Think of something you are sure is true. There are obvious, accepted facts, like the earth’s orbit of the sun, and there are more complicated matters that have an emotional connection to self conception - belief systems, codes of ethics, or views on a particular social issue. Under what conditions would you reevaluate one of these? Can you imagine something - new evidence or an experience - that would change your mind?
The example of the Copernican conception of the sun is an interesting starting place. There is little we directly experience to suggest that we’re all on a huge rock sphere circling a far larger ball of fusion hurtling through an endless void. But once the nature of our solar system is understood, it has tremendous explanatory power and elegance, and this understanding has allowed the development of everything from accurate navigation systems to satellite internet to insights into the origins of the universe. Its fundamental correctness is so well established that I cannot envision any scenario that would cause me to question it. (The fact that a significant and increasing number of people apparently don’t share this view is horrifying.)
But how to assess science gets more complicated when dealing with dynamic systems, particularly when those dynamic systems are human bodies and what they should eat. There are few things that at once elicit stronger opinions bolstered by so little certainty as what we should be stuffing ourselves with. Keep an eye on the health section of a newspaper and you will see an endless string of studies, breathlessly reported, that give conflicting messages on the healthfulness of cholesterol, fat, carbs, fish oil, resveratrol, vitamin C, and basically every other nutrient that’s been studied in any depth.
For the first quarter century of my life I more or less believed the consensus that fat and cholesterol are singularly unhealthy. I was vegetarian or nearly so for twelve years. Then my brother Ed gave me the book Good Calories, Bad Calories, which convinced me that excessive consumption of carbs lay at the root of type 2 diabetes, heart disease, and other diseases of civilization. In the decade since no single work has completely shifted me from this view, but a steady drip of contradictory information has eroded the confidence I once felt about it.
As someone who finds purely mechanistic explanations for people and what they do a bit depressing, I actually enjoy this state of uncertainty, which studies like the one making the rounds for the past week emphasize. It sought to assess the difference between low fat and low carb diets when implemented in real life. There was no calorie counting, just counseling about dietary choices, and the findings were fascinating:
-On average, participants in both cohorts lost significant weight.
-Many participants reported feeling that the dietary counseling shifted their relationship to food in a fundamental and healthy way.
-The study examined several biological markers, none of which correlated with the effectiveness of one diet over another.
-More surprisingly, individual with poor insulin sensitivity did as well on the low fat as on the low carb diet.
So what did the diets have in common? In both cases participants were encouraged to eat unprocessed foods - vegetables, meats, and dairy in the low carb group, vegetables, lean meats, and whole grains in the low fat group. They were all instructed to consume whole, unrefined, nutrient dense foods, and to prepare them at home if at all possible. This seems like a sensible way to eat!
As is always the case when it comes to diet, this study is far from definitive. The low fat group wasn’t super low fat. Neither was the low carb group super low carb. It is possible that more extreme changes would have led to different results. But there is also utility in finding out what people can actually implement in their lives for a full year with only encouragement and instruction.
A final note - it’s worth pointing out that both groups were encouraged to give up refined sugars. For all the murkiness about macro and micronutrients, the one aspect of dietary science I am most confident in is that cutting back on sweets is probably not a bad idea.