Relevant to the Weight Loss Series I just published, a new study has found no significant difference in weight lost across 12 months in a low-carb vs. low-fat group. By itself, this adds to our understanding of weight loss, but it’s not revolutionary—we’ve known for awhile that it doesn’t matter whether your calories come from fat or carbohydrates when it comes to weight loss. More revolutionary is the study’s concurrent investigation into the effect of genotype on weight loss.
Participants in the study were analyzed for a number of genotypes that have been hypothesized to be relevant for weight loss. Specifically, the genotypes fell into either a “low-fat” category (meaning a person with this genotype should fare better on a low-fat diet) or a “low-carb” category; there was also a single “neutral” genotype. Hypothetically, the participants who had more genotypes in common with the diet they were prescribed should have lost more weight since their genetics ostensibly lined up, but this isn’t what happened. Instead, there was no apparent interaction; genotypes didn’t have any impact at all.
Is this surprising? I don’t think so. We’ve come a long way in our understand of genetics, but we’re nowhere near to comprehending how multiple genes work together to influence something discrete like weight. We might be able to point to certain genes and say “this one influences weight in this way”, but we can do the same thing for height and still can’t make more than a guess about how tall someone will be as an adult. Unlike height, however, the ways a person can influence their weight are numerous, and the influences upon a person’s weight even more so; there are complexities not only in our individual metabolisms, but in our psychologies and environments as well.
I don’t know if we’ll ever reach the point where we can really say X diet is better for this person and Y diet for another, but it is interesting to untangle the genetic puzzle and try to understand how the pieces all contribute to who we are. There’s real scientific value in that, and we don’t really know what we’ll find down the line; it could lead to breakthroughs we don’t anticipate. Right now, though, it’s mostly marketing nonsense, and you can bet it’ll feed at-home DNA test kit makers claiming to be able to tell you how you should eat based on your genetics; it’s like the Blood Type Diet 2.0.
If you are trying lose weight, don’t worry about whether your genes are better for low-carb or low-fat—just stick to the diet that helps you restrict your calories, be mindful about your eating, and makes you happy. This is still the best advice, and even if we do enter a brave new world of genetic precision within our diets, you can bet this advice will remain relevant.
