There are many reasons why some people have trouble losing weight. But often, obesity results from inherited, physiological and environmental factors, combined with diet, physical activity and exercise choices one makes.

Causes

Thier are many reasons of gaining too much weight but there might be genetic, behavioral, metabolic and hormonal influences on body. Mostly obesity occurs when one takes more calories than it burns through typical daily activities and exercise. Your body stores these excess calories as fat.

Most people's diets are too high in calories — often from fast food and high-calorie beverages. People with obesity might eat more calories before feeling full, feel hungry sooner, or eat more due to stress or anxiety.

Many people who live in Western countries now have jobs that are much less physically demanding, so they don't tend to burn as many calories at work. Even daily activities use fewer calories, courtesy of conveniences such as remote controls, escalators, online shopping, and drive-through restaurants and banks.

Certain diseases and medications

In some people, obesity can be traced to a medical cause, such as hypothyroidism, Cushing syndrome, Prader-Willi syndrome and other conditions. Medical problems, such as arthritis, also can lead to decreased activity, which may result in weight gain.

Some medicines can lead to weight gain if you don't compensate through diet or activity. These medicines include steroids, some antidepressants, anti-seizure medicines, diabetes medicines, antipsychotic medicines and certain beta blockers.

Social and economic issues

Social and economic factors are linked to obesity. It's hard to avoid obesity if you don't have safe areas to walk or exercise. You may not have learned healthy ways of cooking. Or you may not have access to healthier foods. Also, the people you spend time with may influence your weight. You're more likely to develop obesity if you have friends or relatives with obesity.

Age

Obesity can occur at any age, even in young children. But as you age, hormonal changes and a less active lifestyle increase your risk of obesity. The amount of muscle in your body also tends to decrease with age. Lower muscle mass often leads to a decrease in metabolism. These changes also reduce calorie needs and can make it harder to keep off excess weight. If you don't consciously control what you eat and become more physically active as you age, you'll likely gain weight.

Other factors

• Pregnancy. Weight gain is common during pregnancy. Some women find this weight difficult to lose after the baby is born. This weight gain may contribute to the development of obesity in women.


• Quitting smoking. Quitting smoking is often associated with weight gain. And for some, it can lead to enough weight gain to qualify as obesity. Often, this happens as people use food to cope with smoking withdrawal. But overall, quitting smoking is still a greater benefit to your health than is continuing to smoke. Your health care team can help you prevent weight gain after quitting smoking.


• Lack of sleep. Not getting enough sleep can cause changes in hormones that increase appetite. So can getting too much sleep. You also may crave foods high in calories and carbohydrates, which can contribute to weight gain.


• Stress. Many external factors that affect mood and well-being may contribute to obesity. People often seek more high-calorie food during stressful situations.


• Microbiome. The make-up of your gut bacteria is affected by what you eat and may contribute to weight gain or trouble losing weight.

Even if you have one or more of these risk factors, it doesn't mean that you're destined to develop obesity. You can counteract most risk factors through diet, physical activity and exercise. Behavior changes, medicines and procedures for obesity also can help.