Exercising on an empty stomach?

My main meal is in the pm so I usually run on empty...anything from short runs to 15km or more. For me, water is the key...I drink lots and always have but if for any reason I drink less than normal one day, my workout suffers the following day. Even if I drink plenty just before exercising. If I have to exercise after eating I have to wait at least 2 hours or I feel quite churney and not great at all.

I am not a scientist and have not looked at any research regarding the fasted vs nonfasted cardio debate.

With that disclaimer out of the way I can say that I have done both for extended periods of time due to work schedule. I used to workout in the early AM fasted, cuz I liked to eat breakfast at work. Then my schedule changed and it became more conveniant to workout after work, and since I wasn't going to fast all day cuz I like to eat:) I would workout after eating my afternoon snack. Just the way the timing worked out. I noticed no improved loss of BF% one way or the other. As long as I got in my workouts and stuck to my cal goal I lost weight at the same pace both ways.

Do whatever works for you.

I personally can't exercise on a completely empty stomach, I feel too weak and get dizzy. So I either eat and wait an hour or two (depends on what I eat / how heavy it is) or I eat a light snack before I get busy.

I've read different articles about this, some saying a small pre workout snack is good, fuels you, etc. And others saying to work out on an empty stomach so your body doesn't have so much fuel to work from that it doesn't start using fat as fuel. (Or along those lines anyway, you know what I mean!)

And I should say I don't mean working out having not eaten for 2 days, or you're so hungry you're in pain! I workout when I get up in the morning, and say if I get up at 7am and haven't eaten since 7.30pm the previous night, is it ok to work out on an empty stomach? I don't find that I get fatigued or lightheaded after/during my workout.. And I always make sure to refuel straight after!

Just wondering what works for you and has ether option helped/hindered your fat loss?

Given a subject who is untrained but normally nourished, if they exercise at 70% VO2 max, they will exhaust liver and muscle glycogen.

What I just wrote means that you have to work very, very hard to deplete all of your glycogen unless you're running about 20 + miles.

Pick up a copy of "The Lore of Running" by Dr Time Noakes and read through chapter 2, esp around page 98 (going from memory).

While we navel gaze about minute amounts of nutrients, we are doing that from a body that has spent 5,000,000 years figuring out how to survive. We wouldn't have lasted this long if we needed to stock up on food before we went out to do what is, in the big scheme of things, small amounts of exercise.

Having said that, some folks don't do well without something extra in the tank (that's who the sabertooth would snack on!). Much of that is psychological (not surprising since most of us are here we had an eating disorders at some time) but losing weight and running can kick your butt (I recently dropped about 5 pounds in 10 days and things got pretty tough at times).

Your body will always use some percentage of fat as fuel. It varies with a huge number of factors but your body will switch between fuel sources in real time. I have a trace that shows how my CHO/fat percentages sitting vs moving about the house. Sitting I was burning 60% fat ---- as soon as I stood up and walked up the stairs, fat % plummeted and CHO levels took off. When I got to the second floor of the house, the percentages reverted.


Here are some links to some images:

cbeinfo.net/running/images/hr_vs_fatpercentage_running_20130125.jpg
cbeinfo.net/running/images/hr_vs_fatpercentage_sitting_20130213.jpg
cbeinfo.net/running/images/hr_vs_fatpercentage_walking_20130127.jpg

Those images are from the .FIT file generated by a Garmin 610 with R-R recording activated (the top of the line Polar and Sunnto HRM's have that option) The file was opened and analyzed using FirstBeat Athlete software.

Some comments:
1 - there is no medical evidence to substantiate a claim that it is "dangerous to workout on an empty stomach". During endurance training (long distance running), it is a common tactic to train without taking on fuel. The goal is to force the body to use fat as a fuel (because even skinny people have many pounds of visceral fat) instead of burning glycogen (which most of us here on MFP have well under half a pound of glycogen in our bodies)

2 - the amount of water we ingest prior to or during exercise has, for practical purposes, no impact on an exercise of short duration, regardless of temperature. Of course, that's an anathema to "drink, drink, drink" crowd but understand that just as much as there is zero medical basis that we need "8 glasses a day"*, medical research clearly indicates that all we need to do is "drink to thirst" and we will be able to do things like run marathons in high temperatures.**

How is that possible?
The older remains of our species were discovered in the Olduvai Gorge in the Rift Valley in Africa (http://en.wikipedia.org/wiki/Olduvai_Gorge) . We survived because we adapted our bodies to be able to chase down prey until it died of heat exhaustion. Yes, a gazelle can outrun human in a short distance race but, because humans have such incredible heat dispersing capabilities, our ancestors would track the animal, wait until it faltered, and then finish it off.
Our species simply would not have survived if we needed to "pre-drink"


*Drinking lotsa water has benefits for some folks when losing weight - it helps loosen you up if you're constipated; it's really hard to eat if you've got a water bottle in your hand; and it can fool your stomach because you feel full. Other than that, nada thing.

Refer to the research by Dr. Valtin and even Snopes has dealt with topic:

http://www.ncbi.nlm.nih.gov/pubmed/12376390
http://www.dartmouth.edu/~news/releases/2002/aug/080802.html
http://ajpregu.physiology.org/content/283/5/R993.full


**Ref "The Lore of Running" and also "Waterlogged" a newer book by Dr Noakes in which he explains how water and thermoregulation function during exercise and he also details how the "need to drink" water and energy drinks coincides very, very clearly with the discovery and marketing of Gatorade.

I work out at 5 am so I generally don't eat before. I used to grab a banana on the way out the door but found I really didn't need it as long as a refuel after I get home!

I've recently started working out first thing in the morning. I get up, throw on exercise clothing, have a quick cup of java and a small bowl of oatmeal with berries and protein powder, then head straight to the gym. Not enough food to make me bloated, but enough to give me energy to begin exercising. Working fairly well so far whether it's a lifting day or cardio day.

Unless I'm running above 15 miles I can generally do it without issue provided I'm smart about dinner the night before.