High consumption of ultra-processed food associated with increased body fat, particularly in the abdomen

By Pooja Toshniwal PahariaReviewed by Benedette Cuffari, M.Sc.Mar 26 2023

In a recent study published in the American Journal of Preventive Medicine, researchers evaluate the effects of high ultra-processed food (UPF) consumption on the distribution of body fat among adults in the United States.

Study: Consumption of Ultraprocessed Foods and Body Fat Distribution Among U.S. Adults. Image Credit: margouillat photo / Shutterstock.com

Background

UPFs are extensively consumed by U.S. residents and contribute to over 50% of the daily calories consumed. UPFs are rich in salt, refined sugars, and starch, and have poor nutritional values, lacking healthy components. Diets with high UPF content have been related to increasing weight, diabetes mellitus type 2, obesity, cardiovascular diseases, and cancer.

Previous studies on UPFs have been conducted using body mass index (BMI) values and waist circumference to assess obesity. However, these measurements are affected by body size, muscle mass, ethnicity/race, and socioeconomic conditions.

Body fat distribution appears to be more specific in estimating disease risks. However, the relationship between UPF intake and the distribution of body fat, as well as the influence of sociodemographic variables on this relationship, is not clear.

About the study

In the present cross-sectional study, researchers assess the association between UPF intake and body composition.

The study was conducted between September 2022 and January 2023, comprising 9,640 male and female individuals between 20 and 59 years of age. Study participants were recruited from four consecutively performed National Health and Nutrition Examination Surveys (NHANES). All individuals had valid one-day diet recalls and full-body g dual-energy X-ray absorptiometry scans.

Food items were identified as ultra-processed based on the NOVA framework, whereas the percent energy obtained from UPFs was expressed as quintiles. The prime study outcomes were the total percent fat, gynoid percent fat, and android percent fat. Secondary study outcomes included percent fat in the trunk, legs, arms, and head, visceral-type adipose tissues (VAT), subcutaneous AT (SAT), and total abdominal fat (TAF).

Multivariable linear regression modeling was performed for the analysis, with data adjustments for covariates such as lifestyle and sociodemographic factors including age, sex, ethnicity, race, level of education, smoking habits, physical exercise, and income Covariate data obtained through standardized questionnaires.

Exploratory analyses were performed for the relationship between UPF intake and the prime study outcomes, stratified by subgroups of gender, age, ethnicity/race, income and education. Pregnant females were excluded from the analysis.

Results

The mean participant age was 39 years, with 49% of the sample population being female. UPF intake was accountable for 56% of the regular caloric intake of the sample population.

In comparison to individuals in the lowermost quintile of less than 39% energy of UPF intake, those in the uppermost quintile with greater than 72% energy of UPF intake had greater percentage points for total fat, android fat, and gynoid body fat content by 1.6, 2.1, and 1.3, respectively.

Similar patterns were observed for the associations between UPF intake and the secondary study outcomes. For example, individuals belonging to the uppermost quintile of UPF consumption had greater percentage points for percent fat in the arms, legs, and trunk by 1.7, 1.3, and 1.9, respectively.

Adult individuals in the uppermost quintile of UPF intake had 54 cm² greater TAF area, 259 g greater TAF mass, 280 cm³ greater TAF volume, 44 cm² greater SAT area, 212 g greater SAT mass, 229 cm³ greater SAT volume, 9.8 cm² greater VAT area, 47 g greater VAT mass, and 51 cm³ greater VAT volume. The relationships between UPF intake and prime study outcomes were comparable for the majority of subgroups stratified by gender, age, income, and education.

Among individuals in the uppermost quintile of UPF intake, in comparison to those in the lowermost quintile, the total percent fat was greater by 1.9 and 1.6 among non-Hispanic Whites and Hispanics, respectively. The corresponding differences in gynoid percent fat among non-Hispanic Whites and Hispanics were 1.7 and 1.1, respectively. Exploratory analyses indicated that UPF intake was less related to the composition of body fat among non-Hispanic Asians and Blacks than among Hispanics and among non-Hispanic Whites.

In comparison to low UPF diet consumers, high UPF diet consumers were younger, non-Hispanic Whites or Blacks, less educated, with lower income, and smoking habits. UPF consumption showed a U-shaped association with exercise.

Conclusions

Mechanisms for an increase in body fat mass due to high UPF intake include faster UPF consumption, high glycemic index (GI) of UPFs, and thorough UPF digestion in the gastrointestinal tract. This led to reduced nutrition for microbiota of the large intestine and greater proportions of caloric consumption by hosts versus their microbiomes.

Artificial additive substances in UPFs may also affect the intestinal microbial balance, glycemic responses, satiety and/or hunger. The lack of particular phenolics, prebiotics, and other bioactive substances in UPFs that protect against obesity may contribute to the increase in body fat. Moreover, obesogenic substances in food processing and packaging may disrupt the production, secretion, transport, and activity of hormones regulating appetite and metabolism.

Overall, greater UPF intake was related to increased body fat, particularly android fat. Further research must be conducted using interventional, mechanistic, and prospective study designs to evaluate the effects of UPF consumption on the distribution of body fat and obesity in various populations.