Nuts Don’t Have As Many Calories As You Think

Whole nuts have fewer calories than were previously thought. For a few years, research confirming that fact has been trickling in, but now the labels on foods are beginning to change. One KIND bar that was formerly 200 calories, for example, will now be labelled as containing 180 calories.

KIND told me via email that they believe they’re the first snack brand to adjust their labels. Most brands pull calorie data from a USDA database, which hasn’t been updated yet, but the science behind the calorie reductions is accepted.

How did we get the calories in nuts so wrong?

A calorie is a measure of energy. If you had a cool science teacher in high school, you may recall that you can burn a food—literally set it on fire—and measure the temperature of a beaker of water set above the fire. The hotter the water gets, the more fuel was in that Dorito or whatever you burned.

The human body is a bit different from a classroom fire, but we’ve known for over 100 years that our body can get about 9 usable calories out of each gram of fat in our food, 4 calories out of each gram of protein, and so on. Scientists have made adjustments to the calculations over the years to account for the fact that each food gets digested a bit differently.

But nobody looked too closely at whole nuts until recently.

They figured this out with a really gross experiment (sorry)

Nuts, being plant parts, are made of cells. Those cells have cell walls. The cell walls in nuts are particularly tough, which is why nuts are so satisfyingly crunchy. But this also means that some of the nutrients—especially the fats—are locked inside the cells where our digestive system can’t always break all of them free. If you eat nuts that are chopped up or that are ground into almond butter, you’re getting pretty much all the good stuff. But whole nuts often leave your body with many of their nutrient-containing cells still intact.

I think you see where we’re going with this. In a series of recent experiments, researchers from the USDA had people eat certain diets with and without nuts. They dried and burned the food these people ate, and then they did the same with their poop to figure out how many calories were still left over after digestion.

The experiments were more detailed than this, but that’s the basic idea. Participants had to store all their urine and faeces in a cooler in between trips to the lab. Thank you, brave souls, for doing your part for science.

What does this mean for me, a nut lover?

The results: cashews have 16% fewer calories than previously thought, walnuts have 21% fewer, and almonds have 32% fewer.

An interesting detail, if you read the studies, is that not everybody extracted the same number of calories from the nuts: while a serving of cashews was determined to have 137 calories, that’s an average—one person got 105 calories from a single serving, while another got 151. Every body is different, and that’s a reminder that calorie counting is never going to be precise (for this and several other reasons).

So if you eat whole nuts, they’re not quite as high calorie as you probably thought. That’s handy to know if you’re tracking calories and you eat nuts by the bowlful.