Thursday 1 March 2012

What is obesity?

Obesity is excessive accumulation of fat in the body to such a degree that it increases the risk of adverse health events. Obesity is not just a few extra pounds or kilos. However, excessive fat deposition invariably leads to increased body weight.

There is no universal definition for obesity and overweight. People use many different parameters to define these conditions. The commonly accepted system uses body mass index (BMI) as the sole criterion.

Definition of obesity

People with a body mass index of 30 or more are considered to be obese. A BMI of between 25 and 29.9 is called overweight.

Other definitions that are used to explain obesity and overweight:

  • A body weight that is greater than what is generally considered healthy for a given height.
  • Excess body fat accumulated to the extent that it may have adverse effect on health.
  • More than average fatness.
  • Obesity is defined as abnormal accumulation of body fat, usually20 per cent or more over an individual's ideal body weight.
  • Abnormal or excessive fat accumulation that may impair health.
  • Increased body weight caused by excessive accumulation of fat.
  • Excessive storage of fat in the body.
  • Obesity is defined as a medical condition of weighing at least 20 per cent over ideal body weight.
  • A condition in which excess fat is accumulated in the body, which is usually caused by the consumption of more food than is required for producing enough energy for daily activities.
  • Obesity is defined as gaining of excessive fat in the body to such a degree that it increases the risk of adverse health events.
Our body gets energy from foods that we eat everyday. When energy intake equals energy expenditure, the body is in energy balance. This means that your weight remains same. When you eat more than your body needs, the extra energy is stored as fat, and your weight is increased.

Energy from food is measured in calories or Joules.

1 food calorie ("Calorie") = 1 kilo calorie (kcal)
1 kilo-calorie = 4.2 kilo joule (kj)

About 7500 kcal energy is equal to 1kg of body weight. That means if you eat 7500 more Calories than needed, you will gain 1 kg of body weight.

The easiest and probably most accurate method of measuring obesity is the Body Mass Index (BMI).

                    weight (kg)
     BMI   =  ------------------
                    height (m) x height (m)

For example; if your weight is 100kg and height is 2m, then your Body Mass Index is 25.

--------- = 25
2 x 2

Classification of overweight and obesity.

BMI                       Grading

less than 18.5        underweight
18.5 - 25               healthy weight
25 - 30                  overweight
30 - 35                  grade 1 obesity
35 - 40                  grade 2 obesity
more than 40         grade 3 or morbid obesity

In addition to the amount, the distribution of body fat is also an important factor. For example; abdominal obesity possess more risk.

Waist circumference, waist-hip circumference ratio, and skin fold thickness are other important measurements that are used in the assessment of body fat percentage and distribution. Compared with BMI, the waist-hip ratio is a better predictor of cardiovascular risk.

Obesity is a complex medical condition caused by several factors. It is obvious that energy imbalance is the commonest cause. It means consuming too many calories or burning fewer calories. This article explains the leading causes of too much weight gain.

What causes obesity?

Eating too much

Consumption of extra calories is among the major causes of obesity.

Different foods contain different amounts of calories. When the total intake of calories exceeds the requirement, it causes excess weight gain. For example; if your daily energy need is 2000 kcal and you eat 2800 kcal a day, you will gain 100 g of body weight each day. That means 3kg in one month.

The amount of food that you eat is less important. Actually the type and calorie content of food matters. Fatty foods contain more calories than other foods. Similarly sweets have high energy content.

Lack of physical activity

Energy is needed for our physical activities such as walking, running, and gardening. Active people burn more fat for their energy needs. If you are less active, more fat will be deposited in your body and you will become overweight or obese. The energy imbalance is a major cause for obesity in people who live a sedentary life.

Genetic factors

Genes play significant role in the development of obesity. Genes are molecules found inside our body cells that carry important biological data from parents to offspring. Does it sound complicated? I will explain it simply. If your parents are obese, there is more chance that you get obesity.

The scientific evidence for genes as a cause for obesity comes from various studies. These investigations suggest that a significant percentage of excessive weight gain is due to genetic factors.


Chronic depression can be a cause for overweight. Depressed people are usually less active. The mental illness can make them less interested in outdoor activity. In addition, the medications used in the treatment of depression can cause tiredness and sleepiness.

Furthermore, people suffering from depressive illness tend to eat more to relieve their feelings. They are easily put on weight for these reasons.


Thyroxine; a hormone secreted by the thyroid gland regulates our metabolic activity. Under-activity of the thyroid gland is called hypothyroidism. Elevated levels of thyroxine hormone causes high metabolic rate. That means, people with high levels of thyroxine burn more calories,even at rest.

Conversely, people with reduced thyroid function have low metabolic rates. They burn fewer calories, and easily put on weight.

Cushing's syndrome

It is a disorder that causes increased production of steroid hormones by the adrenal glands. The excess of cortisol in the body slows down the metabolic functions. This leads to accumulation of excessive fat in the body.

The fat deposition mainly occurs in the abdomen and chest. This type of fat distribution causes central obesity.

Poly cystic ovary syndrome (PCOS)

This condition affects women in their reproductive age. There is an imbalance between female sex hormones, which include oestrogen and progesterone.

Experts still are not certain how PCOS causes obesity. However, it is obvious that many women with poly cystic ovary syndrome are overweight, even if they eat healthy diet and do exercise regularly.

Lack of sleep

Researches have shown that sleep deprivation can be a cause of obesity. Inadequate sleeping time and poor quality of sleep causes an imbalance between two hormones that regulate appetite. Lack of sleep results in elevated levels of ghrelin which increases our appetite.

Furthermore, sleep deprivation reduces the level of appetite suppressing hormone leptin. The end results is more eating and more weight gain.

Health risks of obesity

  • High blood pressure (hypertension)
  • Coronary heart disease (angina, heart attack)
  • Congestive heart failure
  • Type 2 diabetes
  • The metabolic syndrome
  • Stroke and mini strokes (transient ischemic attacks)
  • Obstructive sleep apnea
  • Cancer of the breast and uterus
  • Pulmonary embolism
  • Varicose veins (spider veins)
  • Cor-pulmonale
  • Increased cholesterol and triglyceride levels in the blood
  • Polycystic ovary syndrome (PCOS)
  • Gastro-esopageal reflux disease (acid reflux)
  • Sub-fertility
  • Obesity related fatty liver (fat accumulation in the liver)
  • Gallstones
  • Cancer of the colon (bowel cancer)
  • Hernias
  • Urinary stress incontinence 
  • Kidney dysfunction
  • Obesity related pregnancy complications
  • Testicular atrophy in males
  • Low back pain
  • Osteoarthritis of the knee and hip joints
  • Idiopathic intra-cranial  hypertension
  • Nerve compression syndromes (carpal tunnel syndrome, meralgia paresthetica)
  • Difficulty in breathing
  • Hypo ventilation syndrome
  • Asthma
  • Increased risk of developing depression
  • Low self esteem
  • Body image disturbance
  • Stretch marks on the skin
  • Discolouration and pigmentation of the legs
  • Skin tags
  • Swelling of legs
  • Superficial infections such as cellulitis
  • Increased risks of immobility and hospitalization
Obesity is linked with some of the most common medical problems that include physical as well as psychological complications.

Some of the obesity related health risks such as heart attack and stroke are potentially life threatening ones. So keep your body weight with in healthy range.

Related post.

Obesity in children.