When people start noticing that they are putting on a few pounds, it is hard to tell at the time whether they see themselves becoming overweight or if they will end up suffering from obesity. While many may think that being overweight and obese are the same, that's not really correct.

Obesity is a disorder that involves the accumulation of excessive body fat and increases the risk of several health problems. Overweight, however, means having a weight more than normal or desirable.

Read: Chances Of Obesity Greater In US Women Than Men Because They Walk Less, Study Says

According to the National Health and Nutrition Examination Survey conducted between 2009 and 2010, more than two in three adults are considered to be overweight or obese. More than one in every three adults suffer from obesity, while more than one in 20 adults are considered to have extreme obesity. Among children and adolescents, about one-third of those aged between 6 and 19 are considered to be overweight or obese.

Obesity can be caused by consuming more calories than your body burns. The body stores unused calories as fat, leading to obesity. A person is believed to be overweight when his/her level of body fat based on height and weight is more than what it should normally be.

Excessive eating, drinking too much alcohol and not getting enough exercise can result in storing excess calories in one's body, which turns into excess fat, resulting in obesity.

Obesity Junk food is one of the leading causes of obesity. In this photo, a man eats a hamburger and chips in a cafe in Glasgow, Scotland, June 7, 2006. Photo: Getty Images/Jeff J Mitchell

Eating habits are not the only factors that contribute to excess weight gain, medical problems such as an underactive thyroid (hypothyroidism) or taking medication like birth control pills, antidepressants, and antipsychotics, could also be a cause.

"Energy balance in children happens when the amount of energy taken in from food or drink and the energy being used by the body support natural growth without promoting excess weight gain. Many factors can lead to energy imbalance and weight gain. They include genes, eating habits, how and where people live, attitudes and emotions, life habits, and income," according to the National Institutes of Health.

Body Mass Index (BMI) is usually used to determine excess body weight. A person is considered obese when BMI is over 30, while BMI between 25 and 29.9 indicates overweight. BMI between 18.5 and 24.9 means an adult is in a healthy weight range. BMI less than 18.5 indicates underweight.

There are several health risk factors linked to obesity and overweight. Obesity could lead to coronary heart disease, high blood pressure, diabetes, and hypertension, while being overweight contributes to depression and high blood pressure.

A survey conducted by National Institute of Diabetes and Digestive and Kidney Diseases indicates that prevalence of obesity is similar for both men and women, but about 8 percent of women are considered to have extreme obesity, compared to 4 percent in men.

Among young people aged between two and nine, about 18.6 percent of boys and 15 percent of girls are considered to be obese.

A study conducted of all 50 states by personal finance company WalletHub analyzed in 2016 determined the nation’s fattest states.

Mississippi took the number one spot, followed closely by Louisiana, Arkansas, Kentucky and Tennessee. Mississippi was found to have the highest rates of physically inactive adults, diabetic adults and adults with high blood pressure.

Read: What Causes Obesity? 10 Food Items That Can Cause Excessive Weight Gain

“Although this report didn’t delve into specifics, this typically means higher insurance premiums for everyone, not just obese or overweight individuals,” Jill Gonzalez, one of the study’s analysts, told the International Business Times at the time. “Future generations could experience shorter expected life spans if healthy eating and exercise are not promoted strongly.”

According to the State of Obesity, a project by the Trust for America’s Health and the Robert Wood Johnson Foundation, the costs of obesity range from $147 billion to $210 billion each year. The report said, "obese adults spend 42 percent more on direct healthcare costs than adults who are a healthy weight."

"Reducing obesity, improving nutrition and increasing activity can help lower costs through fewer doctor's office visits, tests, prescription drugs, sick days, emergency room visits and admissions to the hospital and lower the risk for a wide range of diseases," the report added.