To know if they are a healthy size, many people rely on the scale, weight and height charts, or mathematical formulas that calculate body mass index (BMI).
However, new research reveals that a tape measure more accurately predicts a person’s risk for many major health problems.
This is because the waist measurement indicates the amount of abdominal fat – fat that accumulates deep in the abdomen, around the intestines, liver and other internal organs.
Abdominal fat is linked to a very high risk of diabetes, heart disease, stroke, high blood pressure and abnormal cholesterol levels…, some types of cancers, such as breast and colorectal cancer… and dementia.

Having a lot of abdominal fat is more dangerous than being overweight or even obese.

In a 16-year study of 45,000 nurses, women with waists of 35 inches or more were much more likely to die prematurely than women with waists of less than 28 inches, even when their weight was within the normal range for their height.
Women with an intermediate waist circumference had a small to moderate increased risk. Reason…

1. Abdominal fat can be more metabolically active than other fats, releasing free fatty acids (products of fat cells circulating in the bloodstream) directly to the liver.
   This can lead to insulin resistance (the body’s inability to use insulin properly) and generalized inflammation, both of which significantly raise the risk of diabetes and heart disease.
2. Abdominal fat can be a sign of fat deposits in the liver and around the heart, which can damage the functioning of the organ.
3. After menopause, the tendency to accumulate abdominal fat increases as women produce less estrogens relative to androgens (male hormones).
   Androgens promote abdominal fat.

To measure

Surround the waist with a tape measure at the level of the navel (usually below the narrowest area of the abdomen).
The tape should be snug, but not constricting to the flesh.
For women of any height, a waist size of less than 30 inches (76 cm) is optimal….
From 30 inches (76 cm) to 35 inches (89 cm) indicates a moderately high health risk… …And greater than 35 inches (89 cm) indicates a high risk. To reduce abdominal fat

1. Lose weight. Often, the first fat to disappear is abdominal fat.
   Even a modest loss of 10% of initial weight confers great health benefits.
2. Reduce stress. Stress causes the adrenal glands to secrete the hormone cortisol, which promotes abdominal fat.
3. Do the right kind of exercise. You can’t get rid of belly fat with belly-targeted exercises like crunches.
   Instead, engage in aerobic activities such as brisk walking and racquet sports.
   Doing three hours a week of aerobic exercise can eliminate about 50% of the excess heart disease risk associated with abdominal fat.
   It can also eliminate up to 25% of the excess risk of diabetes.

Resistance exercises (such as exercising with weights for arms and legs) are also healthy.

References

https://www.nurseshealthstudy.org/

https://www.health.harvard.edu/staying-healthy/abdominal-fat-and-what-to-do-about-it

https://www.nytimes.com/2018/06/11/well/live/belly-fat-health-visceral-fat-waist-cancer.html