What It Is, Classes, Symptoms, Causes

What are the symptoms of obesity?

While obesity is a disease, it doesn’t cause specific symptoms. A healthcare provider may define obesity by calculating your:

• Body mass index: The BMI measures average body weight against average body height. Healthcare providers use BMI to classify obesity.
• Body shape: Providers may measure your waist circumference.

BMI classifications

Healthcare providers classify obesity by your BMI. There are three general classes of obesity that providers use to decide what steps you can take to lose weight. Those classes are:

• Class I obesity: BMI 30 to less than 35 kg/m² (kilograms per square meter).
• Class II obesity: BMI 35 to less than 40 kg/m².
• Class III obesity: BMI 40+ kg/m².

When you think about the BMI scale, it’s important to remember the BMI scale doesn’t accurately predict specific health risks.

Waist circumference

Where you carry extra weight may be a sign that you have more risk of health issues that obesity may cause. The U.S. Centers for Disease Control and Prevention (CDC) says a waist circumference of more than 35 inches in people assigned female at birth (AFAB) or 40 inches in people assigned male at birth (AMAB) can be a risk factor for cardiovascular disease or Type 2 diabetes.

What causes obesity?

On the most basic level, obesity happens when you consume more calories than your body can use. Many things may play a role in why you may eat more food than your body needs:

• Certain medications: Medications you take to treat other conditions may contribute to weight gain. Examples are antidepressants, steroids, anti-seizure medications, diabetes medications and beta-blockers.
• Disability: Adults and children with physical and learning disabilities are most at risk for obesity. Physical limitations and lack of adequate specialized education and resources can contribute.
• Eating habits: Consuming more calories than your body needs, eating ultra-processed food, high-sugar foods and drinks, and foods with high amounts of saturated fat may cause overweight.
• Genetics: Research shows people with obesity carry specific genes (obesity-susceptibility genes) that affect appetite. It’s not clear if people with overweight have the same genetic makeup.
• Lack of physical activity: High amounts of screen time — like watching TV, playing video games or spending time on your mobile phone or laptop — cut into the time you have for physical activity.
• Lack of sleep: Missing out on at least seven hours of sleep can affect the hormones that keep hunger urges under control.
• Stress: Your brain and body react to stress by making more hormones like cortisol that manage hunger. When you’re stressed, you’re more likely to eat high-fat, high-sugar food (comfort food) that your body stores as extra fat.
• Underlying health issues: Diseases like metabolic syndrome and polycystic ovary syndrome can cause side effects like weight gain. Mental health issues like anxiety and depression can lead to eating high-calorie foods that activate the pleasure centers in your brain.

What are the complications of obesity?

Obesity affects your body in many ways. For example, it may cause metabolic changes that increase your risk of serious illnesses. Obesity may also have direct and indirect effects on your overall health.

Metabolic changes

Your metabolism is how your body converts calories into energy to fuel your body. When your body has more calories than it can use, it converts the extra calories into lipids and stores them in your body fat. When you run out of tissue to store lipids, the fat cells themselves become enlarged. Enlarged fat cells secrete hormones and other chemicals that cause inflammation.

Inflammation can lead to insulin resistance so your body can’t use insulin to lower the sugar and fats in your blood. High levels of sugar and fats in your blood lead to high blood pressure. Combined, these conditions lead to metabolic syndrome. Metabolic syndrome is a common factor in obesity. The syndrome also increases your risk of developing diseases like:

• Cardiovascular diseases: Having obesity increases your risk for cardiovascular diseases, including coronary artery disease, congestive heart failure, heart attack and stroke.
• Fatty liver disease: Excess fats circulating in your blood make their way to your liver, which is responsible for filtering your blood. When your liver begins storing excess fat, it can lead to chronic liver inflammation (hepatitis) and long-term liver damage (cirrhosis).
• Gallstones: Higher blood cholesterol levels can cause cholesterol to accumulate in your gallbladder, which increases your risk of cholesterol gallstones and gallbladder diseases.
• Kidney disease: High blood pressure, diabetes and liver disease are among the most common contributors to chronic kidney disease.
• Type 2 diabetes: Having obesity specifically raises your risk of Type 2 diabetes.

Statistically, obesity increases your risk of premature death from all causes. Studies show you can reduce that risk by losing even a small amount (5% to 10%) of your current weight.

Direct effects

Excess body fat can crowd the organs of your respiratory system and put stress and strain on your musculoskeletal system. This contributes to:

• Arthritis.
• Asthma.
• Back pain.
• Obesity hypoventilation syndrome.
• Sleep apnea.

Having obesity increases your risk of conditions and diseases like: