How strong is the link between ultra-processed foods and obesity?
The connection is robust and consistent across many types of studies. A 2023 meta-analysis of 17 studies found that people who consumed the most ultra-processed foods had a 65% higher odds of being obese compared to those who consumed the least [1][6]. This means that if you eat a diet high in these foods, your risk of obesity is about one and a half times greater. Another study in Brazil showed that between 2002 and 2009, as ultra-processed food consumption rose from 14.3% to 17.3% of total calories, the increase in obesity prevalence was directly linked—over a quarter (28.6%) of the rise in obesity was attributable to this dietary shift [5].
This pattern holds across different countries and demographics. In South Korea, adults in the highest quarter of ultra-processed food intake had a 24% higher odds of obesity and a 34% higher odds of abdominal obesity [3]. A study in southern Italy found that as body mass index (BMI) increased, so did ultra-processed food consumption, while adherence to a healthy Mediterranean diet decreased [9]. The evidence is particularly strong for women: a Korean study found women with the highest intake had 51% higher odds of obesity and 64% higher odds of abdominal obesity [7]. A 2024 review of the evidence concluded that greater ultra-processed food consumption has been a key driver of obesity, supported by high-quality clinical data [10].
How do ultra-processed foods cause weight gain?
Ultra-processed foods are engineered to be overeaten. They are typically soft in texture, high in energy density (calories per bite), and combine sugar, fat, and salt in ways that override the body's natural fullness signals and stimulate reward centers in the brain [11]. This means you eat more calories before feeling full. For example, a 2025 review explains that these foods affect ingestive behaviors, satiety signaling, and food reward systems, leading to excessive energy intake [11].
Beyond just calories, these foods may disrupt metabolism in other ways. They often contain emulsifiers, non-nutritive sweeteners, and contaminants from processing and packaging that can alter gut bacteria, affect blood sugar control, and change how nutrients are absorbed [11]. A 2022 review also notes that ultra-processed foods may increase cancer risk partly through their obesogenic properties, as well as through exposure to potentially carcinogenic compounds like certain food additives [8]. This suggests the harm goes beyond simple overeating.
Importantly, the link is not just about the nutrients themselves. A 2024 review points out that the ultra-processed food concept captures something that existing nutrient- and food-based frameworks do not—the effects of industrial processing itself [10]. This means that even when you account for total calories or overall diet quality, the association with obesity remains, though it may be weakened [3]. The processing appears to have independent effects on weight.
Are there other health effects beyond obesity?
Yes, the health impacts of ultra-processed foods extend well beyond weight gain. A large Brazilian study of over 10,000 adults found that those who ate more ultra-processed foods experienced a 28% faster rate of cognitive decline over 8 years, including memory and executive function [2]. This suggests that what's bad for your waistline may also be bad for your brain.
Other studies have linked ultra-processed food intake to increased risk of colon cancer, sinusitis, and other chronic conditions. The meta-analysis that found a 65% higher odds of obesity also found a positive (though not statistically significant) link between obesity and colon cancer risk [1][6]. A 2025 study using U.S. national data found that people in the highest quarter of ultra-processed food intake had a 54% higher odds of self-reported sinusitis [4]. These findings underscore that ultra-processed foods are associated with a broad range of health problems, likely through multiple mechanisms including inflammation, metabolic disruption, and altered gut health.
About These Sources
This answer is built on 11 peer-reviewed studies — published from 2021 to 2025, 5 from 2024 or later, 9 in Q1 journals, collectively cited 392 times — selected as the most relevant from 11 studies that passed quality screening, drawn from 50 papers retrieved from a database of over 500 million.
Sources used in this answer
S432 Ultra-Processed Food, Obesity, and Colon Cancer: A Systematic Review and Meta-Analysis
A meta-analysis of 17 studies found high ultra-processed food consumption was associated with a 65% higher odds of obesity (OR 1.65, 95% CI 1.07-2.45).
Association Between Consumption of Ultraprocessed Foods and Cognitive Decline
In a prospective cohort of 10,775 Brazilian adults, those with higher ultra-processed food intake showed a 28% faster rate of global cognitive decline over 8 years.
Ultra-Processed Food Consumption and Obesity in Korean Adults
Among Korean adults, those in the highest quartile of ultra-processed food intake had 24% higher odds of obesity and 34% higher odds of abdominal obesity, though the association weakened after adjusting for total energy and diet quality.
Association Between Ultra-Processed Food Intake and Sinusitis
In a U.S. national sample of 10,068 adults, the highest quartile of ultra-processed food intake was associated with 54% higher odds of self-reported sinusitis.
Changes in Obesity Prevalence Attributable to Ultra-Processed Food Consumption in Brazil Between 2002 and 2009
In Brazil between 2002 and 2009, 28.6% of the increase in obesity prevalence was attributable to the rise in ultra-processed food consumption.
Ultra-processed food, obesity, and colon cancer: A systematic review and meta-analysis
A meta-analysis of 17 studies confirmed that high ultra-processed food consumption is associated with a 65% higher odds of obesity.
Consumption of Ultra-Processed Foods Increases the Likelihood of Having Obesity in Korean Women
Among Korean women, those with the highest ultra-processed food intake had 51% higher odds of obesity and 64% higher odds of abdominal obesity; no significant association was found in men.
Ultra-processed foods and cancer risk: from global food systems to individual exposures and mechanisms
A review highlights that ultra-processed foods may increase cancer risk through obesogenic properties and exposure to potentially carcinogenic compounds like food additives.
A Close Relationship Between Ultra-Processed Foods and Adiposity in Adults in Southern Italy
In a study of 175 adults in southern Italy, ultra-processed food consumption increased with BMI, and soft drinks were the most common ultra-processed food consumed.
Ultra-processed Food and Obesity: What Is the Evidence?
A 2024 review concludes that greater ultra-processed food consumption has been a key driver of obesity, supported by high-quality clinical data, and that the concept captures effects not explained by existing nutrient-based frameworks.
The role of ultra-processed food in obesity
A 2025 review summarizes that dietary patterns high in ultra-processed foods promote overeating and increase obesity risk through effects on satiety, food reward, and gut microbiota, among other mechanisms.