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According to new research, there are three top factors that contribute to caloric intake at mealtime. Image credit: Carol Yepes/Getty Images
  • Researchers investigated the effects of different meal characteristics on caloric consumption.
  • They found that meals that are eaten quickly and that contain high-energy density, as well as highly palatable foods are linked to higher caloric intake across four diets.
  • They noted that further research is needed to confirm their findings.

The rate of obesity worldwide has almost tripled since 1975. Between 2017 and 2022, obesity affected 41.9% of the United States population.

The main cause of obesity is long-term energy imbalance — consuming more calories than the body gets a chance to burn. Research into dietary practices for weight loss is thus key for treating obesity.

Studies have shown that eating quickly and higher energy density foods — foods that have more calories per gram — is linked to greater food intake. Other data have shown that highly palatable foods may be artificially rewarding to consume.

Meanwhile, higher protein intake has been linked to increased satiety and lower energy intake. Understanding more about key dietary characteristics could aid the design of diets to treat obesity.

Recently, researchers investigated how meal characteristics affect caloric intake in four different dietary patterns.

They found that meal energy density, how quickly meals were eaten, and consumption of hyper-palatable foods influenced caloric intake.

The new study appears in Nature.

The researchers analyzed data collected from 35 individuals who participated in two inpatient feeding studies. All participants were aged between 18 and 50 years and had a stable weight for the previous 6 months.

During the studies, they were exposed to either minimally processed diets, which varied widely in carbohydrate and fat content, or diets with moderate levels of carbohydrate and fat that varied in ultra-processed and minimally processed foods.

Participants were exposed to two different diets with 7-day rotating menus for two weeks each. They were asked to eat as much as they wanted from each dietary condition.

All in all, the researchers had complete data for 2,733 meals, including their energy density, protein content, speed of eating, and percentage of hyper-palatable foods consumed- defined as those high in fat, sodium, fat, and sugar, or high in carbohydrate or salt.

In the end, the researchers found that energy density, percentage of highly palatable foods consumed, and eating rate all correlated with increased energy intake across all diets: low-fat, low-carbohydrate, a diet based on unprocessed foods, and a diet based on ultra-processed foods.

They found, however, that higher protein intake correlated with increased energy intake only in unprocessed and ultra-processed diets with moderate levels of carbohydrates and fat.

They further found that previous meal protein consumption was linked to greater energy intake in subsequent meals in the low-fat and low-carbohydrate diets, but reduced intake during the ultra-processed diet.

The researchers wrote that their findings suggest that energy density, eating rate, and percentage of protein and highly palatable foods consumed are important predictors of energy intake.

To understand how higher energy density foods might increase caloric intake, MNT spoke with Dr. Dana Ellis Hunnes, assistant professor at UCLA Fielding School of Public Health, who was not involved in the study.

“Energy density means how many calories are [in] a certain amount of food,” she explained. “The higher the energy density of something, the less of it you need to take in to have [a] higher calorie intake. For example, one tablespoon of peanut butter has roughly 100 calories in it versus one tablespoon of cooked oats has 15 calories.”

Kimberly Spatola, a registered dietitian at Novant Health Heart and Vascular Institute in Charlotte, NC, not involved in the study, also told MNT:

“Hyper-palatable foods also tend to be energy dense and higher in refined carbohydrates, which make it easier to eat a large amount of these foods without being truly satisfied. Speed of eating can also make a big difference in how much you eat. It typically takes about 20 minutes for the fullness signals from our stomach to reach our brain. Therefore, if you are eating a large meal in only 10 minutes, it will take some time before you actually register your fullness cues.”

When asked about the study’s limitations, Dr. Kevin Hall, section chief of integrative physiology at the National Institute of Diabetes and Digestive and Kidney Diseases at the U.S. Department of Health and Human Services, the senior author of the study, told MNT that “[t]he study is limited by the fact that it was a secondary analysis of previously published feeding trials in inpatient research participants housed at the Metabolic Clinical Research Unit at the NIH Clinical Center.

“While this environment allowed for accurate and precise measurements of food intake and provided excellent control over the food environment, it is difficult to know how our results extrapolate to more natural environments,” he cautioned.

Spatola added that the findings might also be limited due to their small patient sample size.

“Also the adults were all relatively young with the mean age being 29-31 years old, [and] fiber intake was not taken into consideration, which can greatly affect energy density consumed. […] More research would be needed to see if the patterns are consistent among other age groups,” she continued.

Dr. Hunnes explained: “As with anything in nutrition, one implication would be to consume a widely varied diet to get a wide range of caloric-density foods — such as low density from broths and salads, and high density from foods like nuts. Another implication of these findings would be that eating slowly is beneficial in terms of regulating overall calorie intake as is eating the least-processed/unprocessed foods possible.”

“When we eat unprocessed/ least-processed foods, we are getting a lot more water from the food- think fruit or vegetable rather than ‘veggie-flavored crackers,” she added.

“So, when we eat foods that are unprocessed, we eat fewer calories, and they are less calorically dense. These things all matter in terms of eating! A whole-food, plant-based diet fits this bill very nicely.”