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For decades, we have pursued a low-fat diet as a public health message. So,
suddenly there seemed to be a turnaround. People were saying the low-fat thing was wrong. It was the opposite, it should be low-carb. It seems like there was a very active debate and
opponents on both sides. The acronym for our study is the DIET FIT study. We don't really believe that there is one diet for everyone. One of the things that would help people is if we could figure out which diet is best for whom. In this particular study, we wanted them to be both low-carb and high-quality, low-fat. We wanted there to be big differences. We weren't really sure how far we should push people. We had the idea that we would push both groups in the first eight weeks of the 12-month study to try to get them to 20 grams of fat or 20 grams of carbs. If you don't know much about diet, those are big changes from what they had at the beginning of the study. Another thing that we always hit home was quality. You want to go to the
Farmers' markets want you to cook more for yourself, they want you to sit down with your family. They don't want you to snack in front of the TV, they don't want you to eat in the car. We told both groups, low fat and low carb, with little to no added sugar if possible, with little to no refined grains if possible, and as many vegetables as possible.
With that as their backbone, they went in their low-fat or low-carb direction. That took some people. We ended up with 609 enrolled in the study with over 300 assigned to each diet.
They all had this wide range of potentially genetic predisposition, and potentially insulin/glucose regulation variability. The premise was, if we separated that out and looked at it by diet group, could we explain the individual variability that we consistently see in these studies? That's what we were looking for. In order to test the hypotheses that we made in this study, we had to meet a lot of the assumptions that we thought we were going to get. One of them was that people would lose a lot of weight in a weight loss study.
They did. They collectively lost 6,500 pounds. The other thing that needed to happen was that we needed people to have a wide range of weight fluctuations on both diets. Some of the participants lost 40, 50, 60 pounds, some gained 10 to 20, and everything in between. At the end of the day, none of our original hypotheses proved to be true.
There was a low-fat genotype. There was a low-carb genotype. High percentages of people fell into both categories, with no predictors of who was more or less successful on either diet. Regardless of what the insulin-glucose dynamics were, in our hands, there was no ability to predict whether one diet was better than the other. It closes the door on our two original hypotheses, but the future is full of opportunities to build on this study. People will want to know what to recommend.
I'm not going to recommend low-fat over low-carb, or vice versa, because that's not what we found. Depending on how you choose to define low-fat or low-carb in terms of choices and
dietary patterns, you can make a plausible mechanistic link between the field, low fat or low carbohydrate and better health.
The more I look into this, the more conferences I go to, I continually see three factors come up over and over again. Get rid of added sugar, get rid of refined grains, and eat as many vegetables as you can.
These are all huge challenges in the American diet and in many diets around the world. Yet we’re fighting over issues on the fringes of this whole debate, without getting to the heart of it. I think if we really focused on added sugar and reducing or eliminating refined grains, and worked with some of our favorite chefs to make vegetables even more appetizing and delicious, a lot of the debate would go away…
