The science of energy density and satiety

What is energy density?

Energy density refers to how many calories a food has per gram or ounce. Foods with high energy density have lots of calories packed into a given weight of food. Foods with low energy density offer few calories in the same weight of food.

For example, potato chips, donuts, and oils have high energy density. You don’t have to consume many grams or ounces of these foods to get a lot of calories.

Asparagus and broccoli have low energy density. It takes a large amount to provide a lot of calories. When you eat a lot of asparagus and broccoli, you’ll fill up your stomach and get plenty of nutrients without ingesting many calories. 

Foods with low energy density tend to have more water, more fiber, and less fat.

Foods with high energy density tend to have low levels of water and fiber and more fat.

Multiple studies report that lower-energy-density diets correlate with improved satiety and weight loss compared to higher-energy-density diets. Part of the improved satiety and weight loss may be directly related to the lower-energy-density foods being higher in fiber and water and lower in starch, sugar, and fat.

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The science supporting foods with a lower energy density

One study back in 1983 demonstrated that people who ate foods with a lower energy density ate half as many calories as those who ate foods with a higher energy density. Participants who ate foods with a lower energy density also took 33% longer to finish their meal, so some question whether the difference in calorie intake was caused by the eating time or the energy density.

In truth, it may not matter. The slower pace of eating foods with a lower energy density happens naturally, without purposely trying to do it. Compare that to trying to eat a donut or bag of potato chips slowly. That’s hard to do!

Other mechanisms of lower-energy-density foods’ beneficial effects are reduced feelings of hunger and increased satiety.  In the study discussed above, participants reported decreased cravings and greater control over eating.

Multiple randomized trials and observational studies support the idea that eating foods with a lower energy density reduces calorie intake despite higher food volume. However, as one study reported, the beneficial effects of lower energy density on satiety likely apply to solid foods but not to liquids.

Foods with higher energy density also tend to be more palatable. Therefore, a food’s taste could be part of the driving force to eat more, which suggests there may be multiple reasons for excess intake and weight gain.

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Energy density and ketogenic diets

Some experts question whether this research on energy density applies to all dietary patterns, regardless of the macronutrient composition. 

One systematic review of studies that manipulated energy density found that eating foods with a lower energy density led to eating fewer calories. This relationship was true across a range of macronutrients. However, as with many energy density studies, the authors did not evaluate very low carb diets. 

Could ketogenic diets be the exception? Unfortunately, comparing a low-energy-density keto diet to a high-energy-density keto diet hasn’t been studied with trials of sufficient length to allow for adaptation and provide a reliable answer.

But long-term studies of ketogenic diets report reduced calorie intake and increased weight loss, despite allowing unrestricted amounts of butter, oils, high fat dairy, and other foods with high energy density. So the power of energy density to affect the number of calories consumed may be blunted by keto.

Putting it all together

As we previously mentioned, we use satiety to encompass:

Eating low-energy-density foods may help with satiation and short-term satiety.

This hypothesis makes sense, practically. Eating a whole plate of spinach and asparagus may make you feel full fairly quickly (from the food volume and stomach expansion). But your calorie and protein intake would be deficient — factors that may drive hunger over the longer term. Once the food volume is out of your stomach, and the stretch receptors are no longer triggered, hunger may return.

But some studies suggest that as long as you continue to eat low-energy-density foods, you tend to eat less over time and lose weight. We believe this is more likely to be the case when you combine low-energy-density foods with higher protein foods. Adding protein to food with a low energy density adds calories and nutrients, and will likely help with longer-term satiety. 

So, although a specific characteristic of a food, like energy density, may help with satiety, combining low energy density with high protein percentage, high fiber, and low hedonic factors together is likely the best approach for long-term satiety and healthy weight loss.

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