Overweight and obesity are known as an abnormal or increased fat accumulation that poses health risks. A Body mass index (BMI) is an index that measures weight-for-height and classifies obesity and overweight in adults. According to the World Health Organization (WHO) overweight is a BMI higher than or equal to 25 and obesity is a BMI higher than or equal to 30. An imbalanced energy between calories consumed and calories used is the main cause of obesity and overweight. Obesity has a combination of causes and factors contributing to it, including genetics, family lifestyle, physical inactivity, and unhealthy diet.

The pathophysiology of various disorders and diseases such as diabetes mellitus, hypertension, atherosclerosis, insulin resistance, dyslipidemia have major contribution from obesity. Some of the health issues that pose a daily problem in individuals include increased sweating, snoring, and several psychological problems such as depression.

BMI is measured for a child or an adult by the doctor in order to diagnose overweight and obesity. The cause and severity of the condition define the treatment for overweight and obesity. Possible treatments include adopting a healthier lifestyle that may include physical activity and having enough sleep, behavioral weight-loss programs, certain medications, and surgical procedures.

If gone untreated, obesity can increase the risk of developing life-threatening and serious conditions such as some forms of cancer, heart disease, stroke, high blood pressure, and type 2 diabetes. The lowest rates of obesity have been reported in Asia while the highest ones were in the Pacific Islands. Variation regarding obesity rates in Africa and Middle Eastern have been reported.

The abnormal or increased fat accumulation that poses a risk to health is known as being overweight and obese.  Obesity, a serious medical issue, leads to various complications such as high blood pressure, metabolic syndrome, atherosclerosis, heart disease, diabetes, cancers, sleep disorders, and high blood cholesterol.

Body mass index (BMI) is an index of weight-for-height for classifying obesity and overweight in adults. It is calculated as a person's weight in kilograms divided by the square of his height in meters (kg/m2). Age needs to be taken into consideration when calculating overweight and obesity for children.

Overweight and obesity in adults are defined by the World Health Organization (WHO) as (1):

• Overweight is a BMI higher than or equal to 25.
• Obesity is a BMI higher than or equal to 30.

Mainly, obesity and overweight are caused by an energy imbalance between the calories consumed and the calories used. Worldwide, the causes of obesity are (1):

• Increased intake of energy-dense foods that are rich in fat.
• Decreased physical activity due to the increasing need for many forms of works that require long hours of sitting,  changing modes of transportation, and increasing urbanization.

A combination of causes and factors contribute to obesity, which are:

• Genetics

 Genes define the quantity and location for fat storage and distribution, respectively.

• Family lifestyle

 The risk for obesity is increased for a child when one or both parents are obese. Obesity have been reported to run in families due to shared similar eating and activity habits.

• Inactivity

 Less activity leads to burning less calories and hence obesity.

• Unhealthy diet

 Diets that are high in calories, processed or fast food, and with no fruits or vegetables makes an individual gain weight more.

• Medical problems

 Medical conditions such as Prader-Willi syndrome and Cushing's syndrome can lead to obesity.

• Certain medications

Some antidepressants, antipsychotic medications, anti-seizure medications, steroids, beta blockers, and diabetes medications contribute to weight gain if not compensated through activity and diet.

• Social and economic issues

Economic factors affect obesity and overweight throughout not providing enough money to buy healthier foods or not finding safe areas to exercise or lacking the knowledge of cooking in a healthy way. Social factors include that the person who has obese friends or relative is more likely to become obese.

• Age

 Hormonal changes and living a less active lifestyle affect obesity throughout the aging process. However, obesity can occur regardless of age.

• Pregnancy

 The weight gained during pregnancy becomes harder to lose; post delivering according to many women.

• Quitting smoking

 Quitting smoking can often lead to weight gain.

• Lack of sleep

Having too much or not enough sleep causes hormonal changes that increase the appetite.

When normal adipose accumulates, obesity develops. Obesity secretes inflammatory adipokines, which trigger immune dysfunctions and form a major risk factor for various cancer types, such as colon, esophageal, and hepatocellular.

Obesity plays a major role in metabolic dysfunction that involves lipid and glucose, and on a broader scale, it contributes to organ dysfunction involving cardiac, liver, reproductive, intestinal, pulmonary, and endocrine functions.  Obesity plays a major role in the pathophysiology of various disorders and diseases including diabetes mellitus, hypertension, atherosclerosis, insulin resistance, and dyslipidemia.  

