Decades of diet culture has taught us that weight loss is all a numbers game. But does being purely quantitative with things like calories or carbs actually get you to your goal weight? Recent research says no, and suggests that the best way to lose weight may be to focus on the food source of your calories rather than their macronutrient composition. In fact, macros really may oversimplify the complexities of weight loss. Here's why.
Wait, so calories don’t matter?
Well, let’s get this straight. First, calories come from three main sources: carbohydrates, fats, and protein. Together, these three are referred to as “macronutrients” or “macros.” Calories are the fuel that allows our bodies to do everything, so they absolutely do matter. But when it comes to weight loss, the influence of calories may not be as clear cut as we’ve come to think it is.
And that’s why this study is changing the game
Now, an overview of the study. Two groups of people volunteered to live in a research facility for two weeks. During this time, they had unlimited access to food. But here’s the catch: one group only had access to unprocessed, whole foods like oats, strawberries, and chicken breast, while the other was limited to ultra-processed foods like breakfast cereal, canned peaches, and chicken nuggets. [1] So, you might expect these two diets to be drastically different in macronutrients. Less fiber and more sugar in the ultra-processed one, for example? Not at all. In fact, the researchers in charge made sure to match both diets in available calories, macronutrients, fiber, sugar, and sodium. [1]Participants were allowed to eat as much as they’d like of their assigned diet, and researchers monitored their weight over the two weeks. Their findings? The group eating only unprocessed foods lost a pound in two weeks, while the group who ate only ultra-processed foods gained the same amount.* [1]
Remember, these diets were matched in macros. So if weight loss really were just a numbers game, we would expect to see the same results in both groups. Instead, what this shows was that the source of macros, the foods themselves, were more instrumental in weight change than their mere macronutrient composition.
*Sure these numbers might seem small, but keep in mind—this wasn’t a trial designed for weight loss. Nobody set out with the goal to lose weight over these two weeks, and yet, everybody who participated changed weight in one way or another.
These foods act differently in our bodies. But why?
That’s the perplexing part. The image below illustrates how two foods that originate from the same whole food (oats) but have very different processing can still be closely matched in macros. If you just looked at the numbers, they could pass as the same food. But on our plate, they look very different, and this study showed that they likely look very different to our bodies, too.
So where does this difference come from? Well, researchers aren’t exactly sure, but it essentially boils down to total intake. Because, although the diets were matched in calories by design, the participants in the study were allowed to eat as much as they wanted, and there was a categorical difference in caloric intake between the groups. Those who ate ultra-processed foods ate significantly more than those eating whole foods. [1] So, it’s possible that something about ultra-processed foods makes us hungrier more often. But remember: this isn’t due to a lack of fiber, protein, or fat (the nutrients we know help us feel full the fastest) because the diets were matched in these characteristics. It wasn’t about glycemic load, either. [2]
So is it the processing itself that makes the difference? It’s possible. But the researchers acknowledge that we still don’t fully understand why that would be the case. There are plenty of healthy foods that we also deem ultra-processed: things like olive oil, dark chocolate, or even nut butters. [3]
The design of this study made its evidence very compelling, but we obviously need more to explore the same topic to build up the body of evidence—and answer these questions.
What to know about weight loss and macros
While we don't have conclusive understanding yet about why exactly processed foods act differently in our bodies than whole ones, we can still apply what we've learned to our daily lives:1) If you’re trying to lose weight, stick to a diet rich in unprocessed, whole foods. A diet rich in unprocessed food appears to promote hunger unnecessarily, which can make for frustrating internal struggle.
2) If you’re eating an unprocessed diet, quit counting calories! You’ll make progress without playing the numbers game when you focus on eating whole, nutrient-dense foods.
3) Having a treat every now and then is perfectly fine—and probably good for our mental health. But getting a majority of our calories from ultra-processed foods will severely hinder our ability to lose weight, even if we mind our macros.
4) If you do choose to enjoy an ultra-processed treat, be conscious of your serving size. We’re more likely to overeat these foods.
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