Scientists Find That “Protein Hunger” Drives Overeating, Obesity

A study confirms that processed foods are the key to the rise in obesity

‘Protein hunger’ drives overeating, large-scale population study shows.

growing evidence that highly processed and refined foods are the main contributor a rising obesity rates in the western world is supported by a year-long study of the dietary habits of 9,341 Australians.

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

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 everything 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 a craving

“As people consume more junk food or highly processed and refined foods, dilute their dietary protein and increase their risk of becoming overweight and obese, which we know increases the risk of chronic disease,” said lead author Dr. Dr. Amanda Grech, postdoctoral student. Research Fellow of the CPC and the University’s Faculty of Life and Environmental Sciences.

“It is becoming increasingly clear that our bodies eat to satisfy a protein goal,” added Professor David Raubenheimer, holder of the Leonard Ullmann Chair in Nutritional Ecology in the School of Life and Environmental Sciences. “But the problem is that 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 fat 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 a 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 like 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 mean 46.3 years. They found that the population’s average energy intake 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% from protein. % of the fats, and only 2.2% of the fibers and 4.3% of the fats. alcohol.

They then plotted energy intake versus 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, and in fact reduced their food intake over time. day length. .

‘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 start 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 a higher total energy intake. This is despite the fact that the first meal was 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 protein ratio at their first meal ate more discretionary foods (energy-dense foods high in saturated fat, sugar, salt, or alcohol) throughout the day, and fewer of all five groups of recommended foods (grains, vegetables). /legumes; fruits; dairy and meat). Consequently, they had a poorer diet overall at each meal, and their percentage of protein energy decreased even as their discretionary food intake increased, an effect scientists call ‘protein dilution’.

Effect seen in other studies

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

“The problem with randomized controlled trials is that they treat diet like a disease, when it isn’t,” 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 work and shows that people seek protein. And it confirms that, at a population level, as the proportion of energy from protein in the diet increases, people consume less fat and carbohydrates.”

While many factors contribute to excess 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.

Explanation of obesity

“The results support an integrated ecological and mechanistic explanation for 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 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 need to use what we are learning to control them.”

The CPC team study was chosen by the editors of Obesity as one of the top five articles of the year, with study leader Professor Raubenheimer invited to speak at the annual Obesity Journal Symposium in San Diego on November 4.

Reference: “Macronutrient (Im)balance Drives Energy Intake in an Obesogenic Food Environment: An Ecological Analysis” by Amanda Grech, Zhixian Sui, Anna Rangan, Stephen J. Simpson, Sean CP Coogan, and David Raubenheimer, Nov 2 from 2022, Obesity.
DOI: 10.1002/oby.23578