Fasting by the Hours - Timing and Benefits

Fasting is a great way to improve health in many ways, including weight loss, decreasing insulin resistance, treating diabetes, improving cardiovascular health, and turning over new healthy cells. There are many ways to fast, and I detail the how-to basic benefits in my previous blog. The gains from fasting can vary significantly depending on the length of the fast. It is helpful to evaluate goals before deciding what type of fast is best.

A 16-18 hour fast is the most common fast and probably the easiest and most convenient fast. In this fast, you would normally eat dinner and then fast overnight and either skip breakfast or have a late breakfast or even a late lunch. At this point, the body should have stopped producing insulin and growth hormone (HGH) levels begin to rise.  Higher levels of HGH tend to benefit body composition (more muscle and less fat), increase density of bones, and improve lipids.  In short, HGH promotes fat burning rather than fat storage. Also, because no food has been consumed, the body begins to break down fat for fuel instead of using glucose. This process usually produces ketones. These things usually don’t begin much before 16 or even 18 hours. The longer the fast extends, the greater the fat burning that occurs.

Doing one meal a day (OMAD) is also known as a 24 hour fast. In addition to the benefits seen with a 16-18 hour fast, the level of ketosis is generally deeper and that means that there is more fat burning. Another big benefit of fasting for 24 hours is that you begin to see autophagy at around 24 hours. Autophagy is the process of recycling in the body. Proteins are broken down and rebuilt. This gets rid of old damaged proteins and cells and new healthier ones are made. It can also remove toxins from the cells that can trigger neurodegenerative diseases like dementia or Parkinson’s disease. Autophagy can help to get rid of extra skin in people who have lost weight. It can be helpful for preventing cancer, improving metabolism, reducing inflammation, and improving muscle performance. Most importantly, it is believed that autophagy can slow the aging process.  This type of fast is often done a couple of days a week but could be done daily.

When fasting for 48 hours, people will continue to see autophagy. In addition, the insulin sensitivity will dramatically improve and peak around 48 -72 hours. The body is depleted of glycogen stores (this can be converted to glucose) and this keeps insulin secretion very low. Of course, fat burning continues. Growth hormone levels will get even higher and those benefits become magnified. Fat loss continues to improve. Energy levels rise. Hunger can be an issue but generally begins to subside after 48 hours.

A 72 hour fast will really ramp up the immune cell breakdown and rebuilding, hence improvement in aging, prevention of neurodegeneration seen with dementia etc, continue fat loss and peaks of growth hormone. While some people choose to fast for longer than 72 hours this should only be done with the help of a physician.

Many people feel like fasting causes muscle loss, but in fact that doesn’t seem to be the case with short fasts like the ones mentioned above. In fact, there is preferentially fat loss with preservation of muscle mass, thus making the body more metabolically active. This is certainly a good thing with regard to weight loss. When it is time to break your fast it matters what you eat as well. It is best to break a fast with a smaller meal of unprocessed foods including a good amount of fat and protein as well as some vegetables. It is best not to eat simple sugar and carbohydrates.

I think of fasting as a bonus to add to my regimen of healthy low carb eating. I do it when it feels good and when it is convenient. I tend to feel very mentally alert and full of energy when I fast. Admittedly, fasting is much easier when eating low carb because the body is already used to burning fat for fuel instead of glucose and the body easily switches right over.  Of course, if this is something you would like to try it is best to speak with your physician first. However, fasting is a great free and safe way to improve your health. Give it a try!