Chapter 57
Obesity and Diabetes — 16
Metabolic syndrome and prediabetes are two overlapping but different conditions, and both predict increased risk of type 2 diabetes. Even if diabetes doesn’t manifest, they both can lead to cardiovascular disease and premature death. As seen in the table below for metabolic syndrome, and similar to the profile of prediabetes, neither is simply about how much one weighs; a substantial proportion of the people at risk are not obese.
The diagnosis of prediabetes is purely based on glucose metrics: either a fasting blood glucose of 100 to 125 mg/dL or Hemoglobin A1c between 5.7 and 6.4 percent. Diabetes is diagnosed by a fasting glucose of 126 mg/dL or higher, a random blood glucose greater than 200 mg/dL, or Hemoglobin A1c more than 6.4 percent. Normal is below 100 mg/dL fasting glucose and less than 5.7 percent Hemoglobin A1c. According to the Centers for Disease Control and Prevention, about one hundred million Americans have prediabetes. The higher the Hemoglobin A1c, the more risk of heart disease.
On the other hand, the diagnosis of metabolic syndrome relies on at least three of the five conditions of the cluster to be present, as reviewed earlier (high blood pressure, high fasting blood glucose of 100 mg/dL, abnormal waist circumference, low HDL, and high triglycerides), only one criterion overlaps with prediabetes. Accordingly, a significant proportion of people diagnosed with metabolic syndrome may not have the abnormal fasting blood glucose. Ironically, however, the number of Americans who have metabolic syndrome is also about 100 million, as calculated from the 2020 National Health and Nutrition Examination Survey data, with an adult population of 255 million people. Note in the table below that the 100 million adults with metabolic syndrome are almost equally divided between obese and nonobese.
Category
Number of Americans (in millions)
Obese with metabolic syndrome
50.9
Obese without metabolic syndrome
31.8
Nonobese with metabolic syndrome
49.1
Nonobese without metabolic syndrome
123.4
(Adapted from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6484904/
https://www.cdc.gov/nchs/about/factsheets/factsheet_nhanes.htm
https://academic.oup.com/pmj/article/99/1175/985/7076129)
Counter to what many would anticipate, the highest risk of death among people with metabolic syndrome is not in the people who are obese; it’s those with normal weight and overweight, as seen in a Centers for Disease Control and Prevention three-year follow-up study. While those with normal weight had the highest mortality, people who were obese carried substantially more risk than those who didn’t have metabolic syndrome at all (fig. 4.4). Not all studies agree with this observation of highest risk in those with normal weight, but it has raised awareness for the importance of diagnosing metabolic syndrome in people irrespective of their body weight, highlighting that factors not related to body weight (such as waist circumference) are critical components of the diagnosis.