Ultra-Processed Foods Drive Obesity Increase

A year-long study of the eating habits of 9,341 Australians has supported growing evidence that highly processed and refined foods are the main contributors to rising obesity rates in the Western world.

The new study, which appears in the latest issue of the journal Obesity , conducted by the Charles Perkins Center (CPC) at the University of Sydney, was based on a national nutrition and physical activity survey conducted by the Australian Bureau of Statistics (ABS). ), and further supports the ’Protein Leverage Hypothesis’.

First introduced in 2005 by Professors Raubenheimer and Stephen Simpson, the protein leverage hypothesis argues that people overeat fats and carbohydrates due to the body’s strong appetite for protein, which the body actively favors over all else. Because much of modern diets consist of highly processed and refined foods, which are low in protein, people are forced to consume more energy-dense foods until their protein demand is met.

Processed foods lack protein and create cravings

"As people consume more junk food or highly processed and refined foods , they dilute their dietary protein and increase their risk of being overweight and obese, which we know increases the risk of chronic diseases," said lead author Dr. Dr. Amanda Grech, postdoctoral researcher. Fellow of the CPC and the Faculty of Life and Environmental Sciences of the university.

“It is increasingly clear that our bodies eat to satisfy a protein target,” added Professor David Raubenheimer, Leonard Ullmann Chair of Nutritional Ecology in the School of Environmental and Life Sciences. “But the problem is that the foods in Western diets have less and less protein. Therefore, you must consume more to reach your protein goal, which effectively raises your daily energy intake.

“Humans, like many other species, have a greater appetite for protein than for the main energy-providing nutrients, fats and carbohydrates. That means that if the protein in our diet is diluted with fats and carbohydrates, we will eat more energy to get the protein our bodies crave.”

Essential protein for good health

Proteins are the building blocks of life: all cells in the body contain them and they are used to repair cells or create new ones; and it is estimated that more than one million forms of protein are needed to allow a human body to function. Protein sources include meats, milk, fish, eggs, soy, legumes, beans, and some grains such as wheat germ and quinoa.

Scientists at the University of Sydney analyzed data from a cross-sectional survey of nutrition and physical activity in 9,341 adults, known as the National Nutrition and Physical Activity Survey, which was carried out between May 2011 and June 2012, with an age average of 46.3 years. They found that the average energy intake of the population was 8,671 kilojoules (kJ), with the average percentage of energy coming from protein being only 18.4%, compared to 43.5% from carbohydrates and 30.9%. % of fat, and only 2.2% of fiber and 4.3% of fat.

They then plotted energy intake against consumption time and found that the pattern matched that predicted by the protein leverage hypothesis. Those who consumed lower amounts of protein at their first meal of the day increased their total food intake at subsequent meals, while those who received the recommended amount of protein did not do so and, in fact, reduced their food intake throughout. throughout the day.

’Protein hunger’ found to lead to overeating

They also found a statistically significant difference between the groups at the third meal of the day: those with a higher proportion of energy from protein at the beginning of the day had a much lower total energy intake for the day. For their part, those who consumed low-protein foods at the beginning of the day proceeded to increase consumption, indicating that they sought to compensate with greater total energy consumption. This is despite the first meal being the smallest for both groups, with the least amount of energy and food consumed, while the last meal was the largest.

Participants with a lower than recommended proportion of protein at the first meal consumed more discretionary foods (energy-dense foods high in saturated fat, sugars, salt, or alcohol) throughout the day, and fewer of the five groups of recommended foods (grains, vegetables)/legumes; fruit; dairy and meat). Consequently, they had an overall poorer diet at each meal, and their percentage of protein energy decreased even as their discretionary food intake increased, an effect scientists call "protein dilution."

Effect observed in other studies

Professor Raubenheimer and his colleagues have seen this effect before in other studies for more than a decade, including randomized controlled trials.

“The problem with randomized controlled trials is that they treat diet as a disease, when it is not,” Dr. Grech said. “Laboratory studies may not be indicative of what people actually eat and do at a population level. Therefore, this study is important as it builds on the work and shows that people seek protein. “And it confirms that, at the population level, as the proportion of energy from protein in the diet increases, people consume less fat and carbohydrates.”

While many factors contribute to excessive weight gain, including eating patterns, physical activity levels and sleep routines, scientists at the University of Sydney argue that the body’s powerful demand for protein and its lack of highly processed and refined is a key driver of energy. overconsumption and obesity in the Western world.

Obesity explained

“The results support an integrated ecological and mechanistic explanation of obesity, in which highly processed, low-protein foods lead to increased energy intake in response to a nutrient imbalance driven by a dominant appetite for protein.” said Professor Raubenheimer. "It supports a central role for the protein in the obesity epidemic, with significant implications for global health."

Seeking to understand how protein drives human nutrition has also led Professor Raubenheimer to study the diets of people in some of the most remote places, from the Congo to the Himalayas. “The mechanism of protein in appetite is a revolutionary idea,” he said. “Obesity, diabetes, cardiovascular disease – they are all driven by diet and we have to use what we are learning to control them.”

Importance of the study

What is already known?

There is fundamental disagreement about the drivers and mechanisms underlying the obesity epidemic. The protein leverage hypothesis (PLH) proposes that in macronutritionally imbalanced food environments, strong human regulation of protein intake drives excessive energy consumption and obesity ("protein leverage") in diets. diluted in proteins and highly processed. Protein leverage is supported by several randomized controlled trials, and here we tested PLH in realistic ecological settings.

What does this study add?

Energy intake is a negative function of dietary protein concentration, and the food category primarily associated with dilution of dietary protein is highly processed discretionary foods.

How might these results change the direction of research or the focus of clinical practice?

Energy overconsumption driven by a strong human protein appetite interacting with imbalanced food environments highlights the importance of interventions focused on food environments. Methodologically, our analysis addresses the controversy over dietary recall data by showing that a phenomenon established in randomized controlled trials (protein leverage) is also detectable in dietary surveillance data, thus establishing both causality (non-experimental settings) such as the relevance (in population settings) of protein leverage.