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    Tuesday, September 15, 2015

    Should You Be Eating High Fat Before a Endurance Events?

      As with every aspect of the high/low carbohydrate diet argument, there is now some controversy about whether eating fat, as opposed to carbohydrate, is better for endurance sports.  Although lard has not become the preferred pre-Marathon Dinner menu item, there are some whom are promulgating for credit, even, that avoiding carbohydrates and eating fat will make you run or bike longer and faster. 1 Obviously if the only running you may do is after your spouse who is making off with the last pint of ice cream in the freezer, your response may be, “Who cares?” And if you are following a high protein, low carbohydrate diet, you may feel that exercising is irrelevant since you are losing weight without it. (The benefits of exercise on longevity, reduction of muscle loss, and delay in cognitive decline are something you will think about when you are much older).

    But maybe you have a personal trainer who tells you to avoid carbohydrates; she read that you will lose more weight exercising if you eat only fat and protein.  Or you play golf with a friend who eats six strips of bacon before a game, convinced it improves his drive.  You begin to question something you learned decades ago: that muscles use carbohydrate for fuel. Do marathoners now chow down on lard rather than pasta before a race? You begin to wonder whether eating fat before exercising will allow you to lose more weight, because it will be burned for energy. Or maybe you can exercise even better if you just eat protein. After all aren’t muscle made of protein?

    The answer is that despite what books and blogs are telling you, your body still depends on carbohydrates as its basic source of energy.

    A tiny bit of biochemistry to show you why:

    Adenosine triphosphate or ATP is the energy compound inside the cells.  It is metabolized to release the energy to allow you to pick up the remote if it fall off the sofa or to run a 100 mile ultra marathon. 2 Carbohydrates, fat and even protein can be converted to ATP with varying degrees of rapidity and efficiency. Protein is rarely used to fuel muscle movement because it has to be converted to glucose first; but it is needed to repair used muscle fibers after exercise and build new muscle. 3

    What happens when we begin to exercise? Let’s say you are walking the dog, slowly until suddenly he  jerks the leash out of your hand and races off to catch a squirrel (a futile endeavor). For the first 2 or 3 seconds, your muscles move rapidly, using  tiny amounts of stored ATP. Then, at second 4 and beyond there is no more ATP. Your muscles begin to convert  stored glucose, called glycogen, to ATP and you and your dog can happily  run for several more minutes without the need for additional oxygen. At this point, unless you supply more oxygen to your muscles, you will hurt. Lactic acid builds up causing a burning sensation and your muscles  feel tired. You need to breathe.

    In this scenario, if the squirrel runs to the next town, you have enough stored carbohydrate to run after the dog and the squirrel for about two more hours. But then you run out of stored carbohydrates and,  “hit the wall, “ or “bonk,” in athletic parlance, i.e. you run out of steam.

    So now assuming you and your dog have several miles to run to get back home, your body must switch to fat as its backup energy source.  It might be a good idea to sit down on a park bench and talk to your dog about the futility of chasing squirrels, because it takes a little time for your body to mobilize fat from your fat stores.  Unlike carbohydrate, which is readily converted to ATP, fat has to be dragged out of your fat cells (the bacon you ate for breakfast is not going to be used up on the jog home) and broken down so that  one component, the  free fatty acids, are transported to muscle cells .There they are   converted to ATP with the help of lots of oxygen. You and your dog are going to be doing a lot of  panting on the way home. 4

     Athletes who do endurance sports such as 100 mile ultra-marathons , day long mountain hikes, or long distance bike rides  can transition from carbs to fats as an energy source very quickly.  According to the sports nutritionist, Sunny Blende who writes for UltraRunning magazine, during a six hour or longer run, about 90% of energy will come from fat. 5 (My pudgy dachshund should read this Blende article).

    So does this mean that if we plan on going on for a six hour run with our dog and squirrel, we should eat lots of melted butter the night before, or at least a pint of ice cream? Well according to Ms. Blende, and I quote, “…Even the leanest ultrarunner has about 800 miles worth of fat stored within their skinny-little self.”6  Presumably the rest of us have more than  enough fat for any energy requiring endeavor,  and do not have to eat more in order to move.

    So if we can use fat for exercise, why do we need carbohydrates?  According to Matt Fitzgerald, author of Diet Cults, research done long before Dr Atkins promoted chicken fat for dieters, showed that carbohydrate is needed both for high intensity performance and endurance. He cites the diet of the Kenyan marathoners whose diet is about 78 percent carbohydrate. (They are clearly not obese). He says, “If you want to go fast, your body needs carbs for fuel.” This is true if you are running after your dog, or after a tennis ball.  

    Avoiding carbohydrates in the pursuit of leanness makes sense only if you want to avoid exercising. And if that is the case, you may need a dog that can pull you in a wagon.
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    This topic brought to you from psychologytoday.com
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