Mass General obesity medicine expert, Lee Kaplan, MD, PhD, says that old, one-size-fits-all ideas about obesity are giving way to a new understanding that points towards more individualized treatment.

When he was a child, Lee Kaplan, MD, PhD, says, his mother was a tiny, effortlessly slim woman. Many decades later, he saw her gain a large amount of weight that she could not lose. He wondered what had changed. As founder of the Massachusetts General Hospital Weight Center and director of the Obesity, Metabolism and Nutrition Institute, Dr. Kaplan is working to answer such questions about the causes of obesity and the future of treatment. He recently discussed his work.

Why is it so hard for people to lose weight and keep it off?

The idea that obesity is caused simply by eating too many calories persists. Unfortunately, that’s not the right answer. It takes an understanding of complex biology to see it. Think about water. If you need water, your brain makes you thirsty and you drink. If you drink more than you need, your body gets rid of it.

Lee Kaplan, MD, PhD, obesity research
Lee Kaplan, MD, PhD, is working to individualize the treatment of obesity and related disorders.

It’s the same with calories and body fat. You can control it for a short time by eating less and you may lose weight. But if all you do is eat less, your body will eventually fight back. You’ll stop losing weight and ultimately your body will push you to regain all of what you lost.

Can we control our body fat?

The body sets its own goal, or “set point,” for fat. Fat is our fuel supply, the body’s gas tank. There are complex signals and mechanisms that make sure you have the right amount of fat in your “tank.” We think we can voluntarily control the balance by counting calories and burning them with exercise. But the body’s fat mass goal is determined by our genetics, age and the environment and is powerfully defended. That’s why, when someone loses weight by reducing calorie intake, they almost always gain it back eventually.

Why are people fatter today than they were in the past?

The modern environment contains the perfect storm of multiple factors pushing up the body’s fat mass goal. The brain receives biological signals from inside the body and outside, and it reacts to the environment we live in. These signals convince the unconscious brain that the ideal amount of fat is higher than it used to be, or higher than is healthy. But the specific environmental signals that raise the set point are different in each of us. That’s why there’s no one solution.

Our studies showed that the reason surgery is so effective is not that it makes the stomach smaller or prevents food absorption.

Are there different causes of obesity?

Many categories of things contribute: food composition, physical activity, medications, genetics, stress, sleep, and biological rhythms. Food is a major factor, but it’s not about how much you eat. It’s about the quality. Thousands of different substances in food send signals throughout our bodies and brains.

Today’s processed food doesn’t contain the same combinations of substances as the food our ancestors ate and it doesn’t send the same signals. Some drugs, stress, sleep deprivation and other factors can stimulate similar signals, raising the fat mass set point and causing weight gain.

What have you learned from studying surgery for obesity?

The Mass General Weight Center does bariatric surgery, including gastric bypass surgery and sleeve gastrectomy. These surgeries are very effective, but not for the reasons we once thought.

Our studies showed that the reason surgery is so effective is not that it makes the stomach smaller or prevents food absorption. It’s about the signals being sent to the brain. The surgery is changing those very signals that are caused by the modern food supply, sleep deprivation, stress or drugs that make you store more fat in the first place. Those signals, and there are hundreds of them working together, determine how much fat your body wants to store, and adjusts your appetite to achieve that goal.

We train our clinicians to see obesity as a disease with different causes and solutions appropriate for individual patients.

What are your research goals?

We hope that eventually, we will be able to induce the same changes without surgery. We are trying to understand what determines each person’s fat mass set point and are looking for biomarkers that tell us if somebody is at, above or below it.

We’re also trying to assess how drugs and surgery interact with each other to affect body weight. And we’re looking for things that could predict who will respond to which of the many available therapies.

How do clinicians work with patients at the Weight Center?

We train our clinicians to see obesity as a disease with different causes and solutions appropriate for individual patients. For one person the cause of obesity may be lack of sleep. For another, it may be stress or the hormonal changes of puberty, pregnancy or menopause. It’s not the same for everyone. For treatment, we try to identify lifestyle changes, medications, or sometimes surgery, that can best help and we are working toward personalizing treatment based on the causes of excess fat in each individual.

To learn more about obesity research and treatment, please contact us.