Obesity is one of the biggest causes for preventable illness and death in many parts of the world. People who are obese are having increased risk of having serious medical conditions such as gallbladder disease, diabetes, stroke, heart attack, high blood pressure and different types of cancers. The term “obese” is used to describe a person who is very overweight and who have a lot of body fat.  This is one of the most common problems in UK and USA. There are many ways in which the health of the individual in relation to their weight can be classified but the method which is most widely used is BMI (body mass index). Body mass index is a measure of whether you are healthy weight for our height. For most adults a body mass index of:
- 5 to 24.9 means that these adults have a healthy weight
- 25 to 29.9 means that these adults are overweight
- 30 to 39.9 means that these adults are obese
- 40 or above means that these adults are severely obese
The body mass index is not used to definitively diagnose obesity because people who are very muscular sometimes have a high body mass index without excess fat. But for the most people, the body mass index is a useful indication of whether they are healthy, overweight or obese. 
Causes of obesity
The general cause for obesity is when you consume more calories, particularly those calories which are in sugary and fatty foods, than you burn off physical activity. In this case the excess energy is stored by our bodies as fat. This is one of the most common problems which is increasing as years are passing because we know that in this modern era many people are spending a lot of time sitting in cars, on sofas, at desks or sitting down and they eat excessive amounts of cheap and high – calorie food.  But also there are some underlying health conditions which in some cases can lead to weight gain such as hypothyroidism (which is an underactive thyroid gland), although these types of diseases or conditions do not usually cause weight problems if they are effectively controlled with medication. Here are the most common causes for obesity:
- Medical reasons: There are some cases in which underlying medical conditions can lead to weight gain and they include:
- Cushing’s syndrome: This is a rare disorder which can cause the over – production of steroid hormones 
- An underactive thyroid gland (hypothyroidism): This is a condition when your thyroid gland does not produce enough hormones 
- Poor diet: Obesity is not happening overnight. It develops gradually over time as a result of lifestyle choices and poor diet such as 
- Comfort eating
- Drinking too much sugary drinks
- Eating larger portions than you need
- Eating out a lot
- Drinking too much alcohol
- Eating large amounts of processed or fast food
- Genetics: There are rare genetic conditions which can lead to obesity such as Prader – Willi syndrome but there is not a reason why they cannot lose weight. There are some genetic traits inherited from your parents, such as having a large appetite, may make losing your weight more difficult but it is not impossible. 
- Lack of physical activity: This is important factor which lead to obesity. Many people have jobs which are involving sitting at a desk for most of the day and they are not walking or cycling, instead they are in their cars. Also they want to watch TV or surf the next instead of doing some physical activity. When they are not active enough, then they do not use the energy which is provided by the food they consume and the extra energy they consume is stored by their bodies as fat. They need to do exercises for thirty minutes a day in a period of 5 days a week. 
Risk of obesity
It is very important for all people to take steps to tackle obesity because it not just leads to physical changes but also it can lead to many serious and potentially life – threatening conditions such as
- Stroke 
- Some types of cancer such as bowel cancer and breast cancer
- Coronary heart disease 
- Type 2 diabetes 
Obesity can also affect the quality of your life and it can lead to some psychological problems such as low self – esteem and depression.
 World Health Organization. Obesity and overweight. 2020. Retrieved from www.who.int/news-room/fact-sheets/detail/obesity-and-overweight
 Camacho S, Ruppel A. Is the calorie concept a real solution to the obesity epidemic? Global Health Action. 2017;10(1):1289650.
 Tiryakioglu O, Ugurlu S, Yalin S, et al. Screening for Cushing’s syndrome in obese patients. Clinics. 2010;65(1).
 Sanyal D, Raychaudhuri M. Hypothyroidism and obesity: An intriguing link. Indian Journal of Endocrinology and Metabolism. 2016;20(4):554–7.
 Rush EC, Yan MR. Evolution not revolution: Nutrition and obesity. Nutrients. 2017;9(5):519.
 Centers for Disease Control and Prevention. Genes and obesity. Retrieved from www.cdc.gov/genomics/resources/diseases/obesity/obesedit.htm
 Kim BY, Choi DH, Jung CH, et al. Obesity and physical activity.
Journal of Obesity & Metabolic Syndrome. 2017;26(1):15–22.
 Kernan WN, Inzucchi SE, Sawan C, et al. Obesity: A stubbornly obvious target for stroke prevention. Stroke. 2013;44(1):278-86.
 Akil L, Ahmad A. Relationships between obesity and cardiovascular diseases in four Southern States and Colorado. Journal of Health Care for the Poor and Underserved. 2011;22(4Suppl):61–72.
 Chobot A, Górowska‐Kowolik K, Sokołowska M, Jarosz‐Chobot P. Obesity and diabetes—Not only a simple link between two epidemics. Diabetes/Metabolism Research and Reviews. 2018;34(7):e3042.