowcarb diet or simply avoiding all added sugar from childhood on would contribute to avoiding weight gain. 

Second, what is crucial about a lowcarb diet—or even better, a low insulin index diet (see Forget Calorie Counting; It's the Insulin Index, Stupid)—is not so much that it, by itself will lead to weight loss, but that it makes it relatively painless to go for substantial stretches of time without eating anything. Going without food for a period of time is called fasting; in the kind of fasting I am talking about, you are encouraged to drink a lot of water while fasting. Fasting is the powerful technique for weight loss, not what you eat. But if you eat a lot of sugar, fasting is going to seem excruciatingly difficult. If you go off sugar, bread, rice and potatoes, and give yourself a month or so to adjust to that before trying to fast, I predict that fasting will seem much easier to you than going without food ever seemed to you before. If you are interested in weight lost, and start fasting after this period of adjustment to being off sugar, bread, rice and potatoes, you can start slow, along the lines discussed in "Stop Counting Calories; It's the Clock that Counts." But I predict you will find fasting so easy and so effective for weight loss that you will soon want to do somewhat more extended fasts. 

Tested Benefits of Going Off Sugar. Overall, Olivia makes it sound as if going off sugar might only benefit you a little bit. But a study she cites approvingly says otherwise: the Stanford DIETFITS Randomized Clinical Trial I discuss in "Why a Low-Insulin-Index Diet Isn't Exactly a 'Lowcarb' Diet." Currently, almost all highly processed food has added sugar. So going off sugar other than whole fruit implies also going off almost all processed food. Thus, going off sugar puts you squarely in the territory of the two diets that the DIETFITS Randomized Clinical Trial tested. They called one of the diets "healthy lowcarb" and the other "healthy lowfat," but don't be fooled. Given the fact that going off sugar currently means going off highly processed food, these two diets—and the possible diets in between—cover reasonably well the possible ways to eat if one goes off sugar (except for whole fruit). So the fact that both of these diets did a lot of good for people provides good evidence for the benefits of going off sugar. If you want to think of it as the benefits of going off highly processed food, that is also reasonable given the evidence we have. And you can get moral support on that from my post "The Problem with Processed Food."

(Note: Olivia cites the DIETFITS Randomized Controlled Trial, without naming it, on the point that there isn't much evidence yet for being able to predict from lab tests which approach will work best for each person. Currently, it is reasonable for everyone to begin with the same approach, then modify it based on their own experience.)  

How to Go Off Sugar. I highly recommend a rigorous approach to going off sugar. If you go off sugar, after a month or so, your body will adjust so that everything you eat tastes sweeter to you. I have been off sugar for about a year and a half; whole fruit tastes very sweet to me now, and even nuts with nothing added to them taste reasonably sweet to me. (To put the level of rigor I am talking about in perspective, I eat commercial salad dressing that lists 1 gram of carbs; it probably has some sugar in it. I eat chocolate with 88% cocoa in it, that definitely has some sugar. See "Intense Dark Chocolate: A Review." And I occasionally have some Halo Top ice cream, which is not entirely sugar-free.)

If you aren't rigorous about going off sugar, and just try to reduce your sugar consumption, you won't get full recalibration of your sense of sweetness. And your craving for sugar won't go away very fast, if at all. Nevertheless, you should get some benefit. For those who, contrary to my advice, are trying to reduce sugar consumption instead of almost entirely cutting it out, it is good for you to also think about reducing the amount of processed food you eat. By contrast, if you almost entirely cut out sugar, and look on the packages of processed food to see the almost ubiquitous added sugar, reducing processed foods would be automatic. ("How Sugar Makes People Hangry" has a list of names for different forms of sugar.)

Go for New Treats! Giving up added sugar doesn't have to mean giving up treats. The DIETFITS study indicates that you can replace sugar/highly processed food with dietary fat and be fine. For me, the Manchego cheese I buy from Costco and the frozen cherries from Costco or other whole fruit with half and half are great treats, as are cashews and almonds (also from Costco) that we bake ourselves. (Other than maybe in my mutual funds, I have no commercial interest in Costco! It is just a good place to get certain types of relatively healthy food at bulk prices.) The baked cashews and almonds are a perfectly good treat on the go; for me they have totally replaced power bars as a portable food when I am not fasting.  

I'll bet many of you can come up with tastier healthy treats than I can. I'd love to hear about your creations in a comment to this post or on Twitter: @mileskimball. Here are the rules of the game if you want to try:

  • Make the treat from scratch from unprocessed food. Note that flour counts as a processed food.

  • As long as it is unprocessed, it is OK if something is high-fat.

  • Don't do too much processing yourself in making it from scratch. For example, grinding something up or overcooking it probably makes it less healthy.

  • Don't add sugar or honey or agave. If you really need a sweetener, oligosaccharides, erythritol and maybe stevia could be OK.

  • Extra points for something being easy to make.

  • Simplicity is fine. It just needs to taste delicious and be healthy, not impress a professional chef.


Don’t miss my other posts on diet and health.

I. The Basics

II. Sugar as a Slow Poison

III. Anti-Cancer Eating

IV. Eating Tips

V. Calories In/Calories Out

VI. Wonkish

VIII. Debates about Particular Foods and about Exercise

IX. Gary Taubes

X. Twitter Discussions

XI. On My Interest in Diet and Health

See the last section of "Five Books That Have Changed My Life" and the podcast "Miles Kimball Explains to Tracy Alloway and Joe Weisenthal Why Losing Weight Is Like Defeating Inflation." If you want to know how I got interested in diet and health and fighting obesity and a little more about my own experience with weight gain and weight loss, see “Diana Kimball: Listening Creates Possibilities and my post "A Barycentric Autobiography.