When a person’s weight is higher than what is typically recognized as healthy for their height, that person is overweight or obese. Overweight and obesity are defined as abnormal or excessive fat accumulation that may impair health.

The way we have historically identified overweight and obesity is using a measure known as body mass index (BMI). BMI is a simple weight for height index defined as a person’s weight (in kilograms) divided by the square of height in meters.  

Understanding BMI

There is a link between BMI and body fat in men and women and more importantly, a correlation between BMI and mortality ratio. The higher the BMI, the higher the risk of death. That’s because obesity is more than extra weight – it’s a complex disease that can impact the whole body. The difference between being overweight and being obese is made by looking at the BMI and the relative mortality risk increase.

A person whose BMI is in the range of 18.5 to 24.9 is considered at normal weight; an overweight person has a BMI of 25 to 29.9. Obesity is 35 or more and is divided into three classes: obesity class I is defined for a BMI of 30 to 34.9, obesity class II has BMI 35 to 39.9, and class III obesity or morbid obesity is BMI of 40 or higher.

The National Center for Health Statistics estimates that, for 2017-2018 (the latest years available) in the United States, of adults age 20 and over, 42.5 percent were obese (including 9 percent with severe obesity), and 31.1 percent were overweight. Obesity rates have increased for all population groups in the United States over the last several decades.

Obesity is a complex disease

Obesity is a threat to health because it affects the whole body. Obesity and its complications are more deadly than cancer in the United States and are a cause of or are associated with multiple medical complications, including:

  • stroke
  • idiopathic intracranial hypertension
  • cataracts
  • obstructive sleep apnea
  • hypoventilation syndrome
  • coronary artery disease
  • pancreatitis
  • diabetes
  • dyslipidemia
  • hypertension
  • non-alcoholic fatty liver disease
  • gallbladder disease
  • polycystic ovarian syndrome
  • infertility
  • abnormal menses
  • cancer (breast, uterus, cervix, prostate, kidney, colon, esophagus, pancreas, liver)
  • osteoarthritis
  • gout
  • venous stasis

Metabolic syndrome

Obesity is also associated with what is known as metabolic syndrome, especially when there is the presence of increased fat (adipose tissue) in the abdomen. Metabolic syndrome is actually a cluster of conditions that can occur together, which then increase the risk of other medical conditions, such as risk of heart disease, stroke, type 2 diabetes and others.

A diagnosis of metabolic syndrome requires at least three of these conditions:
•    waist circumference over 40 inches for men or 35 inches for women
•    fasting glucose level of > 100 mg/dL or need for medications
•    triglycerides of >150 mg/dL or need for medications
•    HDL cholesterol level < 40 mg/dL for men) or < 50 for women, or need for medications
•    blood pressure > 130 mmHg systolic or > 85 mmHg diastolic, or need for medications

The myth of "healthy obesity"

Obesity is associated with a reduced life expectancy, largely because obese individuals are at increased risk of so many medical complications. But not all obese individuals are the same, and some do not have the metabolic abnormalities that often accompany obesity.

Obesity is a multifactorial disorder, meaning it is influenced by a wide variety of factors, including genetic, behavioral, lifestyle and environmental factors. In addition, fetal programming, control of appetite and energy expenditure, and availability and nutritional content of food also play a role.
Metabolic healthy obesity is not a benign condition long term. There is research that 30 to 40 percent of obese individuals will eventually develop metabolic complications after six years of follow-up. The idea of “healthy obesity” is not a static condition, and patients who do not yet have metabolic complications have to change lifestyle and eating habits. This will help prevent these complications from developing, because these patients are still at higher morbidity and mortality risk compared to the general population.

Getting healthier

Because so many factors play a role in obesity, treatment must be multidisciplinary. The first step is self-assessment and making behavioral and lifestyle modifications. This can be followed by a more structured and personalized exercise and nutrition plan.

Unfortunately, many patients who are overweight or obese have years of trying dieting programs and exercising. Despite the years-long efforts, some cannot achieve the desired results.

We now know that obesity is not just a disease treated by effort, as our society tries to force us to believe. These patients need extra tools to achieve healthy weight, and bariatric surgery, together with a comprehensive lifestyle change program is often the only way to achieve long term results.

Learn more about our Center for Bariatric Surgery and how we can help you on your journey to a healthier future.

Marcoandrea Giorgi, MD

Marcoandrea Giorgi, MD

Dr. Marcoandrea Giorgi is a bariatric surgeon with the Center for Bariatric Surgery and an assistant professor of surgery at The Warren Alpert Medical School of Brown University.