The Health Impacts of Obesity

Dr. Tzvi Doron
March 19, 2018

The Health Impacts of Obesity

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Obesity might be one of the 21st century’s defining epidemics. In fact, the World Health Organization (WHO) considers obesity a “pandemic” (a worldwide disaster), estimating that 650 million adults are obese and another 1.9 billion are overweight. Closer to home, the CDC estimates that 1 in 3 adults over age 20 have obesity, 2 in 3 adults in the US are overweight or obese.

More than 70% of US adults over age 20 are overweight or obese

What do statistics like that even mean? What happens when the majority of a population suffers from an epidemic like obesity? Short answer: Millions of people have an increased risk for life-threatening health conditions. To understand exactly how obesity affects your health, we take a closer look at how we define obesity, some of the major health impacts of obesity, and what you can do if you’re one of the millions of overweight or obese Americans.

Obesity is Officially a Disease

In 2013, the American Medical Association (AMA) officially categorized obesity as a disease. Before that, “obesity” wasn’t even technically a medical condition. It was simply a “risk factor” for conditions like heart disease and diabetes. Doctors had to treat the symptoms of obesity—which we’ll get into those in a minute—but not the root cause of a lot of adverse health outcomes. Thankfully, that stance is changing.

Classifying obesity as a “disease” changes everything about the way medical professionals discuss, diagnose, and treat patients with this serious condition. Obesity isn’t just another risk factor anymore. It’s a life-threatening disease. And that medical distinction should change the way you think about obesity, too.

Defining Obesity: BMI

obesity BMI

But what is obesity? How do you know if you’re obese, overweight, or just “big-boned?” The WHO, CDC, and pretty much everyone else answers this question using one simple measurement—Body Mass Index (BMI). The great thing about BMI is that it’s super simple. To find out your BMI, just divide your weight (in kgs) by your height (in meters, squared). Ta-da.

Then use that number to see if you are classified as underweight, normal weight, overweight, or obese:

  • Underweight: BMI<18.5
  • Normal Weight: BMI 18.5-24.9
  • Overweight: BMI 25-29.9
  • Obesity Class I: BMI 30-34.9
  • Class II: BMI 35-39.9
  • Class III: BMI>40

The Problem With BMI: Muscle Mass

If you’re skeptical about such an obviously simple obesity classification system, you’re not alone. BMI is simple. However, that’s part of why it’s great. Everyone can calculate their BMI with a scale and a tape measure. That’s awesome. However, the BMI formula—kg/m²— doesn’t take into account factors like lean muscle mass or beneficial body fat. In fact, many perfectly healthy people—even professional athletes in peak physical condition— are technically considered “obese” according to the BMI scale. Why? BMI isn’t an accurate measurement of obesity in people with very low or very high lean body mass.

Muscle weighs more than fat. So when you use “weight” as 50% of your obesity metric, you’re missing a lot of information. For example, just about every NFL player is overweight or obese according to their BMI, even though many of them are quite lean. And you don’t have to be a pro athlete to skew BMI results. Cyclists, rock climbers, Crossfit gurus, and even dancers often have “obese” or overweight BMIs thanks to their heavier, denser muscle mass. But before you decide to ignore BMI, remember that it’s just a starting point.

The simplicity and ease of use is exactly what makes BMI useful. And while it comes with some problems, your BMI is an important number to know. If you’re not a fan of BMI, there’s no shortage of other obesity tests.

Some researchers suggest replacing BMI with waist circumference (WC) or waist/hip ratio. These tests assess your abdominal obesity and visceral obesity (excess fat around the organs) to find the biggest risks to your health instead of a general metric of obesity. Nevertheless, BMI is the most widely used tool to diagnose obesity and it’s useful in most populations, at least as a signal for more evaluation.

The Health Effects of Obesity

Obesity generally acts on the body in two ways. So before we get into any specific conditions related to obesity, it’s worth pointing out how obesity affects your overall health:

  1. Physical Stress: Carrying excess weight on your skeletal structure (as well as other body systems), comes with serious negative effects on your overall health.
  2. Physiological Changes: Excess body fat (adiposity) fundamentally changes how certain systems in your body function. This includes increased inflammation, hormonal changes, and changes in blood pressure and cholesterol, among other effects.

This two-pronged health impact of physical stress and physiological changes are why health organizations like the CDC argue that obesity might be the biggest epidemic of our time. So let’s get into how each affects your health.

The Physical Stress of Obesity: Bones & Breathing

obesity and arthritis

The bones and muscles of the human body are designed to carry (and move) a certain amount of weight. And while the human body is incredibly resilient and adaptive, there are limits. The prolonged physical stress of carrying hundreds of pounds of weight takes a toll on your body—particularly your joints.

Obesity increases your risk for hip and knee osteoarthritis, as well as other musculoskeletal pain syndromes. But, the bad news doesn’t stop there. Obesity also increases your risk for hand arthritis—something that isn’t easily explained by an increased load on joints like your knees or hips. Obese people also have an increased risk of symptomatic arthritis (joint pain, aching, stiffness) as well as the need for joint replacements compared to their non-obese counterparts.

Weight loss improves both asthma and sleep apnea symptoms

Obesity also affects your respiratory system.

Excess body weight puts pressure on your lungs, diaphragm, and chest wall, as well as increasing your risk for obesity-related inflammation. In extreme cases obesity contributes to respiratory diseases like Obesity Hypoventilation Syndrome, which can result in heart failure. Obesity also increases your risk for asthma and obstructive sleep apnea (when your airway becomes obstructed in your sleep).

