One benefit of fasting is weight loss, but fasting does so much more! It's been practiced for hundreds of years, for religious and spiritual reasons - as well as to manipulate the body.
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Here are some of the concrete, physical benefits of fasting:
A benefit of fasting is that when you start, your blood glucose levels decrease. This happens because you're using up your blood glucose to fuel your body, which in turn causes your insulin levels to decrease.
Insulin is the primary hormone responsible for storing blood sugar as fat. Thus, when you have low blood sugar you start using fat as a fuel and insulin levels go down.
So you burn fat, and also re-familiarize your body with having a low insulin level. It boosts the insulin and weight loss connection.
This happens naturally when you sleep, since when you sleep you're in a fasted state. So, think of fat more as a short term battery than as a long-term, difficult to access storage warehouse.
Another benefit of fasting is that you're living off the stored energy and nutrients in your body when you fast. So, you're mostly living off your fat!
Since there're no new food, you have only what's left in your body. Fat will supply about 85% of the energy, and the protein of your muscles will be broken down slightly to supply about 15% of your energy, tops.
Another benefit of fasting is that it...
This is closely linked with the decrease in insulin levels during a fast. Having low levels of insulin gets your body used to using insulin efficiently.
You might think this is bad. If insulin works to put on fat when you eat, wouldn't making you more sensitive to it help you put on more fat?!?!?!? Actually, no.
If your body is more sensitive to insulin, then your body releases less of it to control your blood sugar - since a little goes a longer way. And less insulin release means less fat storage.
Insulin has lots of beneficial muscle building effects too, but the primary benefit of fasting on insulin is that it helps with weight loss.
Exercise in a fasted state really works to increase your insulin sensitivity. This boosts the benefits you get from fasting!
When you exercise in a fasted state, your burn up the glycogen (sugar) stored in your muscles and start to metabolize your fat for fuel. And your muscles want to be re-filled with glycogen after exercise - further increasing your short term insulin sensitivity.
Also, your exercise in a fasted state needs an energy source. And your fat is only too willing to oblige! The fat burning effect of fasted exercise is an awesome benefit of fasting!
Just keep in mind that if you're not used to exercising in a fasted state, it can be really draining. The first few times I did it I felt horrible - but I was fine once my body got used to using fat for fuel ;-)
This is useful on occasion to give your internal organs a rest, and re-adjust what your metabolism is doing. A longer fast, for around 48 hours, is sometimes used at the beginning of diets to break an established metabolic pattern of fat synthesis and accumulation.
Once in a while, mix things up with a fast. I think this is one of the best benefits of fasting - change up your eating to see what it's like to noteat!
This also simulates what our ancestors went through. Humans didn't have 3 nice, square meals a day, every day for the last several hundred thousand years.
So, try some changes to your eating and fast once in a while.
Another benefit of fasting is that it triggers an increase in growth hormone levels. In fact, fasting can boost your growth hormone to up to six times your normal levels!
Though for short periods of time, I hasten to add.
Growth hormone is released in increased quantities when you fast to maintain your lean muscle mass. That's why you get the majority of your energy when fasting from your fat, not through breaking down your muscle!
Growth hormone helps burn fat, build muscle, and increase your metabolism. All great if you're trying to burn fat and/or put on lean muscle mass!
But the biggest benefit of fasting is...
Yes, this is a concrete benefit of fasting. Until you decide to fast, or change your diet is some other way, you really don't consciously think a lot about what you're eating.
At least, I didn't. After all, it's just food ;-)
But fasting shows yourself how you use food. Do you find yourself wanting to eat when you're stressed? Or when you have particular friends around?
Fasting really gives you a new perspective on the position of food and eating in your life. That's what it did for me!
When you take a first taste of something, this triggers the release of your first wave of insulin for a meal. This wave packs away your fat (that you were using for fuel) and gets your body ready to start storing some of the food you're eating as fat. It also causes your hunger to increase!
So, when you're fasting don't cheat! It's not the amount of food that you're eating that will sabotage your fast, it's the change from not-eating to eating that deprives you of the benefits of fasting.
So, don't break your fast 'just a little.' Either do or do not - there is no try!
Fasting in fine short term. Intermittent fasting, fasting for a day or two, or anything like that can help you appreciate food and get the benefits of fasting.
But long-term fasting can (and probably will) negatively impact you. After 3 days, your metabolism starts to slow down, you begin to break down muscle tissue, and stuff goes bad from a benefit-the-body point of view.
To get hit with this adverse impact I'm not talking about fasting for 20 hours a day, then eating a big meal for weeks on end. I'm talking about not eating anything for 3, 4, or more than 5 days!
You can get any benefit of fasting by not eating for 1 - 2 days, and many times for less time. So, keep you fasts short and to the point!
The main things to take away from this are that...
And just remember, it's fine to drink water while fasting.
It might not be comfortable, but used once in a while (or for doing intermittent fasting) it's fine. Try it!
Oh, and be sure to sign up for the e-zine Starting Strong to get monthly strength training, exercise, and diet tips e-mailed to you - and access to the free e-book Train Smart, Eat Smart: Exercise Nutrition Hacks!
Any Benefit of Fasting? 6 Awesome Reasons To Try It!
1. Taubes, Gary. 2008. Good Calories, Bad Calories: Fats, Carbs, And The Controversial Science of Diet And Health. New York: Anchor Books. Pp. 425.
2. Taubes. Pp. 432.
3. Taubes. Pp. 385.
4. De Vany, Arthur. 2011. The New Evolution Diet: What Our Paleolithic Ancestors Can Teach Us About Weight Loss, Fitness, and Aging. Emmaus, Pa: Rodale. Pp. 53.
5. Karen Van Proeyen, Karolina Szlufcik, Henri Nielens, Koen Pelgrim,Louise Deldicque, Matthijs Hesselink, Paul P Van Veldhoven, and Peter Hespel. "Training In The Fasted State Improves Glucose Tolerance During Fat-Rich Diet". J Physiol September 13, 2010 jphysiol.2010.196493; published ahead of print September 13, 2010, doi:10.1113/jphysiol.2010.196493.
6. Taubes. Pp.412.
7. Pilon, Brad. 2010. Eat Stop Eat: The Radical New Approach to Nutrition That Can Burn Fat, Improve Your Health and Might Just Save Your Life. E-book. Pp. 72.
8. Taubes. Pp. 442.
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