Calorie counts are everywhere: they’re listed on food packages, on restaurant menus, and in recipe magazines. They’re inescapable. And many of us pay close attention to those numbers in the name of calorie-controlled eating.
In recent years, however, scientific studies have cast doubt on how the calories of certain foods are measured and how we usually count them.
Calorie statistics are based on a centuries-old formula called the Atwater system, which states that the macronutrient components (carbohydrates, fats, and proteins) of a food have a set number of calories (a unit of energy). But this doesn’t give a complete picture of the calories you’re actually extracting from food.
“When it comes to how we metabolize calories, the types of foods we eat have a big impact on that,” says Megan Hilbert, a registered dietitian nutritionist at Top Nutrition Coaching.
Calorie absorption and metabolism are more complex than you might think.
Here are some ways you can modify your diet to help you achieve a calorie deficit, or at least make it harder to overindulge.
Go crazy for whole nuts
Nuts aren’t a low-calorie food, but several studies have shown that we metabolize (absorb) fewer calories than previously thought. For example, a study published in the journal Nutrients found that we typically absorb about 16% fewer calories from cashews than what nutrition labels suggest.
“Because the energy available in whole foods like nuts is behind cell walls, we often don’t absorb every calorie and, as a result, that energy is expelled in our stool,” Hilbert says.
The microorganisms in our gut microbiome also have access to some of the calories in almonds and other nuts, which may explain why studies have failed to show that eating high-calorie nuts causes weight gain. With the extra processing that breaks down the cell walls of nuts, there’s a good chance we’re getting more calories from nut butter than from whole nuts.
Cool your carbs
When you cook starchy foods like rice and potatoes and then let them chill in the refrigerator for several hours, a unique type of carbohydrate called resistant starch is formed.
“It’s a carbohydrate that our digestive system can’t turn into energy and instead becomes food for our gut bacteria,” Hilbert notes. “Research shows that resistant starch has fewer calories than regular starch: two calories per gram instead of four.”
So, a cold potato salad or grain salad is likely to have fewer digestible calories than if you eat it immediately after cooking it. The same goes for green-skinned bananas, which contain more resistant starch than ripe bananas.
In general, eating more high-fiber foods, like legumes and seeds, is a good way to say goodbye to calories.
“High-fiber foods take longer to digest, and as a result, we don’t get the energy available from these foods as easily,” Hilbert says.
Increase protein consumption
Different foods go through different metabolic pathways. Some of these pathways are more efficient than others.
“Protein requires more energy to digest than other macronutrients, and 20 to 30 percent of total calories from protein are used to digest it,” says Hilbert, adding, “This is because proteins are large, complex molecules that require many moving parts to be properly broken down.”
Because of the abundance of protein, the calories we get from a chicken breast, a slice of beef or a bowl of Greek yogurt are likely lower than what the label claims.
Burning extra calories may be one way high-protein diets help some people lose weight.
Keep your grains (more) whole
According to Hilbert, most of the available calories in intact whole grains like wheat, rye, barley, oats, quinoa and spelt are stored behind cell walls and fiber, making these calories more difficult for our bodies to digest and absorb.
“If we think about the act of processing food, like turning grains into flour, it’s partially digesting that food for us, and because of that we’re able to absorb more calories.”
So anything that reduces the size of food particles in foods like whole grains likely increases the calories you absorb from those foods. Baking flour (in pasta, baked goods, etc.) likely increases the calories you absorb even more.
A study published in the American Journal of Clinical Nutrition found that people who ate a diet rich in whole grains burned nearly 100 more calories per day than those who ate the same diet but included refined grains like white flour and white rice, due to a higher resting metabolic rate and excretion of more calories.
Limit ultra-processed foods
Eating more calories from ultra-processed foods could be one way to contribute to unwanted weight gain.
A study published in the journal Food & Nutrition Research provided volunteers with either a sandwich made with multigrain bread and cheddar cheese or a sandwich made with slices of highly processed white bread and cheese.
Even though both meals contained the same total number of calories on paper, the less processed sandwich required nearly twice as much energy to digest, leaving fewer calories available for the body to store.
Again, the extra work required for the digestive process and the extra fiber present in the less processed sandwich could increase calorie burning and decrease calorie absorption.
Other research shows that people simply tend to consume more calories when eating ultra-processed foods than calories from minimally processed foods.
Thus, a combination of higher caloric intake and greater caloric retention may make ultra-processed foods problematic for achieving a healthy body weight.
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