Ultra-processed foods linked to increased obesity risk in preschoolers

By Dr. Liji Thomas, MDReviewed by Lily Ramsey, LLMFeb 4 2025

Study finds higher UPF consumption in early childhood correlates with increased body fat, especially in boys.

Study: Ultraprocessed Food Consumption and Obesity Development in Canadian Children. Image Credit: Rimma Bondarenko/Shutterstock.com

Across much of the world, processed "fast" foods have replaced traditionally prepared meals made from minimally processed ingredients. This shift has coincided with rising obesity rates.

A recent study published in JAMA Network Open explores the connection between ultraprocessed food (UPF) consumption and obesity in Canadian preschoolers.

The risks of UPF

Ultra-processed foods are highly processed, prepackaged products made from food extracts and additives rather than whole foods. While they offer convenience, they also tend to be high in salt, sugar, and saturated fats, encouraging overconsumption. When these foods make up a significant portion of daily intake, they can contribute to chronic health issues.

A Canadian study found that over half of children and adolescents' daily energy intake came from UPFs. Similarly, adults with a high UPF intake face a greater risk of obesity. In 2020, 8.3 million Canadian adults were classified as obese—an increase of one million in just two years.

One in three Canadian children and adolescents are overweight or obese, with boys being more affected. However, research on UPF’s role in childhood obesity has yielded mixed results.

Obesity in early childhood (before age four) has long-term health implications, but diet remains a modifiable risk factor. This study sought to examine the link between UPF consumption and body fat in preschoolers, with the goal of informing public health policies aimed at prevention.

Study overview

The study included 2,217 children from the CHILD Cohort Study, one of Canada’s largest multicenter prospective studies initiated during pregnancy. Researchers assessed the children's diets via questionnaires at a median age of three years and measured body mass parameters at age five.

On average, UPFs accounted for 45% of daily energy intake—46% in boys and 44% in girls. Across the cohort, higher UPF consumption was positively associated with increased body fat, including a higher body mass index (BMI) and greater fat accumulation, as measured by subscapular and triceps skinfold thickness.

When analyzed by sex, the patterns differed. In boys, every 10% increase in UPF consumption correlated with:

• A 0.08 increase in BMI
• A 0.07 increase in waist-to-height ratio (WHR)
• A 0.12 increase in subscapular skinfold thickness
• A 0.09 increase in triceps skinfold thickness

Even after adjusting for BMI at age three, these associations remained significant in boys. In contrast, no such correlations were observed in girls.

While UPF consumption did not significantly raise obesity or overweight rates in the entire cohort, boys were 19% more likely to be overweight or obese for every 10% increase in UPF intake. No similar link was found in girls.

These findings align with previous research showing that young children derive 40%-50% of their energy from UPFs.

Unlike prior studies with inconsistent results—possibly due to a lack of sex-specific analysis—this study clearly demonstrates that boys are more prone to weight gain and fat accumulation from UPF consumption than girls.

This is the first large-scale study to explore the relationship between UPF intake and childhood obesity while also highlighting differences in boys' and girls' responses to UPFs.

Why does UPF contribute to obesity?

Several factors may explain the link between UPF consumption and obesity. These foods are highly palatable and energy-dense, making them easy to overconsume. However, even when controlling for calorie intake, the association with obesity persists.

UPFs contain emulsifiers and additives that may alter gut microbiome composition, affecting digestion and nutrient absorption. Similar findings have been observed in adults, with sex-specific differences also emerging in some studies.

Additionally, boys tend to consume more calorie-dense foods and store fat differently than girls. Males are more likely to accumulate fat in the abdominal region—both under the skin and around internal organs—whereas females store more fat in the thighs and gluteal area.

Future research should further investigate these differences by examining total and regional fat distribution.

Key takeaways

The study concludes that "high UPF consumption during early childhood was associated with obesity development, primarily in males." This highlights the need for targeted public health policies.

Childcare providers and caregivers should be educated on the importance of providing nutritious foods and minimizing UPF intake to support children’s long-term health.

Policies promoting clear labeling on UPF packaging should continue alongside new initiatives aimed at fostering healthy eating habits in young children. Future studies should refine UPF classification and further investigate how physiological responses to UPF ingredients contribute to childhood obesity.

Encouraging healthier food choices from an early age is crucial in addressing childhood obesity and promoting lifelong well-being.