Nutrition researcher Kevin Hall strives to project a Zen-like state of equanimity. In his often contentious field, he says he is more bemused than frustrated by the tendency of other scientists to “cling to pet theories despite overwhelming evidence that they are mistaken.” Some of these experts, he tells me with a sly smile, “have a fascinating ability to rationalize away studies that don’t support their views.”
Among those views is the idea that particular nutrients such as fats, carbs or sugars are to blame for our alarming obesity pandemic. (Globally the prevalence of obesity nearly tripled between 1975 and 2016, according to the World Health Organization. The rise accompanies related health threats that include heart disease and diabetes.) But Hall, who works at the National Institute of Diabetes and Digestive and Kidney Diseases, where he runs the Integrative Physiology section, has run experiments that point fingers at a different culprit. His studies suggest that a dramatic shift in how we make the food we eat—pulling ingredients apart and then reconstituting them into things like frosted snack cakes and ready-to-eat meals from the supermarket freezer—bears the brunt of the blame. This “ultraprocessed” food, he and a growing number of other scientists think, disrupts gut-brain signals that normally tell us that we have had enough, and this failed signaling leads to overeating.
Hall has done two small but rigorous studies that contradict common wisdom that faults carbohydrates or fats by themselves. In both experiments, he kept participants in a hospital for several weeks, scrupulously controlling what they ate. His idea was to avoid the biases of typical diet studies that rely on people’s self-reports, which rarely match what they truly eat. The investigator, who has a physics doctorate, has that discipline’s penchant for precise measurements. His first study found that, contrary to many predictions, a diet that reduced carb consumption actually seemed to slow the rate of body fat loss. The second study, published this year, identified a new reason for weight gain. It found that people ate hundreds more calories of ultraprocessed than unprocessed foods when they were encouraged to eat as much or as little of each type as they desired. Participants chowing down on the ultraprocessed foods gained two pounds in just two weeks.
“Hall’s study is seminal—really as good a clinical trial as you can get,” says Barry M. Popkin, a professor of nutrition at the University of North Carolina at Chapel Hill, who focuses on diet and obesity. “His was the first to prove that ultraprocessed foods are not only highly seductive but that people tend to eat more of them.” The work has been well received, although it is possible that the carefully controlled experiment does not apply to the messy way people mix food types in the real world.
The man who designed the research says he is not on a messianic mission to improve America’s eating habits. Hall admits that his four-year-old son’s penchant for chicken nuggets and pizza remains unshakable and that his own diet could and probably should be improved. Still, he believes his study offers potent evidence that it is not any particular nutrient type but the way in which food is manipulated by manufacturers that plays the largest role in the world’s growing girth. He insists he has no dog in any diet wars fight but is simply following the evidence. “Once you’ve stepped into one camp and surrounded yourself by the selective biases of that camp, it becomes difficult to step out,” he says. Because his laboratory and research are paid for by the national institute whatever he finds, Hall notes that “I have the freedom to change my mind. Basically, I have the privilege to be persuaded by data.” (...)
Processed Calories
Hall likes to compare humans to automobiles, pointing out that both can operate on any number of energy sources. In the case of cars, it might be diesel, high-octane gasoline or electricity, depending on the make and model. Similarly, humans can and do thrive on any number of diets, depending on cultural norms and what is readily available. For example, a traditional high-fat/low-carb diet works well for the Inuit people of the Arctic, whereas a traditional low-fat/high-carb diet works well for the Japanese. But while humans have evolved to adapt to a wide variety of natural food environments, in recent decades the food supply has changed in ways to which our genes—and our brains—have had very little time to adapt. And it should come as no surprise that each of us reacts differently to that challenge.
At the end of the 19th century, most Americans lived in rural areas, and nearly half made their living on farms, where fresh or only lightly processed food was the norm. Today most Americans live in cities and buy rather than grow their food, increasingly in ready-to-eat form. An estimated 58 percent of the calories we consume and nearly 90 percent of all added sugars come from industrial food formulations made up mostly or entirely of ingredients—whether nutrients, fiber or chemical additives—that are not found in a similar form and combination in nature. These are the ultraprocessed foods, and they range from junk food such as chips, sugary breakfast cereals, candy, soda and mass-manufactured pastries to what might seem like benign or even healthful products such as commercial breads, processed meats, flavored yogurts and energy bars.
