Lifestyle, genetics, medicine, environment

Although historically thought to be primarily caused by excess caloric intake, obesity is a complex condition involving many factors. Approximately three out of every four adults in the United States are obese. Causes include hormones related to appetite and metabolism, which can be altered by the environment, medical conditions, genetics, and medications. The body’s collection of microorganisms, known as the microbiome, also plays a role.

Read on to learn more about obesity and its causes.

definition of obesity

The medical definition of obesity is a body mass index (BMI) of 30 kg/m2 or higher. BMI is calculated by dividing your weight (in kilograms) by your height (in square meters) to determine your weight for your height. However, using BMI can be problematic because weight does not directly correlate to body fat. This is important to understand when calculating and interpreting BMI.

For example, a very fit and muscular person will have a high BMI because muscle weighs more than fat. It also doesn’t necessarily mean you’re obese or at higher risk for obesity-related complications.

There are other methods to measure body fat, including dual-energy X-ray absorption (DEXA), underwater weighing, and bioelectrical impedance. However, these methods are not as widely available as his BMI measurements. Measuring skin fold thickness using calipers is an alternative method, but it may be difficult to standardize. Although BMI is a simpler and more easily measured method to screen for obesity, it remains a problematic measurement and may need to be reinterpreted in the appropriate context for the individual.

Causes of obesity related to lifestyle habits

Obesity is usually thought to be caused by the behavior of eating too many calories without consuming enough. While it is true that not consuming the calories you eat for a long period of time will lead to weight gain, this simplistic explanation does not take into account the role of biology and environment. Not everyone absorbs, stores, and expends energy in exactly the same way, and the hormones associated with metabolism vary from person to person.

Researchers are still discovering the exact causes and contributing factors to obesity. However, it cannot be denied that certain lifestyle habits have a significant impact on obesity. Imbalances in food intake and activity are thought to be one of the biggest causes of weight gain.

diet

Diet is the main cause of obesity. Eating high-calorie foods and diets high in saturated fat and refined sugars, especially processed foods, are associated with weight gain and obesity. A study of the world’s population found that increased soda consumption among adolescents was associated with a higher prevalence of obesity.

One 12-ounce can of soda contains about 40 grams (about 10 teaspoons!) of sugar, so it’s not hard to see why. Processed snack foods are rich in combinations of salt and saturated fat or refined sugars, and studies suggest that this high-calorie combination may alter appetite signals and lead to addiction-like and withdrawal behaviors. It has been.

activity

Another major cause of obesity is a sedentary lifestyle. The more time you spend sitting, the less calories you burn, and the less time you spend doing physical activities that burn more calories. A sedentary lifestyle is associated with obesity and chronic diseases such as diabetes, heart disease, and high blood pressure.

On the other hand, regular physical activity such as brisk walking, jogging, swimming, and moderate-intensity exercise such as aerobic sports has many health benefits, including helping you maintain your goal weight.

sleep

Sleep quality and duration also appear to influence obesity. Sleeping less than seven hours a night is associated with weight gain and obesity, and researchers suggest this may be related to the effects sleep deprivation has on appetite-related hormones. Additionally, there is evidence to suggest a link between weight gain and disruption of circadian rhythms, which means the body is awake at times during the body’s sleep/wake cycle, such as in people who work night shifts.

stress

Long-term stress levels can also affect weight gain and contribute to obesity. Chronic stress can be due to a variety of causes, but is associated with obesity. Stress increases the amount of stress hormone (cortisol) in your body, which can lead to weight gain over time. Additionally, the way you deal with stress can also affect your weight in some cases. For example, overeating (or “stress eating”) contributes to excess calories and potential weight gain.

genetic causes of obesity

If your parents are obese, you are more likely to be obese too. This is partly related to family and lifestyle factors that tend to be similar. However, genetics also influence obesity. Researchers have discovered a number of genetic variations that can increase susceptibility to obesity. These include mutations in appetite regulation and energy balance, such as proteins and hormones that help us feel hungry and full.

Prader-Willi syndrome is a rare genetic disorder that causes an insatiable appetite in affected children. This leads to overeating and obesity. Bardet-Biedl syndrome is another rare genetic disease that affects the eyes and causes obesity starting in childhood.

Biological and medical factors that cause obesity

Several medical conditions can contribute to excess weight and obesity. Many of these are related to hormones involved in metabolism and appetite. And the influence of the gut microbiome on obesity is becoming increasingly recognized.

hypothyroidism

Hypothyroidism is a condition in which there is insufficient thyroid hormone circulating in the blood. Thyroid hormones are involved in many body processes, especially weight, energy levels, skin, hair and nail growth, and digestion.

When your body doesn’t have enough thyroid hormones, your energy levels decrease, weight gain, and can lead to obesity. However, the American Thyroid Association notes that much of the weight gain in hypothyroidism is related to salt and water retention, and you can expect to gain up to 10 pounds.

cushing syndrome

Cushing’s syndrome is caused by an excess of stress hormones (cortisol) in the body. This can occur if you are taking steroid medications or if your body produces too many hormones. Cortisol is involved in regulating blood pressure and blood sugar levels. People with Cushing syndrome often have excess fatty tissue in their abdomen and upper back.

polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a syndrome that causes cysts on the ovaries as well as hormonal changes such as insulin resistance and excess androgen hormones. There is a clear link between PCOS and obesity. Researchers believe this relationship is due to genetic and hormonal factors.

intestinal microbiota

There are more bacterial cells than human cells in the human body, and the population of these microorganisms in the gastrointestinal system is called the gut microbiome. Science shows that patterns in the gut microbiome are associated with obesity. The bacteria in our gut are influenced by our own behavior, medical conditions, and the environment.

Research suggests that the typical Western diet, which includes foods high in saturated fat and refined sugars, may also promote obesity through the effects this diet has on the gut microbiome.

Social factors of obesity

In addition to the biological and behavioral causes of obesity discussed above, there are also social causes of obesity. Although these social factors can influence behavior, it is important to recognize that:

Below are social factors associated with increased risk of obesity.

• income level
• education level
• access to healthcare
• Living in certain geographic locations (South and Midwest) and in certain urban and rural environments has less access to fresh food and recreational activities.
• Food availability – lack of economic means to purchase food, such as the proliferation of fast food restaurants and food insecurity. Food insecurity results in less access to fresh produce and a reliance on lower-cost options, often more calorie-dense options.
• Walkability of the neighborhood
• Work environments that can lead to increased sedentary behavior

summary

Obesity is a common condition and has many causes spanning behavior, biology, and environment. Diet and physical activity are the main factors, but stress and sleep also play a role. Biological factors such as genetics and medical conditions affect appetite, satiety, energy balance and metabolism. Finally, social and environmental factors may play a role beyond an individual’s direct control.