Post workout eating ice cold watermelon tastes great when you're absolutely exhausted. In doing that am I just filling my liver with glycogen while my muscles cry out for replenishment? Is the protein that accompanies the watermelon banging on the door of the muscle because the insulin hasn't arrived yet?
I was under the impression that fruit only contains the sugar fructose. However fruits have fructose and glucose in different proportions:
PREWORKOUT
These fruits provide higher fructose than glucose for sustained fuel
that won't block fat burning. Eat one or two servings.
FRUIT TOTAL SUGARS* FRUCTOSE* GLUCOSE*
Pear (1 medium) 16 11 5
Watermelon (1 wedge) 18 12 6
Apple (1 medium) 14 9 5
Cantaloupe (1/2 melon) 22 12 10
Grapes (1 cup) 24 13 11
Strawberries (2 cups) 14 8 6
Raspberries (2 cups) 10 6 4
MORNING
These fruits provide equal or nearly equal fructose and glucose to
restock liver and muscle glycogen to help halt muscle breakdown. Eat two
or three servings.
FRUIT TOTAL SUGARS* FRUCTOSE* GLUCOSE*
Pineapple (1 cup diced) 13 7 6
Honeydew melon (1 wedge) 13 7 6
Orange (1 medium) 12 6 6
Banana (1 medium) 18 9 9
Blueberries (1 cup) 14 7 7
Nectarine (1 medium) 10 5 5
Kiwi fruit (2 medium) 12 6 6
POSTWORKOUT
These fruits provide more glucose than fructose for restocking muscle glycogen and enhancing muscle growth. (The last five fruits from the morning fruit category are also decent choices postworkout, for their ability to fill glycogen stores.) Eat one or two servings along with white bread, baked potatoes or a carb drink.
FRUIT TOTAL SUGARS* FRUCTOSE* GLUCOSE*
Cherries (1 cup) 14 6 8
Peach (1 medium) 8 3 5
* Quantities are in grams.
That's all very well and good, but post workout does a sweet potato beat them all?
The Pathway Of Fructose
When you consume fructose from the foods you eat, first it gets digested and then immediately gets directed to the liver where it is stored as liver glycogen. This is much different than when it goes into the muscle cells and gets stored as muscle glycogen because the body is not going to be using this liver glycogen for fuel – at least not the nearly the same degree as it does muscle glycogen.
So, by consuming large amounts of fructose in the diet you are actually shorting yourself on the energy-deriving potential from your diet, as well as decreasing the amount of fuel that the muscles have to build new tissue with and help you see a good weight gain.
Applying This To The Post-Workout Period In Bodybuilding
So, looking at this from a bodybuilding perspective, when consuming the post-workout meal, the main objective is to shuttle as many carbohydrates into the muscle cells as they can possibly handle so they can then use this energy to build new tissues and get BIGGER.
If some carbohydrates come from fructose, this is not going to happen. Some muscle glycogen re-synthesis will occur, but it won't be maximised.
Conclusion
So, time to re-think fruit as part of the post-workout meal. Definitely do not cut the fruit out – as it’s very healthy and should be eaten, but just move it to another part of the day instead. Use starchy carbs like sweet potatoes post workout, unless I want to go all psycho on this and start supplementing with Maltodextrin/Dextrose. Let's keep it paleo eh?
References
"Supplements composed of glucose or glucose polymers are the most effective for replenishment of muscle glycogen, whereas fructose is most beneficial for the replenishment of liver glycogen."
Int J Sports Med. 1998 Jun;19 Suppl 2:S142-5. Glycogen resynthesis after exercise: effect of carbohydrate intake. Ivy JL.
"glucose polymer drink after exhaustive exercise promoted a more rapid storage of carbohydrate during the first 2 h of recovery than did consumption of an isoenergetic sucrose drink, both in the whole body and in skeletal muscle."
L. Bowtell, K. Gelly, M. L. Jackman, A. Patel, M. Simeoni, and M. J. Rennie “Effect of different carbohydrate drinks on whole body carbohydrate storage after exhaustive exercise”. Appl Physiol 88: 1529-1536, 2000;
"Fructose and fructose-containing are not optimal for glycogen storage because they are less insulinogenic than glucose, and because fructose needs to first be transformed in the liver before it can be released into the circulation as glucose and taken up by the muscle."
Nutrition and recovery of muscle energy after exercise, Décombaz, Sportmedizin und Sporttraumatologie, 2003.
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