Last week, someone was preaching to me about the benefits of fasting. This particular person fasts for health and religious reasons, and told me they do it 2-3 (consecutive) days a week.
Of course, I was skeptical, especially after the person cited references to fasting testing done on worms. Sure, worms may live longer if they fast, but how long do they live anyway? And aren’t our digestive systems just a teeny bit different?!
The person preaching to me couldn’t give me any answers (of course), so I did a bit of research with my good buddy wikipedia, and am here to ask you your thoughts. Note, this is just about fasting for health reasons, not religious reasons.
What is fasting?
Fasting is the act of abstaining from all food and drink for a period of time. There are different types of fasts – certain ones allow water, raw food, or a very limited calorie intake. I am discussing a fast where you only drink water for a day or more.
What happens to your body when you fast?
Glucose is the body’s primary fuel source. When you fast for 4-8 hours, your body converts glycogen from your liver into glucose to use for fuel. Your body also uses protein to supplement the glycogen. This fuel will last for up to 12 hours, then your body will turn to muscle for glycogen. If glycogen is unavailable, the body will turn to fat as a fuel source. The body will continue to use fat until it is unavailable, at which point the body will switch to using protein for fuel, and will be in a state of starvation (fasts are normally broken before this point).
What are the benefits of fasting?
According to Dr. Mark P. Mattson*, fasting every other day (known as Intermittent Fasting) shows beneficial effects as strong as those in caloric-restriction diets (I would hope so…).
Other possible benefits:
- increased life span
- reduced risk of cancer, Alzheimer’s, cardiovascular diseases, diabetes, insulin resistance, and immune disorders
- stress resistance
- increased insulin sensitivity
- reduced morbidity
- detoxification – there is no evidence supporting this, and our bodies are naturally designed to remove toxins through our skin (sweating) and liver, colon and kidneys, but this is what the person was preaching to me
What are the dangers of fasting?
Intermittent fasting (eating every other day, typically) causes lowered blood sugar and blood pressure, which can lead to dizziness and blackouts. Oh yeah, and it makes you possibly feel weaker and CRANKY.
As you fast, your body lowers its metabolism to conserve energy; when you go back to your normal diet, your lowered metabolism may cause you to store more energy – a possibility of gaining weight.
If you fast for too long, your body will lack a variety of vitamins, minerals and nutrients, which can lead to symptoms such as fatigue, dizziness, constipation, dehydration, gallstones, and cold intolerance. Fasting for too long also causes your body to go into a starvation mode. From wikipedia: “Medical complications associated with fast-induced starvation include electrolyte imbalances, thinning hair, lanugo, cardiac arrhythmia and renal failure.” Also, what distinguishes fasting from essentially starving yourself? Is there a risk of it getting out of control?
Will I try fasting?
Probably not. As I told the person who was preaching this to me – I eat every 3-4 hours now, or I get a headache and feel unwell. They assured me that I could build up to fasting – similar to how I told them they could build up to running, slowly. But, I just don’t think this is something I need to get in to. As someone who prefers to participate in endurance activities and exercise regularly, I prefer to be “fueled.” (Although some say it is fine to exercise when fasting… not sure that is for me).
Sometimes, I do a lighter diet for a day, sort of a “detox” to get myself back on track. I guess that is the closest I will get to fasting.
What do you think about fasting? Have you ever tried it? Do you think it could be beneficial? Do you think it’s a load of crap?
Side Note #1: Don’t forget to enter my Love to Run Pendant Giveaway!
Side Note #2: If you voted yes to read my Training Week 17 poo story (18 out of 21 did!), it has been updated here.
*Chief of the laboratory of neurosciences at the National Institute on Aging