The greatest threat to any species has always been starvation.
When humans had to forage for their greens and hunt for their proteins, a little extra meat on a person’s bones meant things were good.
The biology of modern humans evolved under that model, but now that there’s an abundance of available calories, eating too much is a threat to the more than one third of Americans who are obese.
Dr. Christopher N. Ochner, an assistant professor of pediatrics and psychiatry at the Icahn School of Medicine at Mount Sinai in New York, argues these biological underpinnings help explain why obesity is nearly impossible to overcome by simply eating less and exercising more.
“We’re still designed to consume as many calories as possible,” Ochner told Healthline. “There hasn’t been enough time to change our biology.”
The Biological Effects of Obesity
In a new paper in the journal The Lancet, Ochner and colleagues argue that restricting calories triggers several biological adaptations designed to prevent starvation.
“These adaptations might be potent enough to undermine the long-term effectiveness of lifestyle modification in most individuals with obesity, particularly in an environment that promotes energy overconsumption,” they wrote. “However, they are not the only biological pressures that must be overcome for successful treatment.”
In layman’s terms, when a person becomes obese, their body gets accustomed to its new weight. When a low-calorie diet begins, the body defends itself as if it’s in a famine, fighting not to give up its fat stores.
“They physiologically begin starving to death,” Ochner said. “For someone who has sustained obesity for a period of time, at that point, the higher body weight is also stamped in.”
Taking Biology Into Account When Fighting an Epidemic
The U.S. Centers for Disease Control and Prevention reports that almost 35 percent of adults and 17 percent of children in the United States are obese. That’s more than 91 million people.
Obesity — recognized as a disease by the American Medical Association — is when a person’s body mass index, or BMI, is greater than 30. It’s also directly linked to a higher incidence of disease and a shorter lifespan.
Recent research published in the journal Nature supports Ochner’s claim that obesity is not a simple matter of calories in vs. calories out. The Nature research suggests that obesity is influenced by 97 regions in the human genome.
Dr. Elizabeth Speliotes, an assistant professor of internal medicine at the University of Michigan Health System, says this new finding “clearly shows that predisposition to obesity and increased BMI is not due to a single gene or genetic change.”
"The large number of genes makes it less likely that one solution to beat obesity will work for everyone and opens the door to possible ways we could use genetic clues to help defeat obesity," Speliotes said in a statement.
Ochner says what doctors are doing now by encouraging patients to reduce their calorie consumption and increase their physical activity is good for keeping overweight patients from becoming obese. However, he says it’s not sufficient for treating obesity.
“Diet and exercise are important, but they won’t do the trick,” he said. “We’ve been basically trying to re-invent a square wheel.”
Other, more intensive methods such as bariatric surgery and medications are the only methods currently available that are proven to help obese people lose weight and keep it off, but “relatively few people have access to these things,” Ochner said.
While diet and exercise alone may not be enough to cure obesity, they are still two of the best ways to prevent it.
In their paper, the Mount Sinai researchers suggest doctors address obesity prevention with overweight patients and focus on their lifestyle choices.
For treating obesity, however, the researchers recommend considering biologically based treatment, including medication and surgery where appropriate. Doctors should also monitor and change their treatment strategy as necessary, and inform patients of the challenges that lie ahead.
“We urge individuals in the medical and scientific community to seek a better understanding of the biological factors that maintain obesity and to approach it as a disease that cannot be reliably prevented or cured with current frontline methods,” the paper concludes.
Considering the serious biological changes that occur in the bodies of obese people, Ochner said parents have an obligation to take their children’s weight seriously.
“Don’t damn your kids into being obese their entire lives,” he said.