Metabolic syndrome is what researchers call the cluster of risk factors that increase a person’s risk of other health conditions, particularly diabetes, coronary heart disease, and stroke. Within this “cluster” are glucose intolerance, hypertension, dyslipidemia, and obesity.
For people diagnosed with this syndrome, making lifestyle changes may seem daunting. However, intermittent fasting (IF), where a person doesn’t eat or drink for a period of time, typically ranging from 12 to 16 hours, may be the quickest start to pivot back toward greater health.
According to a study in the journal Obesity, IF had a favorable impact on all the risk factors of metabolic syndrome in mice, as well as decreased visceral fat, and contributed to overall weight loss.
The researchers believe that the mechanism responsible in IF for improving metabolic risk factors is one they call “flipping the metabolic switch.” This means shifting the body out of its habitual mode of burning glucose (a process called glycogenolysis) to burning fatty acids and ketones (ketosis).
The metabolic switch typically takes place in a later phase of fasting, when the glycogen stores contained in the liver are depleted and adipose tissue (fat) begins to increase fatty acids and glycerol. While the switch generally occurs between 12 and 36 hours after stopping eating, it can depend upon the total liver glycogen content when the person started the fast, as well as the person’s energy expenditures during the fast.
The lipids (fats) are metabolized to fatty acids that are released into the blood. At the same time, other cells may also produce ketones, including cells known as astrocytes in the brain. This switch, the authors say, essentially represents a shift from the body synthesizing and storing fat, to mobilizing fat in the form of free fatty acids (FFAs) and fatty acid‐derived ketones. They suggest that this process may have potential in treating obesity, diabetes, and metabolic syndrome.
However, there are some caveats, including the limited number of studies on fasting in humans and the fact that most of the rodent studies are done on male mice. According to a study in the Annual Review of Nutrition, time-restricted fasting (of which IF is one type) should also be synchronized with an individual’s circadian rhythms in order to be effective. Rodents who were fed a high-fat diet during the night, which disrupted their normal nocturnal feeding cycle, became obese and metabolically dysfunctional, the authors report.
Additionally, for people with diabetes who take insulin or sulfonylurea drugs to maintain their blood glucose, intermittent fasting poses some risks. It has been shown to raise the risk of low blood glucose unless appropriate adjustments are made, and should only be undertaken with the oversight of a medical professional. Additionally, If may not be right for people who are pregnant, under age 20, or underweight, or who take medications such as beta-blockers.
For those without high risk factors, IF is a good starting point to improve health, but anyone interested should consult their doctor first.