Fasting – is it worth it?



Why Do this to Myself?

I have been wanting to try a fast for many years. Pregnancy or nursing had postponed this experience for me until recently. Before starting my fast, I considered how I might respond. There is the mental challenge and the curiosity about how I will handle it. There is the physical challenge of resisting the body’s screaming urge to eat. And why do this to myself? Well, for science. Or rather, because of science.

Fasting for Science!

Evidence from studies on mice and also on humans show that fasting decreases IGF-1 levels in the body. IGF-1 is a hormone (Insulin-like Growth Factor – 1) that signals the body’s cells to divide at a faster rate. When we are children and growing, this is the driving force behind our body’s cell division. But when our bodies are done growing, we no longer need high levels of IGF-1 and in can instead, cause increased cell division and increase our chances of cancer. Additionally, when the body is in “go-go” mode, making large amounts of IGF-1, it doesn’t take the time to search out defective cells and get ride of them in the body.

Studies have confirmed that fasting lowers the body’s production of IGF-1 and signals the body to go into “repair mode”, searching out defective DNA and destroying it. Although none of the studies looked at how people responded if they ate animal products or were vegan. A vegan diet also lowers IGF-1 dramatically, so it isn’t clear if there is a marked benefit for vegans to fast when they are already decreasing IGF-1 through their lifestyle.

There are many suggestions on how to fast and how often. The evidence points to fasting for a length of 5 days with around 500 calories per day. This fast period can be repeated 4 times a year (every 3 months) to help increase a person’s lifespan and health span. Mice who fasted in this way increased their life and health-span by 40%. Not only did they live longer, but they had no ailments in their old age.

Another part of this puzzle of avoiding cancer and other western diseases like heart disease and diabetes, is to decrease your IGF-1 on a daily basis. The most consistent way of increasing IGF-1 is to consume animal products. By eating vegan, the body’s production of IGF-1 decreases, significantly lowering the risk for cancer, heart disease, and diabetes.

This Isn’t For Me

I chose to do a coconut water fast, which ended up being about 600 calories of coconut water a day. After trying the fast for 3 days, I ended it early. I found the fast to be defeating many of the healthy lifestyle choices I had made for myself. For one, the fast made me tired during the day, to the point of needing a nap, and then unable to feel sleepy at night. I would be up until midnight or 1am, when normally, I am super tired if I stay awake past 10:30. Normally I sleep 8-10 hrs a night, but during the fast, I would wake up feeling tired yet unable to sleep in. I have recently been getting more sleep routinely, which has been helping me to lose and maintain my weight better. Fasting just messed up my natural sleep rhythms.

As a mother of two small children, I was in the kitchen frequently helping them with meals and snacks. Doing this while fasting was driving me crazy. If I were to do a fast again, I would only do it in a situation where I wasn’t handling other people’s food all day. Also, by the second day forward, I found myself becoming very short with my kids, something that I wasn’t happy with. Perhaps when they are older and are making their own food I will try again. And next time, it would be much easier to fast on water instead of teasing my body with a small amount of calories each day.

The side effects of my fast were fatigue, irritability, changes in sleep patterns, lack of creativity (brain power), and some weight loss around the waistline. Oddly enough, I began to have lower back pain on the 2nd day, which wasn’t exercise induced and isn’t normal for me. I found it difficult to keep pace with my children’s energy level, and my patience was short.


Because I have a very sensitive metabolism, fasting is probably not a good choice for me, as it changes the metabolism of the body drastically in a short period of time so that the body switches into ketosis and burns it’s own fat for fuel.

I also began to wonder what the benefit could be of lowering my IGF-1 levels with a fast, given that I eat a vegan diet, which already lowers my IGF-1 levels significantly. Dr. Gregor agrees with this idea, and doesn’t recommending fasting for vegans. All of the participants in studies of fasting and IGF-1 levels have been meat eaters, so there is no real evidence if there is an additional benefit for vegans to participate in lowering IGF-1 through fasting. For a meat eater, there many be significant benefits to fasting in order to increase one’s longevity and health-span. But if a person were this concerned about being healthy and living longer, eating vegan is a more proven and viable solution to fasting.



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