Calorie counts are everywhere: stamped on packaged foods, plastered on restaurant menu boards, and accompanying recipes in magazines. They’re inescapable. And many of us pay a great deal of attention to these numbers in the name of calorie-controlled eating.
In recent years, however, scientific studies have cast doubt on the way calories in some foods are measured and how we typically count them.
You see, calorie stats are based on a century-old formula called the Atwater system, where the macronutrient components — carbohydrate, fat and protein — of a food have a set number of calories (a unit of energy). But this fails to tell the whole picture regarding the calories you actually extract from foods.
“When it comes to the way we metabolize calories, the types of foods we eat has a big impact on this,” says Megan Hilbert, a registered dietitian nutritionist with Top Nutrition Coaching.
Calorie absorption and metabolism are more complex than we may think.
Here are a few ways you can tweak your diet to help eat your way to a calorie deficit, or at least make it harder to go overboard on them.
Nuts are not a low-calorie food, but a few studies have shown we metabolize (absorb) fewer of their calories than once thought. For instance, an investigation in the journal Nutrients found that we typically glean about 16 percent fewer calories from cashews than what you would read on nutrition labels.
“Because available energy in whole foods like nuts is behind cell walls, we often don’t absorb every last calorie, and thus, this energy gets expelled in our stool,” Hilbert explains.
Microorganisms in our gut microbiome also get access to some of the calories in almonds and other nuts, which may help explain why studies have failed to show that eating calorie-dense nuts leads to weight gain. With the extra processing that breaks down the nuts’ cell walls, there is a good chance we absorb more calories from nut butter than whole nuts.
When you cook starchy foods like rice and potatoes and then let them cool down in the refrigerator for several hours a unique type of carb called resistant starch is formed.
“This is a carbohydrate that our digestive system can’t break down into energy and instead becomes food for our gut bacteria,” notes Hilbert. “Research shows that resistant starch has fewer calories than regular starch — two instead of four calories per gram.”
So, a cold potato salad or grain salad is likely to have less digestible calories than if you eat these foods immediately after cooking them. Ditto for green-skinned bananas which have more resistant starch than ripe bananas.
In general, eating more high-fiber foods like legumes and seeds is a good way to bid adieu to more calories.
“Higher fiber foods take longer to digest and thus, we don’t get the available energy from these foods as easily,” Hilbert explains.
Different foods go through different metabolic pathways. Some of these pathways are more efficient than others.
“Protein takes the most energy to digest compared to the other macronutrients and 20% to 30% of the total calories from protein are used to digest it,” says Hilbert, who adds: “The reason for this is that proteins are large and complex molecules that take a lot of moving parts to properly break them down.”
Owing to the abundance of protein, the calories we derive from a chicken breast, a slab of beef, or bowl of Greek yogurt is likely less than advertised on the label.
Extra calorie burn may be one way that higher protein diets help some people drop pounds.
According to Hilbert, intact whole grains like wheat, rye, barley, oats, quinoa and spelt have most of their available calories packaged behind cell walls and fibers which makes those calories harder for our bodies to digest and absorb.
“If we think about the act of processing foods, such as turning grains into flour, this is partially digesting those foods for us and because of this, we can absorb more of the calories.”
So, anything that reduces the size of food particles in items like whole grains likely increases the calories you absorb from that food. Cooking flour (in pasta, bakery products, and so forth) likely increases the calories you absorb even more.
A study published in the American Journal of Clinical Nutrition found that people who consumed a diet rich in whole grains burned almost 100 more calories per day than those who ate the same diet but with refined grains such as white flour and white rice, due to a greater resting metabolic rate and the excretion of more calories.
Soaking up more calories from ultra-processed foods might be a way that they can contribute to unwanted weight gain.
An investigation in the journal Food & Nutrition Research provided volunteers with either a sandwich made with multigrain bread and cheddar cheese or one made with more highly processed white bread and cheese slices.
Even though both meals had the same number of total calories on paper, the less-processed sandwich meal required nearly twice as much energy to digest resulting in fewer calories being available to the body for storage.
Again, the added work required for the digestive process and the extra fiber present in the less-processed sandwich could drive up the calorie burn and drive down the calorie absorption.
Other research shows that people simply tend to consume more calories when eating ultra-processed foods than calories from minimally processed foods.
So, a combo of higher calorie intake and more calorie retention can make ultra-processed food problematic for achieving a healthy body weight.
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