Contemplate a sweet, creamy milkshake, piled high with whipped cream and flavored with intensely rich dark chocolate syrup. Hard to resist, isn't it? Now a new study reveals the reason: It's the sugar, not the fat, that drives our food cravings and results in weight gain, reported the National Geographic on Dec. 17.
To conduct the study, researchers analyzed brain activity in more than 100 high school students as they drank chocolate-flavored milkshakes that were the same in calories but high in sugar, low in fat or low in sugar, high in fat.
Although both shakes appealed to the brains' pleasure centers in the students, the sugary shakes were much more effective at pinging the network that causes compulsive eating. Sugar is so powerful that it trumped the fat significantly, discovered Eric Stice, the lead author of the study, which was funded by the National Institutes of Health and published in The American Journal of Clinical Nutrition.
"It seems to be the case that we have a stronger inborn preference for sugar. In early times, we died from not having enough food. The preference makes sure you get enough calories. There is absolutely no brake on overconsumption," said Dr. Stice.
In addition, the research may point to the reason that several studies have discovered diets high in fat and protein that eliminate sugar, such as the Atkins diet and the Paleo diet, succeed better overall in weight loss.
Dr. Stice said that the human brain is designed to prefer sweet flavors to fat. When we're young, we prefer sugary foods. For that reason, diets that cut out sugar are easier to follow because they don't include foods that cause us to crave more.
“We do a lot of work on the prevention of obesity, and what is really clear not only from this study but from the broader literature over all is that the more sugar you eat, the more you want to consume it,” said Dr. Stice, a senior research scientist at the Oregon Research Institute, in an interview with the New York Times.
“As far as the ability to engage brain reward regions and drive compulsive intake, sugar seems to be doing a much better job than fat," he explained.
The research points to sugary foods as the culprits in the obesity epidemic, not plant-based, natural foods, said faculty member Nicole Avena, a faculty member at the New York Obesity Research Center at Columbia University.
“The obesity epidemic and the problems with overeating don’t have too much to do with people overeating fruits and healthy foods. They have a lot to do with people overeating excess sugars and fats,” added Dr. Avena.
But some health experts, such as physician Daniela Drake, go one step further. She contends that the answer to the obesity epidemic, shown by research, is a set of guidelines recommending ketogenic, high protein, high fat diets that eliminate sugar. (Get the details on how high fat, high protein, low carb ketogenic diets work by clicking here.)
Dr. Drake cites the case of a patient suffering from various symptoms to whom she prescribed an Atkins-style low carb, high fat, high protein diet.
"What happened next won’t surprise anyone who’s ever been on the Atkin’s diet: My patient lost weight and her sugars got better. Even her asthma went away. Completely. That low-carb-high-fat (LCHF) diet saved her life," says Dr. Drake.
However, the government's recommendation to cut calories and fat "could very well serve to make a nation of fat people even fatter. This is, after all, exactly what obese people tell us—the more they diet, the fatter they get," she noted.
And a growing number of health experts agree.
“While low-fat eating has increased, so have body weight and waistlines,” says Kerry Stewart, Professor of Medicine and Director of Clinical and Research Exercise Physiology at Johns Hopkins. “Based on what we know now about high carbohydrate eating, the obesity epidemic was predictable."
Learn about how researchers at UCSF are studying high fat, low carb diets by clicking here.