"A calorie is a calorie" - or is it?

If you’ve ever been told that “a calorie is a calorie,” you’re not alone. This phrase has become so common, it even has its own Wikipedia page. But while it’s technically true in a physics sense (more calories in than out = weight gain), it drastically oversimplifies how food really works in the human body.

Let’s use nuts to show why.

Are nuts just...magic?

A 2021 research review analyzed 55 studies involving nearly 4,000 participants who were asked to eat about 300 calories’ worth of nuts daily.⁽¹⁾ Some were told to swap nuts in for other foods. Others were just told to “add nuts” with no other changes.

The results? Nobody gained weight—not even the group that added calories on top of their usual intake. That’s not what standard calorie math would predict.

Here’s why the math doesn’t match real life:

• Nuts increase satiety – The combo of healthy fats, fiber, and protein helps you feel full longer, naturally reducing how much you eat later.

• They boost metabolism – Whole foods like nuts require more energy to digest (a process called thermogenesis), meaning you burn more calories just breaking them down.

• Not all calories are absorbed – Nuts contain compounds that block full absorption of their calories. Some of what you eat literally passes right through.

• They may raise resting metabolic rate – The body may burn more energy overall in response to nutrient-dense foods like nuts.

  
  

In other words, your body responds differently depending on what you eat—not just how much.

💡 What this means for your diet:

If you enjoy nuts, there’s no reason to avoid them. They’re nutrient-dense, satisfying, and can help reduce cravings for more processed snacks. But like anything else, moderation still matters. This isn’t a green light to eat a jar of peanut butter with a spoon (don’t pretend you haven’t been tempted 😉).

Bottom line: Calories matter, but where they come from matters more. Real food always wins.

References

1. Guarneiri, Liana L., and Jamie A. Cooper. 2021. “Intake of Nuts or Nut Products Does Not Lead to Weight Gain, Independent of Dietary Substitution Instructions: A Systematic Review and Meta-Analysis of Randomized Trials.” Advances in Nutrition (Bethesda, Md.) 12 (2): 384–401.