“As people consume more junk foods 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 disease,” said the lead author, Amanda Grech, PhD, a postdoctoral research fellow at the Charles Perkins Centre in Sydney, in a press release.
More Than Half Our Daily Calories Come From Highly Processed Foods
Unprocessed or minimally processed foods are found along the perimeter of the grocery store — fresh fruits and vegetables, raw meats, and dairy products. On the flip side, highly processed foods like cookies, crackers, chips, and frozen pizza typically contain high levels of added sugar, fat, and salt, and not much in the way of vitamins and fiber. Evidence suggests that Americans are consuming more processed foods and less minimally processed ones. An 18-year study published in the American Journal of Clinical Nutrition in October 2021 found that ultra-processed food consumption grew from 53.5 percent of calories in 2001–2002 to 57 percent by the study’s end, in 2017–2018.
Protein Leverage Hypothesis: People Eat More Fats and Carbs to Satisfy Protein Demand
Researchers continue to build a case for what they call the protein leverage hypothesis, a concept first put forward in 2005 by the University of Sydney faculty members and coauthors of this study, David Raubenheimer, DPhil, and Stephen Simpson, PhD. According to the hypothesis, people overeat fats and carbohydrates because of the body’s strong appetite for protein, which the body actively favors over everything else. Because so much of modern diets consists of highly processed and refined foods — which are low in protein — people are driven to consume more energy-dense (meaning calorie-dense) foods until they satisfy their protein demand. Why is protein so important? Proteins are the building blocks of life, the authors wrote. Every cell in the body contains them, and they are used to repair cells or make new ones — it’s estimated that over a million forms of protein are needed to allow a human body to function.
People Who Ate Less Protein at Breakfast Consumed More Calories Throughout the Day
Investigators used data from a 2011–2012 cross-sectional survey of nutrition and physical activity in 9,341 adults (average age 46 years old), known as the National Nutrition and Physical Activity Survey. They found the participants’ average energy intake was 8,671 kilojoules, or 2,072 calories, with the average percentage of energy from protein being just 18.4 percent, compared with 43.5 percent from carbohydrates and 30.9 percent from fat, 2.2 percent from fiber, and 4.3 percent from alcohol. Kilojoules is the way potential energy or calories are measured in Australia. Calorie needs for adult women range from 1,600 to 2,200 per day, and for men 2,000 to 3,000 calories per day, according to the American Academy of Nutrition and Dietetics. Researchers then plotted calorie intake versus the time of consumption and found that the pattern matched that predicted by the Protein Leverage Hypothesis; participants who ate lower amounts of protein in their first meal of the day went on to increase their overall food intake in subsequent meals, whereas those who received the recommended amount of protein did not — they actually ate less food throughout the rest of the day. They also found a statistically significant difference between groups by the third meal of the day. People with a higher proportion of energy from protein at the start of the day had much lower total calorie intake for the day, whereas those who consumed foods low in protein at the start of the day proceeded to increase consumption of calories, indicating they were seeking to compensate for the lack of protein by eating and drinking more. The trend was observed even though the first meal was the smallest for both groups, with the least amount of energy and food consumed, whereas the last meal was the largest.
People Who Ate Less Protein in Their First Meal Snacked More Throughout the Day
Participants with a lower proportion of protein than recommended at the first meal consumed more snacks in the form of calorie-dense foods high in saturated fats, sugars, salt, or alcohol throughout the day, and less of the recommended five food groups (grains, vegetables and legumes, fruit, dairy, and meats) at mealtime. “It’s increasingly clear that our bodies eat to satisfy a protein target,” said Dr. Raubenheimer in the press release. The problem is that the amount of protein in Western diets is decreasing, he says. “So, you have to consume more food to reach your protein target, which effectively elevates your daily energy intake.” Because humans have a stronger appetite for protein than for the main energy-providing nutrients of fats and carbohydrates, if the protein in our diet is diluted with fats and carbohydrates, we will eat more energy to get the protein that our bodies crave, says Raubenheimer. The findings support the central role of protein in the obesity epidemic, he says. “Obesity, diabetes, cardiovascular disease — they’re all driven by diet, and we have to use what we’re learning to bring them under control,” said Raubenheimer.
Diets Higher in Protein May Leave People Feeling Less Hungry
“I find the concept of ‘protein hunger’ to be an interesting one, but I do think that we need to tailor this to fit the individual,” says Fatima Cody Stanford, MD, MPH, an associate professor of medicine and pediatrics at Harvard Medical School and an obesity medicine physician-scientist at Massachusetts General Hospital Weight Center in Boston. Dr. Stanford was not part of this research. There’s no “one-size-fits-all” when it comes to protein requirements — it can vary between 10 and 35 percent of the total amount of calories consumed, says Dr. Stanford. “However, we do know that higher-protein diets, on average, do lead to better satiety, which then leads to less consumption,” she says.
A Higher Protein Diet Doesn’t Necessarily Mean You Have to Eat More Meat
Stanford points out that the concept of a higher protein diet is the basis for several popular diets, including Atkins and the ketogenic diet. But because not everyone responds the same way to dietary interventions, macronutrient recommendations (such as protein, fats, and carbs) need to be tailored to the individual as part of an overall strategy to achieve or maintain a healthy weight, she says. “Also, it’s important to note that a higher protein diet doesn’t necessarily mean higher animal protein in the diet. Protein comes from variety of sources, including animals, whole grains, legumes, and vegetables,” says Stanford.