Ultraprocessed foods, which tend to be quite high in sugar, fat and salt, have contributed to an increase of more than 600 available calories per day for every American since 1970. Still, although the rise of these foods correlates with rising body weights, this correlation does not necessarily imply causation. There are plenty of delicious less processed foods—cheese, fatty meats, vegetable oil, cream—that could play an equal or even larger role. So Hall wanted to know whether it was something about ultraprocessing that led to weight gain. “Basically, we wondered whether people eat more calories when those calories come from ultraprocessed sources,” he says. (...)
A Gut-Brain Disconnect
Why are more of us tempted to overindulge in egg substitutes and turkey bacon than in real eggs and hash brown potatoes fried in real butter? Dana Small, a neuroscientist and professor of psychiatry at Yale University, believes she has found some clues. Small studies the impact of the modern food environment on brain circuitry. Nerve cells in the gut send signals to our brains via a large conduit called the vagus nerve, she says. Those signals include information about the amount of energy (calories) coming into the stomach and intestines. If information is scrambled, the mixed signal can result in overeating. If “the brain does not get the proper metabolic signal from the gut,” Small says, “the brain doesn’t really know that the food is even there.”
Neuroimaging studies of the human brain, done by Small and others, indicate that sensory cues—smells and colors and texture—that accompany foods with high-calorie density activate the striatum, a part of the brain involved in decision-making. Those decisions include choices about food consumption.
And that is where ultraprocessed foods become a problem, Small says. The energy used by the body after consuming these foods does not match the perceived energy ingested. As a result, the brain gets confused in a manner that encourages overeating. For example, natural sweeteners—such as honey, maple syrup and table sugar—provide a certain number of calories, and the anticipation of sweet taste prompted by these foods signals the body to expect and prepare for that calorie load. But artificial sweeteners such as saccharin offer the anticipation and experience of sweet taste without the energy boost. The brain, which had anticipated the calories and now senses something is missing, encourages us to keep eating.
To further complicate matters, ultraprocessed foods often contain a combination of nutritive and nonnutritive sweeteners that, Small says, produces surprising metabolic effects that result in a particularly potent reinforcement effect. That is, eating them causes us to want more of these foods. “What is clear is that the energetic value of food and beverages that contain both nutritive and nonnutritive sweeteners is not being accurately communicated to the brain,” Small notes. “What is also clear is that Hall has found evidence that people eat more when they are given highly processed foods. My take on this is that when we eat ultraprocessed foods we are not getting the metabolic signal we would get from less processed foods and that the brain simply doesn’t register the total calorie load and therefore keeps demanding more.”
by Ellen Ruppel Shell, Scientific American | Read more:
Among those views is the idea that particular nutrients such as fats, carbs or sugars are to blame for our alarming obesity pandemic. (Globally the prevalence of obesity nearly tripled between 1975 and 2016, according to the World Health Organization. The rise accompanies related health threats that include heart disease and diabetes.) But Hall, who works at the National Institute of Diabetes and Digestive and Kidney Diseases, where he runs the Integrative Physiology section, has run experiments that point fingers at a different culprit. His studies suggest that a dramatic shift in how we make the food we eat—pulling ingredients apart and then reconstituting them into things like frosted snack cakes and ready-to-eat meals from the supermarket freezer—bears the brunt of the blame. This “ultraprocessed” food, he and a growing number of other scientists think, disrupts gut-brain signals that normally tell us that we have had enough, and this failed signaling leads to overeating.
Hall has done two small but rigorous studies that contradict common wisdom that faults carbohydrates or fats by themselves. In both experiments, he kept participants in a hospital for several weeks, scrupulously controlling what they ate. His idea was to avoid the biases of typical diet studies that rely on people’s self-reports, which rarely match what they truly eat. The investigator, who has a physics doctorate, has that discipline’s penchant for precise measurements. His first study found that, contrary to many predictions, a diet that reduced carb consumption actually seemed to slow the rate of body fat loss. The second study, published this year, identified a new reason for weight gain. It found that people ate hundreds more calories of ultraprocessed than unprocessed foods when they were encouraged to eat as much or as little of each type as they desired. Participants chowing down on the ultraprocessed foods gained two pounds in just two weeks.“Hall’s study is seminal—really as good a clinical trial as you can get,” says Barry M. Popkin, a professor of nutrition at the University of North Carolina at Chapel Hill, who focuses on diet and obesity. “His was the first to prove that ultraprocessed foods are not only highly seductive but that people tend to eat more of them.” The work has been well received, although it is possible that the carefully controlled experiment does not apply to the messy way people mix food types in the real world.
