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An article in the New York Times announced that a new study shows “The Key to Weight Loss Is Diet Quality, Not Quantity,” which caught my eye because scientifically speaking, the quantity of your diet is absolutely the primary driver behind your weight. It’s an indisputable scientific fact that if you burn 1500 calories a day but you eat 2000 calories worth of bananas every day, you will gain weight. If you eat 1000 calories of Twinkies every day, you will lose weight. It’s ultimately about quantity, not “quality.”
Reading the article, as usual, debunks the headline. In case other people are confused, I wanted to make a video laying out exactly what is right and what is wrong about the headline, the article, and the study behind it.
The study itself did not test “quantity” versus “quality” in diets, and so it should absolutely not be used to support one over the other. If it were comparing those two factors, you could imagine it would involve two groups of people (at least): one that ate “high-quality” food (nutritious, home-cooked, or whatever other trait you consider high-quality) in whatever amount they wished, and one that ate whatever food they wished in low-quantity (fewer calories than they burn on a daily basis). In fact, this study compared two groups of people, all of whom ate “high-quality” food and none of whom counted calories in their food. On average, both groups lost some weight, but we have no way of knowing if they lost more or less weight compared to people who learned to count calories.
The actual difference between the two groups was that one group ate low-fat foods and the other ate low-carb foods. The actual purpose of the study was to determine if people’s genetics or insulin levels impacted how much weight they lost on these diets, as people like Gary Taubes have made millions telling the world. The study results contradicted Taubes’s assertions: neither insulin levels nor genotype predicted how much weight subjects lost. In other words, sorry, but a calorie is a calorie.
That should have been the headline but instead they went with this idea that can almost be interpreted to contradict those findings: calories don’t matter and it’s all about what foods you choose to eat, despite the fact that the study found that the actual foods you eat don’t matter. In a perfect world, that wouldn’t be the takeaway here, though it could be the impetus for another study to follow-up on this one. When you conduct a study and you find something strange that you weren’t looking for, you don’t generally publicize that as your finding — you set up a new study, with a new hypothesis, to further investigate that strange thing and verify that it’s not a statistical blip.
Until we get another study, I will say that it IS interesting that people, on average, lost weight on this diet in which they weren’t actively counting calories. The diet involved teaching subjects how to choose more nutritious foods while avoiding heavily processed food that contains a lot of sugar, and how to pick whole wheat over white bread or brown rice over white rice.
Does the fact that they lost weight mean that calories don’t matter? No, just the opposite — in fact, the study found that the subjects ended up consuming fewer calories than they previously had, which is why they lost weight. So really, this is not a problem of physics as much as it is one of psychology — the study may suggest that people can be tricked into consuming fewer calories by teaching them to eat more nutritious foods. And this makes sense, considering that it’s really, really difficult to eat 2,000 calories of spinach and it’s really, really easy to eat 2,000 calories of ice cream. When you avoid “junk” food, you’re more likely to eat fewer calories by accident.
Here’s why that’s an important distinction, compare to the headline: we have no idea how sustainable that is. If people don’t understand why they’re losing weight, they risk gaining it back if they find a “whole” food they love that is a calorie bomb (like avocados, for instance) and overeating again. Or, they may get fed up with never having “treats” and give up their new lifestyle entirely. One of the nice things about calorie counting is that I know I can have an ice cream sundae if I eat fewer calories for dinner and add a run into my day. One of the reasons many people give up on “diets” is because they miss eating the things that used to bring them joy.
So to sum up, it’s an interesting study that disproved its hypothesis, which had nothing to do with calorie counting. And it’s a misleading headline in the New York Times that is only partially redeemed in the article. But hey, I bet Gary Taubes is relieved that they made the story about calorie counting instead of the actual result of the study, which debunked his life’s work.