Obesity can lead to daily health issues such as:

• Increased sweating.
• Snoring and breathlessness.
• Inability to cope with sudden physical activity.
• Back and joint pain.
• Low confidence and self-esteem.
• Feeling very tired every day.
• Psychological problems such as depression and feeling isolated.

The healthcare provider might use one of the following methods to diagnose obesity:

• Confirming a high body mass index (BMI)

To confirm that a child or adult is obese, the doctor will calculate the BMI of the person and compare the results to a scale.  For adults, a BMI between 25 and 30 confirms overweight, whereas a BMI that exceeds 30 confirms obesity. In the case of children, age is an important factor, so the doctor will compare the BMI with growth charts for children who share the same age and sex to confirm the diagnosis. 

• Reviewing medical history

 The person suffering from obesity should be asked by the doctor about family history, eating and physical activity habits, and potential risk factors.  This is done in order to determine whether the cause of obesity is related to other conditions or if the patient is suffering from complications that are a result of being overweight or obese.

• Performing physical examination

A waist circumference over 40 inches for men and 35 inches for females who are not pregnant is an indicator for obesity.

• Recommending other tests

 These include blood tests and pelvic ultrasound that help rule out certain conditions, for example, thyroid hormone levels can help rule out hypothyroidism and examining ovaries detects cysts which rules out Poly Cystic Ovaries Syndrome (PCOS).

The treatment for overweight and obesity is governed by the cause and severity of the condition. Possible treatment option include:

• Adopting healthier lifestyle

 This may include an increased physical activity and maintaining a healthy diet, and having enough sleep.

• Behavioral weight-loss programs

 A customized weight-loss plan proposed by a trained healthcare professional will include physical activity goals, a moderately-reduced calorie diet, and behavioral strategies in order to make sure that healthier lifestyle changes are made and maintained.

• Medications

 Food and Drug Administration (FDA)-approved weight-loss medicines may help treat obesity. The urge to eat is regulated by the brain, which can be adjusted by several drugs that decrease the appetite. Some examples of these drugs are diethylpropion, phendimetrazine, lorcaserin, naltrexone/bupropion, and liraglutide.. Other drugs work on blocking the intestines from absorbing fat from foods in the diet, orlistat is the only available medicine in this category.

• Surgical procedures

1- Gastric bypass surgery

This can be done by connecting a small part of the stomach to the middle part of the intestine without going through the first part of the intestine which leads to a drop in food intake, and hence the body fat taken and stored.

2- Gastrectomy

In this procedure, a large amount of the stomach is removed which decreases the amount of food intake.

3- Surgery of gastric banding

Here, a smaller stomach is made by placing a hollow band around the upper part of the stomach which also decreases food intake.

Serious health issues related to obesity include:

• Type 2 diabetes.
• High blood pressure and heart disease.
• A combination of high blood sugar, high blood pressure, high triglycerides and low HDL cholesterol which makeup a metabolic syndrome.
• Cancer such as cancer of kidney, prostate, colon, rectum, uterus, cervix, endometrium, ovaries, breast, esophagus, liver, gallbladder, and pancreas.
• Breathing disorders such as sleep apnea.
• Gallbladder disease.
• Gynecological problems such as irregular periods in woman and infertility.
• Erectile dysfunction and other sexual health concerns in men.
• Nonalcoholic fatty liver disease.
• Osteoarthritis.
• Stroke.
• High triglycerides and low high-density lipoprotein (HDL) cholesterol.

When the case is a person with a BMI much closer to be considered overweight or even having certain risk factors, healthy lifestyle changes are recommended by the doctor to stop the case from advancing into overweight and obesity. The recommended changes may include healthy eating, getting enough amounts of sleep, and physical activities.

Life-threatening and serious conditions are more likely to develop with obesity and those include some forms of cancer, heart disease, stroke, high blood pressure, and type 2 diabetes.

 Several digestive diseases are caused by obesity such as gastroesophageal reflux disease (GERD) and its complications.

Pacific Islands are reported to have the highest rate of obesity.The lowest rates of obesity have been reported in Asia.

Generally, Europe and North American’s obesity rates are high, while a variation regarding obesity rates in Africa and Middle Eastern countries have been reported.

In Australia, over the past two decades, a doubling in the rates of overweight and obesity amongst adults has been seen, making Australia rank as one of the fattest developed nations in the globe.