What really drives home the connection to obesity and respiratory problems is that both asthma and sleep apnea generally improve with weight loss.

Physiological Diseases Associated with Obesity

The physical aspects of excess weight on the skeletal and respiratory systems is only half the problem. Excess fat in your tissues and blood (adipose) causes significant chemical changes to how your body functions. Too much fat literally changes the chemical makeup of your body. One of the most prominent examples is visceral fat tissue.

Too many fat cells can physically alter your hormone levels

Enough visceral fat cells can act like part of the endocrine system (your hormone production) by actually secreting hormones like leptin and adiponectin, as well as inflammatory chemicals called cytokines (TNF alpha, IL-6, etc.). Enough of these chemicals can kickstart events that increase inflammation, blood pressure, blood clotting, and even the types of “bad” cholesterol that cause cardiovascular disease.

These fundamental chemical changes are responsible for many of the “increased risks” for diseases associated with obesity. If you’re obese or overweight you have an increased risk for the following diseases:

9 Diseases Associated with Obesity

Obesity: Heart Disease, Stroke & High Cholesterol

Obesity: Diabetes & Hypertension

Obesity: Fertility & Testosterone

  • Decreased Fertility: Obesity has also been shown to decrease sperm quantity and quality, which is responsible for decreased fertility in obese men. This is at least partially due to the inflammation and oxidative stress, which damages the sperm.
  • Low Testosterone: Obese men contain excessive amounts of an enzyme called aromatase which is responsible for converting testosterone to estrogen. This causes decreased testosterone due to excess estrogen and a decrease in testosterone production by the testicles.

Obesity decreases sperm count and lowers testosterone

Obesity: Cancer & Mortality

Treating Obesity: Diet

It seems obvious, but the best way to treat the health risks of obesity is to lose weight. Weight loss interventions in obese people appear to lower the risk of death. Guidelines from the American Heart Association, American College of Cardiology, and the Obesity Society claim that losing 5% or more of your total body weight has positively impacts many of the negative consequences associated with obesity. However, some conditions require more weight loss than others for any meaningful improvement.

Losing 5% of your body weight can have positive impacts on the health risks of obesity

The foundation of obesity treatment is lifestyle intervention—aka living healthier. That means eating a diet that achieves a caloric deficit (you burn more calories than you eat). You can do this with a low fat or low carb diet, or, if you’re feeling experimental, try something more adventurous like the Mediterranean Diet. The point is, there’s no one magic diet that works for everyone. We’re all different. The most important thing is to find a diet or strategy that you can stick to.

For some people that’s a low carbohydrate diet. For others it’s a low fat diet. Structured weight loss programs with regular, in-person (best) or online (also good) contact with a weight loss professional also increases the chances of success. So get more people involved. You’ll be surprised how accountability makes a difference.

Treating Obesity: Exercise


A lot of doctors recommend a minimum of 150 minutes of “moderate physical activity” every week, in addition to a reduced calorie diet. That may sound like a lot, but it’s only about 20 minutes a day. You can do that. The bad news is that keeping the weight off is typically more difficult than losing it in the first place.  In fact, many weight loss professionals recommend “200-300 minutes per week of moderate physical activity” (30-40 minutes a day) to stay at your goal weight. If that’s a hurdle for you, or you keep ballooning  up and down, there are some medication that may help.

Treating Obesity: Medication & Surgery

The FDA recently approved several medications to treat obesity, that can induce modest weight loss when added to a healthy diet and moderate exercise. These medications are recommended for people with a BMI of 30 or more, especially if you also have diabetes or hypertension. Ask your doctor if medication can help you manage your weight loss, but don’t rely on medication to do all the work. These medications can be very helpful in some people, I don’t recommend using them for weight loss without an aggressive lifestyle program in place.

Bariatric surgery can also be an option for more extreme cases of obesity. It’s currently recommended for people with a BMI of 40 or more. The two most common weight loss surgeries in the United States are Roux-En-Y Gastric Bypass (RYGB) and Sleeve Gastrectomy. RYGB has been shown to cause greater weight loss than sleeve gastrectomy, but comes with a higher complication rate. If you’re a candidate for bariatric surgery, you should discuss which option is best with your surgeon.

The Health Impacts of Obesity

Obesity is a complicated problem. The physical damage and chemical changes it creates in your body, aren’t just hard to diagnose—they’re difficult to treat. If you’re suffering from obesity, it’s important to know that weight loss and maintenance success is possible. Talk to your doctor about your options, and find a strategy that works for you, because obesity is a killer. Luckily, you can do something about it.

This information isn’t a substitute for professional medical advice, diagnosis, or treatment. You should never rely upon this article for specific medical advice. If you have any questions or concerns, please talk to your doctor.

Dr. Tzvi Doron is board certified family doctor and the Clinical Director of Roman. He’s a member of the American Osteopathic Association (AOA) and the American Academy of Family Physicians (AAFP).

Dr. Tzvi Doron

Dr. Tzvi Doron is board certified family doctor and the Clinical Director of Roman. He’s a member of the American Osteopathic Association (AOA) and the American Academy of Family Physicians (AAFP).

All stories by:Dr. Tzvi Doron

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Dr. Tzvi Doron

Dr. Tzvi Doron is board certified family doctor and the Clinical Director of Roman. He’s a member of the American Osteopathic Association (AOA) and the American Academy of Family Physicians (AAFP).

All stories by:Dr. Tzvi Doron