Tuesday, November 24, 2015


YMMV. Or “Your Mileage May Vary.” That’s what many of us type 2 diabetes patients have discovered when it comes to diet. What works for one person may not work so well for another.

For example, some patients report that they can eat rice without a great effect on their blood glucose (BG), but potatoes make their BG levels soar. Others report the exact opposite.

One problem with such annecdotal reports is that we often don’t know how the various foods were cooked, how much the people ate, or what they ate with the foods they’re reporting on. For this reason, medical professionals tend to ignore such annecdotal results and instead rely on huge nutritional studies that usually report results only as averages, neglecting the “outliers,” or those whose results were far from the mean.

That means that if you’re an outlier yourself, the “evidence-based medicine” results from the nutritional studies, or the diet advice of some diet guru, may not apply to you, and if you try to follow this advice and don’t get good results, people may accuse you of being “noncompliant” or not doing what they told you to do.

But now it appears that even the professionals are beginning to accept that we’re all individuals with individual responses to various foods. And we now have a well-controlled study to support this view.

The study by researchers at the Weizmann Institute of Science in Israel used continuous glucose monitors to measure the BG levels of 800 healthy and prediabetic people after their meals for a week, and put this information along with what they ate, information from stool samples, and other physiological information into computers and analyzed it. They even gave them identical foods for some of their meals.

What they found was that the people differed greatly in how they responded to various foods; the glycemic index, a measure of how much your BG levels are supposed to rise after eating carbohydrate, varied among the participants. “In some cases, individuals have opposite response to one another, and this is really a big hole in the literature," said Eran Segal, the lead author of the study.

"After seeing this data, I think about the possibility that maybe we're really conceptually wrong in our thinking about the obesity and diabetes epidemic," he added. "The intuition of people is that we know how to treat these conditions, and it's just that people are not listening and are eating out of control--but maybe people are actually compliant but in many cases we were giving them wrong advice."

As an example, they cited the case of an obese woman who couldn’t lose weight despite trying hard. It turned out her BG levels spiked when she ate tomatoes, and because they’re supposed to be a healthy food (“eat more fruits and vegetables”), she was eating a lot of them  and her BG levels were spiking every day.

Not only glycemic index but other parameters resulted in different effects in different people. Some people saw increases in BG levels after meals that were unrelated to the carbohydrate content. In most people, fat reduced postprandial BG levels, but in some it had no effect.

What was especially interesting was that the variation in responses to food seemed to be linked with the microbiota, the bacteria in their guts. Although the microbiota tends to be stable throughout one’s lifetime, the researchers said they were able to alter the patients’ microbiota by controlling increases in the BG levels.

I think this study is important in the context of “diet wars.” Low carbers and low fatters and other diet gurus often act as if theirs is the only diet that will work and everyone should follow in their footsteps. Their diets do work extremely well for some people, but they don’t work for everybody.

If the Kitavans thrive on a high-carb diet, that’s the diet they should follow. If the Inuit thrive on a high-fat diet, that’s the diet they should follow. The diet you should follow may depend on the bacteria in your gut, and that may depend on your genetic heritage, although it can be somewhat altered in various ways (diet, antibiotics, etc.).

In the diabetes community, I think most people are aware of the concept of YMMV, and we’ve adopted a philosophy that takes it into consideration, namely “Eat to Your Meter.” If some food like tomatoes makes your BG levels soar, don’t eat that food. If it’s relatively benign for you, go ahead and eat it in moderation, and don’t worry if someone else says it’s no good for them.

For those without diabetes who simply want to lose weight, an analogous approach would be “Eat to Your Scales.” If you tend to gain weight when you eat certain foods, then don’t eat them.

Although most of us would agree that a diet of nothing but cheeseburgers and fries is not healthy for anyone, what is healthy is less certain. Remember YMMV and eat what works for you.


  1. Thank you for sharing this. I am in the process of skipping doctors because mine didn't believe me when I shared information about my diet. Cookie cutter diets (one size fits all) do not work for me.

  2. Pondering Cat, I understand your frustration. Is there any chance you could find a doctor who would be more open-minded?

  3. Two of the authors of this paper answered questions here: https://www.reddit.com/r/science/comments/3txns6/science_ama_series_we_are_david_zeevi_and_tal/

  4. Good post but, in some way, we knew this from the huge error bars in those big studies. But I don't think anybody believes anything in nutrition anymore.

    1. True about the error bars, but not every reader sees or understands error bars. Some days I don't think I believe anything anymore. Not even Santa.

  5. Gerald Reaven among other researchers used to plot individual subject responses rather than amalgamate them using sophisticated statistics. It's really interesting to see most people showing a similar response, but with significant differences in magnitude, and a few whose graphs zing off in a completely different direction.

  6. Yes. I've found more people doing that, and it's interesting. I wish they all did it.