Obesity is not all about looks—it’s a serious, chronic disease that affects millions of people across the globe. But knowing that obesity puts us beyond the realm of willpower and lifestyle. It is influenced by an intricate mix of genetics, biology, behavior, and environment.
Diagnosis of obesity typically begins with something referred to as body mass index, or BMI. It is a quick calculation that divides your weight by your height. In most grown-ups, a BMI of 30 or higher is considered obese, and a BMI of 40 or higher is in what is now referred to as class III obesity (formerly morbid obesity). All that being said, BMI is not a measurement in its own right. A very muscular person could technically fall under the obese category even if they have very little fat, and certain populations—such as many Asians—may be at risk for health issues with lower BMIs. A secondary helpful metric is waist circumference. Having excess fat in the abdominal area is especially dangerous, and waist circumferences over 40 inches in men and 35 inches in women can be a warning sign.
At its simplest, obesity occurs when we consume more calories than we expend—but why that is, is not so simple. Genetics can have an impact on how our bodies absorb fat, how hungry we become, and how fast we metabolize calories. Food and exercise habits within a family also play a huge role. Medical conditions such as hypothyroidism or polycystic ovary syndrome (PCOS) bring on weight gain. Some drugs, some of which are used to treat depression, psychosis, diabetes, and inflammation, also impact weight by altering metabolism or appetite.
Diets filled with high-calorie foods, sweetened beverages, and large portions—particularly fast food—can cause weight gain over time. Add to that a lack of physical activity, which is common with desk jobs and screen-heavy routines, and you’ve got a recipe for fewer calories burned throughout the day. Sleep and stress also matter. Not getting enough quality sleep or living with constant stress can throw off your hunger hormones, making it easier to overeat and store fat.
The world around us also has a profound impact on our health. Residents of areas with no parks, sidewalks, or health food stores often struggle to be active or eat well. Tight budgets can lead folks toward lower-cost, high-calorie foods. Cultural norms and advertising can influence us to make unhealthy choices, and even the microbes in our gut—influenced by what we eat—may affect how our bodies deal with weight.
Obesity can strike anyone, from young children to elderly individuals. As we get older, our bodies lose muscle mass naturally, which can decelerate metabolism and cause weight gain over time unless diet and activity levels are modified. Women can struggle to lose weight after pregnancy, and smoking cessation, while beneficial for all-around health, can at times cause temporary weight gain because individuals turn to food for comfort.
The medical risks associated with obesity are severe. It can raise the chance of heart attacks and strokes by contributing to high blood pressure and poor cholesterol levels. It can interfere with how your body uses insulin, increasing the risk for type 2 diabetes. People with obesity are also at greater risk for several types of cancer, including breast, colon, and liver cancer. Other problems—like joint pain, digestive issues, sleep apnea, and liver disease—are more common too.
Aside from physical well-being, obesity can strongly influence emotional well-being and quality of life. It can make routine tasks more difficult, reduce mobility, and cause social stigma or discrimination. Depression, anxiety, and low self-esteem also plague many individuals with obesity. Fertility problems may ensue, especially in more severe cases of obesity.