Ultra-processed foods drive obesity and metabolic risks

By Vijay Kumar MalesuReviewed by Susha Cheriyedath, M.Sc.Nov 18 2024

Discover how ultra-processed foods fuel obesity and metabolic risks, and why embracing a Mediterranean diet could turn the tide on rising health challenges.

Study: A Close Relationship Between Ultra-Processed Foods and Adiposity in Adults in Southern Italy. Image Credit: Rimma Bondarenko / Shutterstock

In a recent study published in the journal Nutrients, a group of researchers in Italy investigated the relationship between ultra-processed foods (UPFs) consumption, obesity, and adiposity measurements among adults in Southern Italy.

Background

Obesity is a global public health challenge, with food processing playing a key role in its rise. Modern food systems have shifted diets toward energy-dense UPFs, which are highly palatable, nutrient-poor, and calorie-rich. Identified by the NOVA classification, UPFs include snacks, soft drinks, and processed meats linked to increased obesity rates. While studies suggest a strong association between UPF consumption and obesity, the limitations of observational studies, including reliance on survey tools not designed to assess food processing, necessitate further research. These studies often rely on simplistic measures like body mass index (BMI), highlighting the need for more robust methods to better understand their impact on health.

About the study

The present study was conducted at the Outpatients Clinic of the I.P. “Diet Therapy in transplantation, renal failure, and chronic pathology,” University of Naples Federico II. Data were collected from 175 participants aged 18-65 with a BMI ≥30 kg/m², recruited between October and December 2021. Participants were stratified into three BMI-based groups: Class I obesity (BMI 30-34.9 kg/m²), Class II obesity (BMI 35-39.9 kg/m²), and Class III obesity (BMI ≥40 kg/m²). Exclusion criteria included bedridden status, pregnancy, cancer, dementia, depression, lactation, diabetes, or neurological disorders.

Anthropometric measurements, including weight, height, and waist circumference, were collected following standardized protocols. Body composition was assessed using bioelectrical impedance analysis, and subjects adhered to pre-measurement conditions, including fasting and avoiding caffeine or physical activity. Additionally, biochemical parameters such as triglycerides, HDL cholesterol, and the triglyceride-to-HDL ratio were evaluated as markers of insulin resistance. Blood pressure was measured following European Society of Cardiology (ESC) guidelines.

Nutritional assessments employed the PREvención con DIetaMEDiterránea (PREDIMED) and NOVA Food Frequency Questionnaires (NFFQ) to evaluate Mediterranean diet adherence and UPF consumption. Adiposity was analyzed using indices like waist-to-height ratio (WHtR), lipid accumulation product (LAP), visceral adiposity index (VAI), and cardiometabolic index (CMI). Statistical analysis was conducted using SPSS, with significance set at p < 0.05.

Study results

A total of 175 participants, 36% of whom were male, with a mean age of 43.3 ± 12.6 years and a BMI of 42 (95% CI: 37-47), were analyzed to assess eating habits in relation to BMI. Most participants were married and had attended high school, with no statistically significant differences in socio-demographic characteristics, physical activity, or education level across BMI groups. However, individuals with higher BMI values were more likely to reside in small to medium-sized cities compared to those in the lowest BMI group, who predominantly lived in metropolitan areas (p < 0.05).

UPF consumption increased significantly with BMI, both in percentage and absolute terms. In Group 1, UPF consumption accounted for 18.2% (95% CI: 16.7-23.5), compared to 26.2% (95% CI: 26.6-32.5) in Group 3 (p < 0.01). Daily UPF intake rose from 274.2 g/day (95% CI: 241.5-495.5) in Group 1 to 526.2 g/day (95% CI: 575.9-802.8) in Group 3 (p < 0.001). Soft drinks emerged as the predominant contributor, with consumption more than doubling in Group 3 compared to Group 1 (p < 0.01). Higher BMI groups also demonstrated increased consumption of sweets and chips, sausages, savory snacks, ice cream, and nuggets (p < 0.05 to p < 0.001), while consumption of MPFs decreased significantly as BMI increased (p < 0.001).

Mediterranean diet (MD) adherence was poor across all BMI groups, with a significant decline observed as BMI increased. Group 3 participants had a PREDIMED score of 5 (95% CI: 4.8–5.3), reflecting lower MD adherence compared to Groups 1 and 2 (p < 0.005).

Further analysis divided participants into tertiles based on UPF consumption, revealing a significant trend of younger participants in the highest UPF tertile (p < 0.05). Higher UPF consumption was associated with elevated adiposity indices, including WHtR, VAI, LAP, CMI, and Waist Triglyceride Index (WTI) (p < 0.001). WHtR increased from 0.6 (95% CI: 0.6-0.7) in T1 to 0.7 (95% CI: 0.7-0.8) in T3. VAI and LAP values rose significantly, with the latter increasing from 80.4 (95% CI: 65.9-91.4) in T1 to 113.6 (95% CI: 95.3-129) in T3. These findings highlight a clear association between higher UPF consumption and adverse adiposity-related outcomes.

Conclusions

To summarize, this study reveals a positive association between UPF consumption and obesity, with increased UPF intake linked to higher adiposity indices and reduced adherence to the MD. Soft drinks were the primary contributors, with their consumption rising alongside BMI, followed by processed snacks and ready-to-eat meals. The hyper-palatability, high energy density, and additives in UPFs may promote overeating, visceral fat accumulation, and metabolic disturbances. Additionally, the study emphasizes the higher cardiometabolic risks observed in participants with elevated WHtR and VAI indices. Elevated indices such as WHtR and VAI in high UPF consumers highlight increased cardiometabolic risk.

The authors note limitations, including the retrospective nature of the study and the lack of assessment for stress levels and sleep quality, which may influence adiposity outcomes. These findings underline the need for public health strategies to promote traditional diets like the Mediterranean diet and to limit UPF intake as part of obesity prevention efforts.