Study Confirms Processed Foods Key to Rising Obesity
“Protein hunger” drives overeating, according to a large-scale population study.
Mounting evidence that highly processed and refined foods are the biggest contributor to rising obesity rates in the Western world is supported by a year-long study of the eating habits of 9,341 Australians.
The new study 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. 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 proposed in 2005 by Professors Raubenheimer and Stephen Simpson, the protein leverage hypothesis holds that people eat too many fats and carbohydrates due to the body’s high appetite for protein, which the body actively prioritizes over everything else. Because so much of modern diets consist of highly processed and refined foods – which are low in protein – people are driven to consume more energy-dense foods until they meet their protein demand. .
Processed foods lack protein and cause cravings
“As people consume more junk food or highly processed and refined foods, they dilute their dietary protein and increase their risk of overweight and obesity, which we know increases the risk of chronic disease,” a said lead author, postdoctoral fellow Dr. Amanda Grech. Researcher at the CPC and at the University’s School of Life and Environmental Sciences.
“It is increasingly clear that our body eats to satisfy a protein target,” added Professor David Raubenheimer, Leonard Ullmann Chair in Nutritional Ecology at the School of Life and Environmental Sciences. “But the problem is that the foods in Western diets contain less and less protein. So you need to eat more of it to reach your protein goal, which effectively increases your daily energy intake.
“Humans, like many other species, have a stronger appetite for protein than for the main energy nutrients of fat and carbohydrate. This means that if the protein in our diet is diluted with fat and carbohydrate, we will eat more energy to get the protein our body needs.
Proteins essential for good health
Proteins are the building blocks of life: every cell in the body contains 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 required for the human body to function. Sources of protein 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 nutrition and physical activity survey of 9,341 adults, known as the National Nutrition and Physical Activity Survey, which was conducted from May 2011 to June 2012, with an average age 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 from protein being only 18.4%, compared to 43.5% from carbohydrates and 30 9% for lipids, and only 2.2% for fibers and 4.3% for proteins. alcohol.
They then plotted energy intake against time of consumption and found that the pattern matched that predicted by the protein leverage hypothesis. Those who ate low amounts of protein at their first meal of the day continued to increase their overall food intake at subsequent meals, while those who received the recommended amount of protein did not – and, in fact, decreased their food intake throughout the day. .
“Protein Hunger” Leads to Overeating
They also found a statistically significant difference between the groups at the third meal of the day: those who had a higher proportion of energy from protein at the start of the day had a much lower total energy intake for the day. Meanwhile, those who ate low-protein foods early in the day increased their intake, indicating that they were seeking to compensate with higher overall energy consumption. This is despite the fact that the first meal was the smallest for both groups, with the least energy and food consumed, while the last meal was the largest.
Participants with a lower than recommended proportion of protein at the first meal ate more discretionary foods — energy-dense foods high in saturated fat, sugars, salt, or alcohol — throughout the day, and less than the five recommended food groups (cereals, vegetables). /legumes; fruit; dairy products and meats). As a result, they had an overall poorer diet at each meal, their percentage of protein energy decreasing even as their discretionary food intake increased – an effect scientists call “protein dilution”.
Effect observed in other studies
Professor Raubenheimer and his colleagues have already observed this effect in other studies for more than a decade, including randomized controlled trials.
“The problem with randomized controlled trials is that they treat diet like a disease, when it’s not,” Dr. Grech said. “Lab studies may not be indicative of what people actually eat and do at the population level. This study is therefore important because it builds on work showing that people are looking for protein. And this confirms that at the population level, as the proportion of energy from protein increases in the diet, people eat less fat and carbohydrates.
While many factors contribute to excess weight gain – including eating habits, physical activity levels and sleep routines – scientists at the University of Sydney say the body’s high demand for protein and its lack of highly processed and refined foods are a key driver of energy. overconsumption and obesity in the western world.
Explanation of obesity
“The results support an integrated ecological and mechanistic explanation of obesity, in which low-protein and highly processed foods lead to higher energy intake in response to a nutritional imbalance driven by a dominant appetite for protein,” said said Professor Raubenheimer. “It supports a central role for protein in the obesity epidemic, with important implications for global health.”
Seeking to understand how protein drives human nutrition has also sought to lead Professor Raubenheimer to study the diets of people in some of the most remote places, from the Congo to the Himalayas. “The protein mechanism of appetite is a revolutionary idea,” he said. “Obesity, diabetes, cardiovascular disease – they’re all food-driven, and we need to use what we learn to get them under control.”
The CPC team study was chosen by the editors of Obesity as one of the top five papers of the year, with study leader Prof. Raubenheimer invited to speak at the Journal’s Annual Obesity Symposium in San Diego on Nov. 4.
Reference: “Macronutrient (im)balance drives energy intake in an obesogenic dietary environment: An ecological analysis” by Amanda Grech, Zhixian Sui, Anna Rangan, Stephen J. Simpson, Sean CP Coogan, and David Raubenheimer, November 2 2022, Obesity.
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