The man who designed the research says he is not on a messianic mission to improve America’s eating habits. Hall admits that his four-year-old son’s penchant for chicken nuggets and pizza remains unshakable and that his own diet could and probably should be improved. Still, he believes his study offers potent evidence that it is not any particular nutrient type but the way in which food is manipulated by manufacturers that plays the largest role in the world’s growing girth. He insists he has no dog in any diet wars fight but is simply following the evidence. “Once you’ve stepped into one camp and surrounded yourself by the selective biases of that camp, it becomes difficult to step out,” he says. Because his laboratory and research are paid for by the national institute whatever he finds, Hall notes that “I have the freedom to change my mind. Basically, I have the privilege to be persuaded by data.” (...)
Processed Calories
Hall likes to compare humans to automobiles, pointing out that both can operate on any number of energy sources. In the case of cars, it might be diesel, high-octane gasoline or electricity, depending on the make and model. Similarly, humans can and do thrive on any number of diets, depending on cultural norms and what is readily available. For example, a traditional high-fat/low-carb diet works well for the Inuit people of the Arctic, whereas a traditional low-fat/high-carb diet works well for the Japanese. But while humans have evolved to adapt to a wide variety of natural food environments, in recent decades the food supply has changed in ways to which our genes—and our brains—have had very little time to adapt. And it should come as no surprise that each of us reacts differently to that challenge.
At the end of the 19th century, most Americans lived in rural areas, and nearly half made their living on farms, where fresh or only lightly processed food was the norm. Today most Americans live in cities and buy rather than grow their food, increasingly in ready-to-eat form. An estimated 58 percent of the calories we consume and nearly 90 percent of all added sugars come from industrial food formulations made up mostly or entirely of ingredients—whether nutrients, fiber or chemical additives—that are not found in a similar form and combination in nature. These are the ultraprocessed foods, and they range from junk food such as chips, sugary breakfast cereals, candy, soda and mass-manufactured pastries to what might seem like benign or even healthful products such as commercial breads, processed meats, flavored yogurts and energy bars.
Ultraprocessed foods, which tend to be quite high in sugar, fat and salt, have contributed to an increase of more than 600 available calories per day for every American since 1970. Still, although the rise of these foods correlates with rising body weights, this correlation does not necessarily imply causation. There are plenty of delicious less processed foods—cheese, fatty meats, vegetable oil, cream—that could play an equal or even larger role. So Hall wanted to know whether it was something about ultraprocessing that led to weight gain. “Basically, we wondered whether people eat more calories when those calories come from ultraprocessed sources,” he says. (...)
A Gut-Brain Disconnect
Why are more of us tempted to overindulge in egg substitutes and turkey bacon than in real eggs and hash brown potatoes fried in real butter? Dana Small, a neuroscientist and professor of psychiatry at Yale University, believes she has found some clues. Small studies the impact of the modern food environment on brain circuitry. Nerve cells in the gut send signals to our brains via a large conduit called the vagus nerve, she says. Those signals include information about the amount of energy (calories) coming into the stomach and intestines. If information is scrambled, the mixed signal can result in overeating. If “the brain does not get the proper metabolic signal from the gut,” Small says, “the brain doesn’t really know that the food is even there.”
Neuroimaging studies of the human brain, done by Small and others, indicate that sensory cues—smells and colors and texture—that accompany foods with high-calorie density activate the striatum, a part of the brain involved in decision-making. Those decisions include choices about food consumption.
And that is where ultraprocessed foods become a problem, Small says. The energy used by the body after consuming these foods does not match the perceived energy ingested. As a result, the brain gets confused in a manner that encourages overeating. For example, natural sweeteners—such as honey, maple syrup and table sugar—provide a certain number of calories, and the anticipation of sweet taste prompted by these foods signals the body to expect and prepare for that calorie load. But artificial sweeteners such as saccharin offer the anticipation and experience of sweet taste without the energy boost. The brain, which had anticipated the calories and now senses something is missing, encourages us to keep eating.
To further complicate matters, ultraprocessed foods often contain a combination of nutritive and nonnutritive sweeteners that, Small says, produces surprising metabolic effects that result in a particularly potent reinforcement effect. That is, eating them causes us to want more of these foods. “What is clear is that the energetic value of food and beverages that contain both nutritive and nonnutritive sweeteners is not being accurately communicated to the brain,” Small notes. “What is also clear is that Hall has found evidence that people eat more when they are given highly processed foods. My take on this is that when we eat ultraprocessed foods we are not getting the metabolic signal we would get from less processed foods and that the brain simply doesn’t register the total calorie load and therefore keeps demanding more.”
Image: Jamie Chung (photo); Amy Henry (prop styling); Source: “NOVA. The Star Shines Bright,” by Carlos A. Monteiro et al., in World Nutrition, Vol. 7, No. 1; January-March 2016
