Metabolic syndrome (MetS) is a medical term for a constellation of health symptoms or markers related to insulin resistance in the body.
It is also called Syndrome X, a term coined by Gerald Reaven, the researcher who first identified and described the MetS condition. Having MetS indicates an increase in the risk of developing diabetes, cardiovascular disease and other health disturbances.
Insulin resistance is a condition in which chronically high levels of blood sugar and insulin have caused the body’s mechanism for regulating insulin and blood glucose (sugar) to fail. If left untreated, being insulin resistant usually leads to MetS, prediabetes and possibly a diagnosis of type 2 diabetes (T2D).
In fact, I believe that people who are diagnosed with type 2 diabetes had insulin resistance which progressed over time to MetS and prediabetes before they were given a final diagnosis of T2D. If someone has MetS, it's a warning sign that more serious metabolic conditions can develop in the future in a linear fashion:
The diagnosis of MetS is done by looking at a specific set of health parameters. A person can be diagnosed with MetS or "Syndrome X" if three out of the five following health characteristics is present in his medical examination:
Some people may have all of these symptoms, others may exhibit just three, but all of these health symptoms are individually associated with the development of prediabetes, Type 2 diabetes and heart disease.
In a research paper by Jeff Volek and Richard Feinman, MetS is defined as a condition of "intolerance to carbohydrate." They also state that "Although there is no universally accepted definition or mechanism, a rough common denominator is the set of five features: obesity (high body weight, BMI and/or waist circumference), high glucose and insulin levels, low HDL, high TAG and high blood pressure. Involvement of insulin resistance is generally a common feature and a likely causative agent for at least some of the symptoms.A subset of these metabolic markers, the TAG:HDL ratio, has been proposed as a simple marker for identifying insulin resistance."
The TAG:HDL ratio refers to comparing the levels of blood triglycerides to HDL cholesterol measurements.
Not surprisingly, the most effective treatment for MetS is a ketogenic diet. The goal is to reduce the insulin resistance which is at the root of MetS, and a ketogenic diet is specifically designed to do this. In this study, the researchers discussed the large body of evidence showing that a low carbohydrate diet reverses all of the diagnostic factors associated with MetS.
Other trials have shown that ketogenic diets are more effective than low fat diets AND more effective than low glycemic diets. And this meta analysis review confirmed that low carb diets are effective in treating MetS.