Adam’s Journal
Here’s a question from one of our Oklahoma Medical Research Foundation colleagues:
One of my friends recently told me they had been fasting for four days, water only, and had read about the many health benefits of long-term fasting for resetting your body. Are there health benefits for this kind of fast? And if there are benefits, do they outweigh the risks?
Misty Mihelich
Dr. Scofield Prescribes
People have for many years been interested in the health benefits of fasting, and in recent years that interest has increasingly turned to prolonged fasting.
Generally, prolonged fasting involves eating little to no food (or caloric beverages) for several days to weeks. The main types are: (1) water only, which is what it sounds like and what our questioner’s friend was apparently doing; and (2) what’s known as Buchinger fasting, where a person takes in about 200-300 calories a day in soups and fruit and vegetable juices.
A review of studies of prolonged fasting shows that the practice does, indeed, have some short-term health benefits.
Not surprisingly, prolonged fasting lasting 5-20 days almost always yields weight loss, typically 2-10%. It also leads to a consistent decrease in blood pressure, both systolic (when the heart beats) and diastolic (when it’s at rest).
Some studies have shown a decrease in low-density lipoprotein (LDL or “bad”) cholesterol and triglycerides, while others showed no benefit.
In non-diabetic adults, prolonged fasting yielded positive results for glycemic control, including reductions in levels of blood glucose, insulin and insulin resistance. But people with diabetes did not experience any of these metabolic benefits.
While not particularly enjoyable – no one likes being hungry, especially not for days or even weeks on end – prolonged fasting is relatively safe. The adverse events most commonly reported were headaches, insomnia, fatigue and dizziness.
That’s the good news on prolonged fasting. Now the less good.
When studies stepped back from the short-term effects of prolonged fasting and looked at the state of affairs 3-4 months later, it turned out that the nearly all the beneficial effects had vanished.
Metabolic indicators, blood pressure and cholesterol had all returned to pre-fasting levels. This was true even in individuals who’d managed to maintain weight loss, which some did.
So, prolonged fasting appears to be a generally safe diet therapy that can produce weight loss in the short- and even long-term. However, at least at this time, there’s little evidence it leads to sustained cardiovascular or metabolic improvements.
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Dr. Hal Scofield is a physician-scientist at the Oklahoma Medical Research Foundation, and he also serves as Associate Chief of Staff for Research at the Oklahoma City VA Medical Center. Adam Cohen is OMRF’s senior vice president and general counsel. Send your health questions to contact@omrf.org.
