The first step for solving a problem should be defining it. That's also true in the case of obesity. Research on obesity shows that this has become a global epidemic. In fact, recent studies indicate about one-third of Americans are obese. Yes that's right-one third! And it's highly unlikely that the situation will improve anytime soon. Here are some of the most common causes of obesity:

• Consuming too many calories

Water is the only natural food that has zero calories. All other foods have at least one. It's important to note that 3,500 calories equal one pound of weight. While you might not gain an extra pound of weight in a day, excess calories can add up and eventually lead to unwanted weight and fat. There are various ways to reduce your caloric intake. For instance, you could reduce your portion sizes during meals, or practice intermittent fasting.

• Lack of physical activity

In contrast with our hunter-and-gatherer ancestors, many of us spend most of our day seated. We even drive our vehicles around the block --to the mailbox or convenience store. By failing to burn a large chunk of the calories that we consume during the day, those calories will quickly transform into pounds and fat. The obvious solution is for us to get our rears in gear!

• Thyroid gland

The thyroid gland is the butterfly-shaped object located below the Adam's apple. What does it do? The thyroid gland is responsible for emitting hormones that basically control your metabolism. So when the thyroid gland is malfunctioning, this impacts your metabolism-and thus can result in an increase in body fat. Sometimes doctors overlook the impact on one's obesity, and may attribute the problem to other factors.

• Depression

When we feel depressed, one of the most common coping mechanisms is to eat our favorite "comfort foods." We eat in an attempt to fill the emotional void that we feel. Of course, overeating doesn't properly deal with the root cause of the depression. Also, the comfort foods that we tend to eat when we're feeling the blues can make the situation worse. For instance, fat-laden foods can cause us to feel sluggish.

• Genes

While researchers have been unable to uncover the "fat gene," clinical studies indicate that there is a strong link between obesity and genetics. Family members can indeed share genes that can cause multiple members of the family to become obese. However, it is important to remember that the diet and lifestyle habits of a family are also contributing factors.

• Metabolic syndrome

This is actually a group of conditions. When combined, they increase a person's likelihood of acquiring various cardiovascular diseases, and type-2 diabetes. Metabolic syndrome is a serious condition that can affect both humans and children. It results in several symptoms, including abdominal obesity.

The causes of obesity are quite varied. These aforementioned ones are some of the most common ones, and can have a major impact on one's risk of becoming obese. The key is to find the root cause of the obesity, and then solve the problem.