On the opposite side of the spectrum from malnutrition, obesity stands out as one of the most glaring and yet often overlooked public health challenges of our time. Strangely juxtaposed with undernutrition, the worldwide prevalence of overweight and obesity, often referred to as “globesity,” is on the rise world over.
In the mid-1990s, Carlos Monteiro, a nutritional epidemiologist in Brazil, noticed this alarming trend in his country. Along with researchers at the University of São Paulo, he investigated changes in food purchasing habits among Brazilian households. They observed a decline in the consumption of traditional staples like sugar, salt, cooking oils, rice, and beans, while noting an increase in the consumption of processed foods such as sodas, sausages, instant noodles, packaged breads, and cookies.
To classify this category of food, they introduced the term “ultraprocessed foods” (UPFs) and outlined its definition. Subsequent studies linked UPFs to weight gain in both children and adults in Brazil. Furthermore, research has shown associations between UPFs and various health conditions, including heart disease, Type 2 diabetes, obesity, gastrointestinal diseases, depression, and increased mortality rates.
As ultraprocessed foods became a significant component of diets globally, worldwide adult obesity more than doubled since 1990, and adolescent obesity has quadrupled.
What are Ultraprocessed foods?
To analyse foods based on their processing methods, Dr. Monteiro and colleagues devised the Nova food classification system. Widely adopted globally, this system categorises foods into four groups:
1. Unprocessed or minimally processed foods, including fresh or frozen fruits and vegetables, beans, meat, poultry, fish, eggs, milk, yogurt, rice, pasta, and basic cooking ingredients like herbs and spices.
2. Processed culinary ingredients like cooking oils, butter, sugar, honey, vinegar, and salt.
3. Processed foods created by combining ingredients from Category 1 with those from Category 2, often preserved or modified using simple methods such as canning, fermentation, or baking. Examples include freshly baked bread, cheeses, and canned vegetables or fish, sometimes containing preservatives for extended shelf life.
4. Ultraprocessed foods produced through industrial methods, containing uncommon ingredients like high-fructose corn syrup, hydrogenated oils, and concentrated proteins such as soy isolate. These foods are often laden with additives like flavorings, colorings, or emulsifiers to enhance appearance and taste. Examples include sodas, energy drinks, chips, candies, flavored yogurts, margarine, chicken nuggets, and packaged breads, among others.
Do UPFs cause harm?
Research linking ultraprocessed foods (UPFs) to adverse health outcomes primarily relies on observational studies, tracking participants’ diets and health over extended periods. A comprehensive review published in 2024 found that UPF consumption was associated with 32 health issues, including heart disease-related deaths, Type 2 diabetes, and common mental health conditions like anxiety and depression.
While these studies offer valuable insights due to their large sample sizes, which can span millions of individuals over many years, they also have limitations. Lauren O’Connor, a nutrition scientist, suggests caution in categorising vastly different foods like Twinkies and breakfast cereals under a single label. Certain UPFs, such as sodas and processed meats, are more evidently harmful, while others like flavored yogurts and whole grain breads may confer health benefits.
Clinical trials are necessary to establish causality, with one small study indicating that participants consumed more calories and gained weight on a UPF diet compared to an unprocessed diet. However, further research is needed to confirm these findings and elucidate the mechanisms linking UPFs to obesity and metabolic conditions.
What damage can a UPF diet do?
Despite numerous strong opinions on the detrimental effects of ultraprocessed foods (UPFs), there is a scarcity of rigorous scientific research to back it up. UPFs are often preferred for their affordability, convenience, and accessibility, potentially displacing healthier options in our diets. However, scientists hypothesise that UPFs may have direct impacts on health.
These foods are easy to overconsume due to their palatability, high caloric density, and texture. Additionally, they may lead to blood sugar spikes, arterial damage, inflammation, hormone disruption, or gut microbiome disturbances. Clinical trials are underway to investigate these theories, aiming to identify the most harmful UPFs and explore methods for enhancing their nutritional quality.
Nevertheless, most experts believe that multiple factors contribute to the adverse health effects associated with UPFs, emphasising the complex nature of the relationship between diet and health.
What is the future of UPFs?
Dr. Monteiro advocates for a cautious approach by completely avoiding UPFs. He recommends making substitutions such as switching from flavored yogurt to plain yogurt with fresh fruit or opting for freshly baked bread from local bakeries instead of packaged bread, where feasible.
Others propose a more balanced strategy, advising individuals to limit consumption of UPFs lacking essential nutrients, such as soda and cookies, while increasing intake of fruits, vegetables, whole grains (whether ultraprocessed or not), legumes, nuts, and seeds. Till we know more, sticking to home-cooked meals as much as you can, and using minimally processed foods, is a good way to balance your diet.
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