Being obese doesn’t necessarily mean you will develop physical changes that cause diabetes, heart disease, and stroke, according to a new study.
Researchers at the Washington University School of Medicine in St. Louis, have found there is a “subset” of obese people do not have common metabolic abnormalities related to obesity. Those abnormalities are insulin resistance, abnormal blood lipids (high triglycerides and low HDL cholesterol), high blood pressure, and excess liver fat.
The subset of people who didn’t have the metabolic abnormalities at the start of the study didn’t get them even after gaining weight.
In the study, 20 obese participants were asked to eat 1,000 extra calories daily until they had gained about six percent of their body weight – or about 15 pounds over several months. Then researchers tested them to see how their metabolic function was affected by the weight gain.
The participants ate at fast-food restaurants and were supervised by a dietician. Before and after weight gain, researchers recorded each subject’s body composition, insulin sensitivity, and ability to regulate blood sugar, liver fat, body composition, and other measures of metabolic health.
The metabolic outcomes of the participants stayed within the normal range if they were normal when the study began. But metabolic measures got worse in obese subjects who gained weight and whose metabolic profiles were abnormal in the beginning of the study.
“This research demonstrates that some obese people are protected from the adverse metabolic effects of moderate weight gain, whereas others are predisposed to develop these problems,” says senior investigator Samuel Klein, MD, the Danforth Professor of Medicine and Nutritional Science and director of Washington University’s Center for Human Nutrition, in a news release.
“This observation is important clinically because about 25 percent of obese people do not have metabolic complications,” he adds. “Our data shows that these people remain metabolically normal even after they gain additional weight.”
After they had gained the weight, the researchers worked with participants to help them lose the weight they’d gained.
“It’s important to point out that once the study was completed, we enrolled all subjects in our weight-loss program to make sure they lost all of the weight they had gained, or more,” says Klein, who also directs the Division of Geriatrics and Nutritional Science and the Atkins Center of Excellence in Obesity Medicine.
Subjects who had abnormal metabolism also had fat inside their livers. Neither did they express genes to regulate fat production and accumulation.
“These results suggest that the ability of body fat to expand and increase in a healthy way may protect some people from the metabolic problems associated with obesity and weight gain,” says Klein.
He adds that obesity plays a part in more than 60 different unhealthy conditions.
“We need more studies to try to understand why obesity causes specific diseases in some people but not in others,” Klein says. “Could it be genetics, specific dietary intake, physical lifestyle, emotional health or even the microbes that live in the gut?”
The researchers plan to more closely analyze fat, muscle, and liver tissue in participants in further studies, and they plan to include lean people to learn more about why some people are protected from metabolic problems and why others are more susceptible.