Can Obesity Be Diagnosed?
As part of any evaluation of obesity, first other causes (besides improper diet) should be ruled out, such as a neuroendocrine cause, e.g., hypothalamic obesity and hypothyroidism. When obesity is felt to be due to dietary excess, explorations into eating frequency, overeating with large portions, and high fat diets are considered. Finally, psychological causes are considered, such as depression, anxiety, or a history of abuse.
Obesity refers to excess fat, but there isn’t a way to directly measure someone’s actual fat content. The current standard is to compute a “body mass index” (BMI), which is the relationship between height and weight.
BMI as kg/m2 = body weight (kg) ÷ [height (m)]2
The result is plotted against a BMI template in which there are assignments that range from underweight to severely obese. Children must be adjusted for advancing growth, but for adults, a BMI of:
- < 18.5 kg/m2 : UNDERWEIGHT.
- 18.5 -24.9 kg/m2: NORMAL.
- 25-30 kg/m2: OVERWEIGHT.
- ≥ 30 kg/m2: OBESE; ≥ 35 kg/m2: SEVERE OBESITY (Class II); ≥ 40 kg/m2: SEVERE OBESITY (Class III)
Waist circumference is also part of the evaluation of obesity, especially as it relates to the abdominal obesity consistent with the metabolic syndrome and its association with insulin resistance.
- A circumference of ≥40 inches for men or ≥ 35 inches or women is considered abnormal and increases cardiovascular risk.
Other Testing Indicated with Obesity Includes the Following:
- Fasting blood sugar, oral glucose tolerance test, or hemoglobin A1c, as part of diabetic management or screening
- Lipid panel
- Appropriate cardiovascular testing
- Thyroid function tests (TSH initially) to rule out an endocrine cause of obesity, such as hypothyroidism
- In women, evaluation of menstrual cycles (specifically, ovulation) and serum testosterone and other hormonal levels are necessary to rule out Polycystic Ovarian Syndrome (PCOS), a gynecological endocrine disorder that causes weight gain and virilization due to elevated testosterone