Forget Salt, Sugar And Oil: Are Ultra-Processed Foods To Blame For Obesity?

While nutritional science has pointed to overconsumption of fats and carbohydrates as the cause for obesity, new research now finds that “ultra-processed foods” or UPFs – instant, long shelf-life convenient foods that have undergone significant processing – is the bigger culprit. After decades of research finding an association between UTPs and obesity, the latest research is the first small-scale randomised, controlled research to establish a causal link.

In a recent study conducted by the National Institutes of Health (NIH) published in Cell Metabolism, researchers Kevin Hall and his colleagues found that ultra-processed foods or UPFs can distort signals between the gut and the brain that is responsible for telling us that we feel full, therefore leading to over-eating. The study’s findings point to the dramatic increase of UPFs consumption in modern diets as the main culprit for the global obesity crisis. 

UPFs are foods that have been altered to the point where it is difficult to discern the underlying ingredients, which are typically a number of already-refined and reconstituted products such as cheap vegetable oils, flours, protein isolates, sugars and other additives such as emulsifiers and flavourings. While some common UPFs have been on supermarket shelves for decades, such as sliced bread or commercially produced baked goods, UPFs have never taken up more space in history than in today’s modern diet. As scary as it sounds, UPFs now account for more than half of all the calories eaten in a number of advanced economies, including the United States and United Kingdom. 

Some UPFs are obvious, such as the conventional fare of fast food meals, chicken nuggets and the like. Other types may even be marketed as “healthier” alternatives, such as “lighter” margarines and vitamin-fortified breakfast cereals. 

Over the past years, a number of large-scale studies have investigated the link between high consumption of UPFs and rates of obesity and other chronic health problems. A 2018 French study that involved more than 100,000 adults, for instance, found a 10% increase of UPFs in one’s diet could lead to a higher overall risk of cancer. 

The shifted focus on the health impact of UPFs originated from research in the 1980s by Carlos Monteiro. He found that despite the fact that people were buying less sugar and oil, the overall sugar consumption kept increasing due to the ready-to-eat packaged products and ultra-processed items that had become ubiquitous on supermarket shelves and begun to replace freshly cooked meals. It was out of this research that the “Nova system” was created, which categorised foods into 4 different kinds: unprocessed and minimally processed, processed culinary ingredients, processed foods, and UPFs. 

But Hall’s 2019 study is the first of its kind to establish a causal link. In randomised controlled conditions – the methodology used in clinical trials – the study tested whether diets high in UPFs could actually cause overeating and weight gain in 10 men and 10 women over 4 weeks. For half of the duration of the study, the participants ate mostly ultra-processed meals, while in the other half, they ate mostly unprocessed foods. Both diets were matched in terms of calories, sugar, protein, fibre and fat – but crucially, participants ate an extra 500 calories a day on the UPF diet. Blood tests showed that the UPF diet kept elevated the hormones in the body responsible for signalling hunger, which kept participants unsatiated and therefore had to eat more. 

Hall says that his study makes clear that the food system needs a dramatic reconstruction, or more accurately, a return back to fresh meals made at home. While the multinational food industry has a vested interest in reformulating products with labels touting its health benefits and will continue to fund non-peer-reviewed research to try and dismantle the scientific evidence, the best way is to steer clear of foods that you won’t be able to recreate at home. 

But above the individual action level, there are policy considerations emerging from his study. For developing countries, the prevalence of cheap and available UFPs combined with aggressive marketing from corporations will make it increasingly difficult for the majority of the population to thrive on a wholesome diet, paving the road to more public health crises. In advanced economies, to avoid UPFs would require rejecting the vast majority of what is on offer at grocery stores. 

According to the World Obesity Federation’s global Childhood Obesity Atlas, only 1 in 10 countries have a mere 50% chance of achieving the WHO target of keeping obesity rates down by 2025. Asian countries are the most vulnerable to the risk as it experiences rapid economic development and urbanisation, accompanied by trends towards convenient foods. The Atlas predicts that China is looking at almost 62 million obese children by 2030, while India will see the population grow to 27 million. 

The recent WHO-Unicef-Lancet commission has warned that predatory corporate marketing and commercial practices must be tackled. If global health is a priority, then governments must step up structural efforts and hold businesses to account to help reduce UPFs from the modern diet.

Lead image courtesy of Getty Images.