Caroline Apovian, MD, codirector of the Center for Weight Management and Wellness at Brigham and Women’s Hospital, described some of the new insights about obesity she has gained during her talk at the annual meeting of the American College of Physicians.
“When I was a medical student a while back, I learned that fat tissue just sat there and stored fat,” she said. “Now we know it’s an endocrine organ.”
Dr. Caroline Apovian
This tissue secretes hormones, such as leptin, and other factors that have an array of effects on the brain, pancreas, heart, liver, and muscles. Moreover, it has plasticity, with the ability to change, constantly adjusting our metabolism as nutrient supply and demand changes, she continued.
Obesity leads to a decline in this plasticity, leading to fibrosis and inflammation and other problems. These changes can further impair the function of adipose tissue, leading to metabolic disease. But the central role of adipose tissue, and its dynamic nature, presents an opportunity for treatment, Dr. Apovian said, during her talk.
Hints to why obesity has become more common
More than 42% of the U.S. population – “unbelievably,” Dr. Apovian said – is obese, meaning they have a BMI over 30, according to the Centers for Disease Control and Prevention. That’s up by about 25% since 1960, although calories eaten hasn’t increased, and physical activity has increased somewhat, she said.
The root cause is still a bit of a mystery, but according to “good hints and clues” from animal models that are starting to be translated to the study of human obesity, “it has to do with epigenetics and how our brains and our bodies are perceiving the environment,” she noted, during her presentation.
“Our genes haven’t changed. Our environment has changed,” she said.
The industrialization of the food supply, the use of pesticides and preservatives, the dawn of fast food have all combined, most likely, to do “a number on our bodies,” Dr. Apovian said.
But not all hope is lost thanks to new research, Dr. Apovian suggested.
New treatments show promise for helping patients’ obesity
New research that has increased Dr. Apovian’s understanding of the sophisticated role of adipose tissue may be helpful for treating patients with obesity, offering more targets for intervention, she told the audience.
Some treatment avenues already identified have started producing results, Dr. Apovian noted.
Gastric bypass surgery typically leads to a loss of 25% of body weight, but is often shunned by patients, she said. “With such a great surgical procedure, we still only do 256,000 procedures and we have millions of Americans with a BMI over 30.”
Weight control with obsessive dieting, meal-planning and calorie-counting, “can be done, but it’s really hard,” Dr. Apovian noted.
More appealing therapies targeting hormones and appetite suppression have produced impressive results. Recently approved semaglutide produced 14% weight loss, compared with about 2% for placebo, she said.
Results just released for tirzepatide, a dual agonist of gut hormones GLP-1 and GIP, show a 22% total weight loss, compared with about 2% for placebo, with about 56% of patients losing more than 20% of their body weight, Dr. Apovian said.
Referencing studies finding that several hormones are altered during weight loss, she predicted that targeting multiple hormones with drug treatment will also be necessary for best results.
But, she noted, “we’re treating obesity now with one- or two-drug combos.”