Waist circumference

November, 2014

Miguel Murguía-Romero y J. Rafael Jiménez-Flores

There are several ways to assess a person's correct weight, one of which is waist circumference, which is measured at the level of the navel. For young Mexicans, we have adopted values of 80 cm or greater in women and 90 cm or greater in men as indicating abnormal weight, that is, central obesity.

There are several ways to assess a person's proper weight, one of which is waist circumference, measured at the level of the navel. For young Mexicans, we have adopted that values of 80 cm or greater in women, and 90 cm or greater in men, indicate an abnormality, i.e., central obesity.

It is complex and difficult to determine with a single measurement whether a person has an adequate weight or not, so it is advisable to use other criteria such as the body mass index, the waist-to-hip ratio, or even considering waist circumference at different times of day.

The body mass index is calculated by dividing weight (in kilograms) by the square of height (in meters). Generally speaking, values between 18.5 and 25 correspond to an adequate weight, while values below 18.5 correspond to thinness, and values above 25 to overweight.

The waist-to-hip ratio is calculated by dividing the length of the former (measured at the navel) by the length of the latter (measured at the height of the buttocks and pubis). In general, a value equal to or greater than 0.85 in women, and equal to or greater than 0.90 in men, indicates abnormalities, meaning it is recommended that our hips be larger than our waist, regardless of whether we are women or men.

Among the participants in the latest evaluation, at the end of 2013, of the "Health in Young University Students" project at UNAM's Iztacala School of Social Work (FES Iztacala), 41% of the students had abnormal waist circumferences. Analyzed separately, 49% of women had abnormal waist circumferences, meaning their waists measured 80 cm or more, and 27% of men had waists equal to or greater than 90 cm.

The graph shows the average HDL cholesterol, or "good cholesterol," separating students with and without abnormal waist circumference. It can be seen that for both women and men, the average is lower in the group of students with abnormal waist circumference values. The vertical bars represent the standard deviation. We performed the Student t-test, and the differences between the averages are statistically significant, for both men and women.
What do you think is the cause and effect? That is, it can be argued that having an abnormal waist circumference causes blood levels of HDL cholesterol to decrease, but the logical equation can also be changed and proposed that if our blood HDL cholesterol levels are low, then we tend toward central obesity.

Which do you think is the correct statement?