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Obesity definition

Obesity definition is well known – the obesity is an excess proportion of total body fat. In general the obesity occurs when a person consumes more calories than they need for the energy they use. In general a woman is considered obese when her weight is 20% or more above normal weight.
Body weight depends on a balance between the energy you get from food/drinks and the energy you spend. Every day the body use energy in following ways:

  • Energy expended during relaxation/rest (basal metabolism);
  • Energy used to break down food and different types of drinks (thermogenesis); and
  • Energy used during physical activity

Obesity definition – Body energy balance

Basal metabolism accounts for about two-thirds of spent energy. Your body generally uses this energy to keep your temperature steady and the muscles of your heart and intestine working. Thermogenesis accounts for about 10% of spent energy.
When a person consumes more calories than the energy they use, the body stores the extra calories in fat cells (lipocytes). Fat cells function as energy reservoirs. They grow or shrink depending on how people use energy. If you are not able to balance energy input and output by eating/drinking correctly and exercising adequately, fat can build up. This can lead to weight gain and obesity.

Obesity definition – Fat and Obesity

Obesity definition – obesity measurements

Many people just check their weight but obesity is determined by measuring body fat, not just body weight. People might be over the weight limit for normal standards, but if they are very muscular with low body fat, they are not obese. Others might be at normal weight or even underweight, but still have excessive body fat.

It is very important to know how correctly the weight, fat and obesity should be measured. It is important to preventing health risks which are correlated with extra weight and fat. The following measurements are used to determine whether or not a person is overweight and/or obese:

  • Body mass index (BMI),
  • Waist circumference (size around the waist),
  • Waist-hip ratio,
  • Skin fold measurement (anthropometry).

Obesity definition – The Body Mass Index (BMI)

The Body Mass Index is considered the most common measurement for identifying the obesity and the stage of obesity. Body Mass Index (BMI) is usually used for objective obesity measures. Women could be considered overweight if their BMI is between 25 and 29.9 and women could be considered obese if their BMI is over 30.

BMI formula

Obesity is classified into three categories:

Class 1 – BMI of 30 – 34.9

Class II – BMI 35 – 39.9

Class III – BMI of 40 and greater

These guidelines are very important for people at risk for diabetes, heart disease, or certain cancers. It is also used to determine treatment approaches such as when surgery may be appropriate. The higher the BMI = the greater is the risk for significant health problems.

Obesity definition – Waist Circumference and Waist-Hip Ratio

The extent of abdominal fat can also be used in assessing risk of disease. Some studies suggest that:

  • Women whose waistlines are over 31.5 inches and men whose waists measure over 37 inches should watch their weight.
  • A waist size greater than 35 inches in women and 40 inches in men is associated with a higher risk for heart disease, diabetes, and impaired health.

Evidence strongly suggests that more body fat around the abdomen and hips (the apple-shape) is a more consistent predictor of heart problems and health risks than BMI.

The distribution of fat can be evaluated by dividing waist size by hip size. For example, a woman with a 37-inch waist and 43-inch hip circumference would have a ratio of 0.86; one with a 42-inch waist and 40-inch hips would have a ratio of 1.05. The lower the ratio = the better. The risk of heart disease rises sharply for women with ratios above 0.8 and for men with ratios above 1.0.


The higher the ratio = the higher is the risk of heart disease and other obesity-related disorders.

Anthropometry – Skin-Fold Measurements

Skin-Fold Measurements

Anthropometry is the measurement of skin fold thickness in different areas, particularly around the triceps, shoulder blades, and hips. This measurement is useful in determining how much weight is due to muscle or fat. The skin-fold measurement test is one common method of determining a person’s body composition and body fat percentage.

Skin-fold test estimates the percentage of body fat by measuring skin-fold thickness at specific locations on the body. The thickness of these folds is a measure of the fat under the skin, also called subcutaneous adipose tissue. Skin-fold thickness results rely on formulas that convert these numbers into an estimate of a person’s percentage of body fat according to a person’s age and gender.

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