Columna de Camila Corvalán – Publiacada originalmente en World Obesity Federation.

How do you define what makes food healthy or unhealthy?

Traditionally, the quality of foods was based on their nutrient (carbohydrates, proteins, fats, minerals) and calories content. Interestingly, this is why package foods include a nutrient fact panel. However, mounting evidences suggests that the degree of processing of the food – defined as “any action that alters food from its natural state” – isn’t something necessarily measurable in nutrition labels but could ultimately be a better marker of food healthiness.

Today, we are surrounded by UPFs: soft drinks, packaged snacks, cookies and biscuits, candies, ready to -eat or ready-to-heat meals, instant noodles, all of which are constantly on display and easily accessible to all.

Until the middle of the 20th century, UPF were almost non-existent. However thereafter, the nutrition transition has made their relevance for the food supply chain paramount, including in low-middle income countries. In Mexico and Chile, almost a third of the total calories consumed by the population is derived from UPF. In other parts of the world like the UK and the USA, this rises to almost 60%. Shockingly, the highest UPF consumption is observed in children and adolescents: in several countries, UPF contributes to more than 50% of the daily total calories consumed by children.

The rise in the global prevalence of obesity has occurred in parallel with the increase in UPF consumption worldwide. Several studies have confirmed that increased consumption of UPF is associated with weight gain. In fact, evidence suggests that people consuming high amounts of UPF can have up to a 50% higher risk of developing obesity compared to those consuming less UPF. In 2019, researchers at the National Institutes of Health published results from a clinical trial in which 20 healthy adults lived in a controlled environment for four weeks receiving either unprocessed (whole foods) or processed food diets.  The results couldn’t be more clear-cut: participants ate significantly more when the food was processed, accompanied by a significant weight gain despite the limited amount of time of the intervention. Recently, Dr Chris Van Tulleken conducted a similar experiment for a BBC documentary: after eating 80% of daily calories from UPF for a period of 4 weeks, he reported a weight gain of 6.5 kg.

The association between UPF consumption and weight gain can be explained by at least three mechanisms.

First, UPFs are rich in calories, sugars, unhealthy saturated and trans fats and sodium, contributing to the rise in diet-related non-communicable diseases. Unfortunately, trends suggest that today, for many, the consumption of UPFs has replaced the consumption of natural or less processed foods that would generally be sources of proteins, vitamins, minerals, and fiber. Second, it is very difficult to stop eating UPF. UPFs do not have to be cut or chewed as much as whole foods , thus  they  travel  rapidly into our stomachs without activating our satiety signals.

In a  trial conducted at the National Institutes of Health of USA, participants in the UPF diet group ate faster and had higher levels of a hormone that fuels hunger and lower levels of a hormone that signals fullness.  In the BBC experiment, Dr Van Tulleken noticed the following: “But worst of all, my brain rewired itself just as if I had developed an addiction to a drug of abuse”. A brain MRI scan confirmed Dr Van Tulleken’s theory: connections between the reward centre and areas that drive repetitive automatic behaviour significantly increased after following a 1-month UPF diet. He added: “my brain was telling me to eat ultra-processed food without my even wanting it”.

Third, UPFs are hyper-palatable, pleasing all senses, and extremely convenient to eat. For children who have less self-control and autonomy, it makes it almost impossible to escape the overwhelming temptation of UPF overconsumption, a factor exacerbated by aggressive marketing campaigns.

If we want to address the current obesity pandemic, there is a need to dramatically decrease the consumption of UPF. Several non-profit organisations and UN agencies have made pleas to reduce the availability and consumption of UPFs, particularly for children. As we now know, the creation of healthier environments will only be achievable through the implementation of a package of policies that complement each other, and our approach towards UPF should be no different.