Obese but Healthy: Understanding the Exceptions

August 30, 2013

News Review From Harvard Medical School -- Obese but Healthy: Understanding the Exceptions

Heart disease and diabetes are more common in people who are obese. But not all obese people have the same risk, a new medical journal article points out. Increasing evidence shows that some people who are obese have normal cholesterol, blood pressure and blood sugar. Doctors say they are metabolically healthy, though obese. These people may be fit even though they are overweight. They may have a relatively small waist size compared with their overall size. And they may be less likely to have long-lasting inflammation in the body. The authors of the new article say a better definition of the condition is needed. This might help doctors target treatments to those who need them most. For example, healthy obese people might be better off avoiding weight-loss surgery, they say. Doctors still don't know why some obese people don't suffer the same health problems as others. Much more research needs to be done, the authors say. Knowing why some people escape health problems that are typical with obesity might help scientists develop drugs to protect others. The journal Lancet Diabetes & Endocrinology published the "personal view" article August 29. BMJ Group news wrote about it.

By Howard LeWine, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

Just yesterday a friend was telling me about his dad. His father is 89 years old. He has been over 300 pounds most of his life and eats 10 pounds of fatty cold cuts each week. But his blood sugar is normal, and his total cholesterol is 122 (a number far below the average American's).  His doctor tells him he has the heart of a 30-year-old.

How can this be, my friend asked? The new term for this condition is metabolically healthy obesity.

Not many obese people are fortunate enough to have this favorable condition. It means that despite being obese, a person has a risk of getting diabetes and heart disease that is no greater than someone of normal body weight. In fact, the risk may actually be lower.

Obesity is defined as a body mass index (BMI) of 30 or higher. BMI is a number that's based on the relationship between weight and height.

The reason that this subgroup of obese people doesn't have the same diabetes and heart disease risk is almost certainly genetic. Scientists have yet to discover which genes control it.

But we do know a lot about the profile of the metabolically healthy obese:

• Despite their weight, they tend to have smaller waist sizes than most obese people. A large waist means you carry more belly fat. Doctors call it visceral fat. More belly fat translates to a greater diabetes and heart disease risk.
• Their body cells have normal insulin sensitivity. This means the cells use insulin in a normal way to turn the glucose (sugar) in food into energy. Most obese people develop insulin resistance, when cells don't use insulin well. Insulin resistance is the first step toward type 2 diabetes.
• They tend to have lower total cholesterol levels and normal blood pressure.
• They don't show evidence of lasting, low-level inflammation, which is common in metabolically UN-healthy obese people. Long-term inflammation is linked with an increase in heart disease and stroke risk. A study published earlier this week confirmed the lower levels of inflammation in people who are obese but metabolically healthy.

What Changes Can I Make Now?

Too often we have looked at body weight as the most important factor related to overall health. Now we know that some obese people can be metabolically healthy. But that does not mean body weight doesn't matter.

My friend's father has metabolically healthy obesity. But the extra weight has contributed to severe osteoarthritis of his hips and knees. Every step is painful. So even his "good genes" don't protect him from all obesity-related health problems.

Metabolic health matters a lot, no matter how many pounds show up on your scale. You can improve your metabolic health even if you didn't inherit those "good genes."

• Stay physically active as much as possible during the day.
• Dedicate at least 30 minutes per day to exercise. Ideally, aim for 60 minutes each day.
• Eat a Mediterranean-style diet.
• Load up on fruits, vegetables and whole-grain foods.
• Eat healthy sources of protein, such as fish, nuts and beans.
• Avoid tobacco products.

What Can I Expect Looking to the Future? 

We have a lot to learn from the metabolically healthy obese. First, experts will need to agree on a specific definition. Researchers will look for the genes and other biological pathways that lead to this condition. And for the majority of obese people who are metabolically unhealthy, other lifestyle changes and new medicines might be discovered to improve their health.