Several risk factors for obesity, such as genetics, metabolism, and hormones, are outside your control. Depending on your circumstances, you may be able to reduce your risk of obesity by making certain lifestyle changes.

Overweight and obesity can gradually develop when you consume more calories than your body uses, creating an energy imbalance. If your body stores more fat than it can use, it can lead to weight gain.

However, the risk of overweight and obesity involves more than calorie intake. Your environment, social behaviors, and medical history can all play a role.

Your environment has a significant effect on your daily routines, community involvement, and overall lifestyle choices.

People living in rural areas, for example, often have greater distances between their places of residence and grocery stores, healthcare facilities, and recreational areas or activities.

This can make it more difficult for residents to adopt or maintain habits that can help reduce the risk of obesity.

In the United States, access to affordable, healthy food differs by ethnicity, race, and income. Older research suggests that there are approximately 30% fewer supermarkets in minority-predominant and lower-income neighborhoods.

Areas with limited access to supermarkets (“food deserts”) tend to have a higher concentration of convenience stores and fast food restaurants with less nutritious food choices (“food swamps”).

Access to safe, well-maintained sidewalks and paths that encourage pedestrian travel between locations can also affect physical activity levels, which can influence weight.

These factors make up your “built environment.” Cultural norms and values — sometimes referred to as your “unbuilt environment” — can shape how you interact with your built environment.

For example, a parent or guardian’s beliefs and behaviors can affect a child’s dietary preferences and approach to physical activity.

Some people may be predisposed to gaining weight and developing obesity.

Your genes may influence how much fat you store in your body and where it’s distributed. They may also affect how effectively your body converts food into energy, regulates appetite, and burns calories during exercise.

According to a 2024 review, obesity genetics can be classified into syndromic and monogenic categories.

Syndromic obesity is often associated with neurodevelopmental delay or dysmorphic features. Examples include:

Monogenic obesity is primarily characterized by mutations involving a specific gene, such as:

  • leptin (LEP)
  • leptin receptor (LEPR)
  • proopiomelanocortin (POMC)
  • prohormone convertase 1 (PCSK1)
  • melanocortin 4 receptor (MC4R)

Weight gain is a side effect of certain medical conditions, including:

Conditions that affect or limit your ability to be physically active can lead to weight gain indirectly, including:

Some medications can stimulate your appetite, slow your metabolism, or affect how your body stores and absorbs nutrients, leading to unexpected weight gain.

Others may cause fatigue or weakness that interferes with your ability to be physically active.

This includes certain:

What you eat, how much you eat, and when you eat can affect your weight over time.

Behaviors that can contribute to weight gain include frequently:

In terms of dietary intake, this may look like eating or drinking excess amounts of:

Daily activities and exercise burn calories. Burning more calories than you consume through food and beverages can lead to weight loss, and burning less can lead to weight gain.

Being sedentary for extended periods — like working at a desk for 40 hours per week, for example — without engaging in regular physical activity can increase your risk of obesity and other health conditions.

According to the Centers for Disease Control and Prevention (CDC), adults should aim for at least 75 minutes of vigorous activity or at least 150 minutes of moderate activity per week.

How much sleep you get can affect the hormones that regulate your appetite. Leptin signals to your body that you’re full, while ghrelin tells your brain that you’re hungry.

If you don’t get enough sleep, leptin levels drop, causing your brain to signal hunger even when you don’t actually need food. Your ghrelin levels increase, intensifying feelings of hunger.

This can make it more difficult to recognize feelings of fullness and result in overeating. You may also crave foods that are high in carbohydrates, saturated fats, or added sugars, which can lead to weight gain if eaten in excess.

When you’re stressed, your body releases hormones that activate your “fight-or-flight” response. This shifts blood flow away from less essential processes, like digestion, to bodily functions that are key to your immediate survival.

The stress hormone cortisol raises blood sugar levels, providing quick energy to handle stress. Once the stressor is gone, blood sugar and insulin levels return to their previous state.

But if you experience chronic stress, your cortisol, blood sugar, and insulin levels remain high. This can lead to insulin resistance, increasing your risk of weight gain.

Increased cortisol can disrupt the production of other hormones, including corticotropin-releasing hormone (CRH), that influence your appetite.

Obesity is a complex condition that involves a variety of underlying factors. It usually can’t be attributed to a single cause. If you have questions or concerns about your weight, consider making an appointment with a healthcare professional to learn more.