I mentioned in my previous post a new study on diet diversity, which caught my eye. Moderation is a pretty common theme among many dietitians and public health folks. Likewise, you might also hear that a diverse diet is healthiest, one that includes a wide range of fruits and vegetables, whole grains, lean protein, etc, etc.
But more research suggests otherwise.
I’m not going to go into all of the research showing considerable metabolic health benefits of nutritional ketosis, which is by no means an example of moderation. In these cases, fat makes up around 80% of calories. So, one could easily argue this isn’t very diverse, but it’s hard to refute that there are significant health and longevity benefits.
Back to this new study though.
A team of well-known nutrition researchers looked at diet diversity and its impact on central obesity (as measured by waist circumference) and incident type 2 diabetes. They used a sample of almost 7,000 ethnically diverse adults (38% Whites, 28% Blacks, 22% Hispanics and 12% Chinese Americans) from the Multi-Ethnic Study of Atherosclerosis (MESA) cohort aged 45-84 from six U.S. study centers (Columbia University, Johns Hopkins University, Northwestern University, University of California, Los Angeles, University of Minnesota, Wake Forest University).
Using a standard questionnaire, researchers asked each participant to indicate how frequently they consumed a particular category of food each day and the portion size (small, medium, or large). Responses were then used to estimate three aspects of dietary diversity: 1) count, 2) evenness of the food intake distribution and 3) the dissimilarity of food items consumed. The researchers also used several different validated indices to assess dietary quality.
Now to the interesting part: the results.
Participants with the highest amount of “evenness of energy distribution” (i.e. less diversity) were younger, more physically active, more likely to have higher education and were more physically active compared to those with the lowest.
Similarly, participants with greater dissimilarity in their diets (i.e. more diversity) were also more likely to be younger, more likely to be males, to be Whites, and to have higher education.
Now here’s the kicker. The same participants (those with greater diversity in their diet) also had higher BMI, and were more likely to be smokers compared to those in the lowest amount of food diversity.
Now, when it came to consumption of healthy foods, less diversity came out on top again. Researchers found that, “consumption of healthy dietary factors (e.g. fruits, vegetables, nuts) showed inverse correlations with food dissimilarity, while consumption of less healthy factors (e.g. soda, trans-fat, desserts) was positively correlated with the same diversity metric.”
This means that those with a less diverse diet were more likely to have a healthier diet. The graph below illustrates this.
On to the relationship between diet diversity and type 2 diabetes.
After about 10-years of follow-up, the researchers found no association between food count, evenness or dissimilarity and risk of type 2 diabetes. In other words, a more diverse diet didn’t have any protective effect against type 2 diabetes.
Likewise, researchers didn’t find any association between diet diversity (using 2 of the 3 metrics) and waist circumference. Interestingly, though, using one of the diet diversity metrics, researchers actually found a more diverse diet to be associated with a higher gain in waist circumference after 5 years.
So, what’s the take away?
Your diet doesn’t necessarily have to be extremely diverse to be healthy. I eat the same thing for breakfast and lunch every single day. I’ve found a combination of foods that I enjoy, are easy to prepare, and pack a nutritious punch. When I deviate from this, I know it. I’ll feel different and my weight may even fluctuate during that week (but more likely the next).
What I’ve done, and what the research supports, is that it’s possible and even healthier, to create a habit for your eating. And as long as you’re covering your nutritional bases (i.e. macro- and micronutrients), it’s okay, and even advantageous, to eat many of the same foods. For me, I don’t have to think about what to buy at the grocery store, what to make for lunch in the morning, or worry how long it will take. I’ve already calculated it out, so now my brain more or less runs on autopilot. My wife and I even have the exact same sequence when grocery shopping. We do it the same way every time, in the same steps.
Our diets don’t need to be complicated or diverse. Find the right mix of foods and stick with them. Then, with the right planning on the front-end, you can build habits and routines that help keep your food choices on the right track. And once specific, healthy food choices become habit, you can use your brain power for something far more interesting.