Highly processed foods contribute to poor diet quality among Japanese adults

In a recent study published in the journal Public health nutritionresearchers explore intake of highly processed foods (HPF) versus overall diet quality.

Study: Consumption of highly processed foods in relation to overall dietary quality among Japanese adults: A nationwide study.  Image credit: Ilia Nesolenyi/Shutterstock.com Study: Highly processed food consumption in relation to overall diet quality among Japanese adults: A nationwide study. Image credit: Ilia Nesolenyi/Shutterstock.com

What are HPFs?

In recent years, various epidemiological studies have explored the health outcomes related to the consumption of HPF. Meta-analysis data indicate that HPF intake is linked to overweight or obesity, as well as the development of heart disease, metabolic syndrome, cerebrovascular disease, depression, and death.

Compared to non-HPFs, HPFs are associated with an unhealthy nutritional profile due to their higher contents of total fat, trans fat, saturated fat, sodium and free sugar, along with their lower contents of protein, vitamins, fiber and minerals. Therefore, the consumption of HPF, particularly in high quantities, can reduce the quality of the diet.

About the studio

In the present study, researchers evaluate the association between HPF intake and diet quality among Japanese adults.

Dietary information from a national survey conducted from February to March 2013 was used for the current analysis. A total of 388 people, which included 196 men and 192 women, respectively, participated from different regions in Japan.

A four-day dietary record (DR) was used to obtain insights into the participants’ eating habits. Participants were asked to document everything they ate and drank for four consecutive days, which involved weighing all foods and drinks during the study period.

The names of the dishes were also recorded, whether the dishes were prepared at home, away from home or elsewhere, the names of the ingredients found in the dishes, and the estimated quantities or weights of the foods that were consumed.

Using the University of North Carolina at Chapel Hill (UNC) method, all foods mentioned in the DR were classified as minimally processed or unprocessed, basic processed, moderately processed, and highly processed. Standard Tables of Food Composition in Japan (STFCJ) were used to determine the amount of energy and nutrients consumed by each person over a four-day period based on the nutritional value and weight of each food item.


The mean age of the study cohort was 44.5 years, while their mean body mass index (BMI) was 23.3 kg/m2. When home cooked meals were broken down by food group, grains and starchy foods contributed the most to overall HPF energy expenditure, followed by fish, meat, eggs, sweets, fats and oils, and alcoholic beverages. When food-level grouping was used, these food groups were among the top five largest energy consumers.

When meals cooked away from home were placed in the dish category instead of the food category, they brought in much more energy. Comparatively, for unprocessed or minimally processed, basic processed, and moderately processed foods, plate-level classification provided much smaller estimates of energy contributions than food-level classification. There was a strong link between the energy contributions of foods in each plate- and food-level processing group.

The mean amount of energy consumed did not change between tertile groups; however, the average amount of some food groups has changed. For example, people in the upper tertiles ate fewer grains and starchy foods, vegetables, fruits, legumes, fish, meat and eggs, but more sweets, alcoholic beverages, condiments and spices, oils and fats.

The mean Healthy Eating Index-2015 (HEI-2015) score was 51.1, while the mean Nutrient-Rich Food Index 9.3 (NRF9.3) score was 621.9.

For dish- and food-level classifications, participants in the highest tertiles of HPF energy intake showed reduced HEI-2015 component and total scores with respect to total greens, beans, greens, added sugars, added sugars, and foods total protein, and higher scores for refined grains. Additionally, when plate-level categorization was used, only those in the top tertiles scored lower for saturated fat.


Approximately one-third of all energy consumed by study participants was provided by HPFs. Importantly, the higher amount of energy in the HPFs was linked to a lower quality diet, whether or not home-cooked dishes were sorted into their individual ingredients before being grouped according to the level of preparation of the food.

These results indicate that reducing HPF consumption could be an effective public health strategy to improve the quality of diets. However, more research is needed to develop effective programs and policies to improve Japanese diet quality in relation to HPF reduction.

Magazine reference:

  • Shinozaki, N., Murakami, K., Asakura, K., et al. (2023). Highly processed food consumption in relation to overall diet quality among Japanese adults: A nationwide study. Public health nutrition; 1-33. doi:10.1017/S1368980023000721

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