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Glycogen storage disease type V

Glycogen storage disease type V is a metabolic disorder, more specifically a glycogen storage disease, caused by a deficiency of myophosphorylase, the muscle isoform of the enzyme glycogen phosphorylase. This enzyme helps break down glycogen (a form of stored carbohydrate) into glucose so that it can be utilized within the muscle cell. more...

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Glycogenosis type IV
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GSD type V is also known as McArdle's disease or muscle phosphorylase deficiency. The disease was first diagnosed in 1951 by Dr. Brian McArdle of Guy's Hospital, London.

People with this disease experience difficulty when their muscles are called upon to perform relatively brief yet intense activity. The inability to break down glycogen into glucose results in an energy shortage within the muscle, resulting in muscle pain and cramping, and sometimes causing serious injury to the muscles. In addition, rhabdomyolysis—the breakdown of muscle tissue—can cause myoglobinuria, a red-to-brown-colored urine. The myoglobinuria can cause kidney damage. The disease is hereditary and is inherited as an autosomal recessive trait. Anaerobic exercise must be avoided but regular gentle aerobic exercise is beneficial.


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Fat happens: A behind-the-scenes look at fat metabolism and how to use your biology to your best advantage - managing body weight
From Muscle & Fitness/Hers, 8/1/02 by Beth Sonnenburg

"I've always joked around about my parents giving me all of the fat genes and giving my brother all of the skinny genes. Although I tried to make light of this situation, it has always been a battle for me. As a woman who has experienced weight issues as far back as I can remember, I've learned the importance of nutrition and exercise. More than 10 years ago, I lost 20 pounds by changing my diet and kept it off by eating properly (no fad diets, no quick fixes) and exercising regularly, both cardio and weight training.

"About three years ago, I was diagnosed with fibromyalgia, and was forced to decrease exercise because it was making me feel worse. Medication, surgeries and minimal overeating also contributed to weight gain. Almost all of my weight returned in a very short time. It didn't make sense to me because I was still exercising and I was still regulating my food intake, just not as well as before.

"Recently, I reworked my diet and exercise program so that I can once again weigh what I did two years ago and fit back into my clothes. I am halfway there, thanks to controlling my food intake and mixing cardio exercise with Pilates. Now that I own two businesses, and because my muscles ache all of the time, I don't get to work out as often as I'd like; however, I do make sure that I do a minimum 30 minutes of cardio five days a week and one hour of Pilates weekly.

"Will I ever be as thin as my skinny brother or skinny friends? Probably not, but I will finally accept the fact that it just isn't in me to have the same body as theirs. Will I ever be able to end this struggle with my weight? Again, probably not. It will be something I have to work hard to maintain for the rest of my life... it's in my genes."

Lisa R., California

Sound familiar? If you can relate to Lisa's struggles, you're not alone. It's a common thread we hear among M&F HERS readers, who often feel they're fighting a losing battle with biology when it comes to achieving their desired physiques. Sometimes even the tried-and-true mix of diet and exercise doesn't produce the results you want. This article covers the real deal about women and fat: eating fat, storing fat and burning fat. If you want to understand basic fat storage and metabolism, read "Fat: A Behind-the-Scenes Tour." The rest of this article covers practical advice and the most current thinking about how to win at weight loss without losing your sanity or self-esteem.


Some information courtesy of the "Voyages of a Fat Cell" presentation by Len Kravitz, PhD, at the American College of Sports Medicine Health & Fitness Summit. Kravitz is an assistant professor of exercise science and coordinator of exercise science at the University of New Mexico (Albuquerque). Visit his website at


Where: Dinner with friends

What: Salad, grilled chicken, bread, Diet Coke, carrot cake Whoo-hoo, real food's cornin' down the pipe. It's about time -- all you've given me today are scrambled egg whites and protein powder. Bleeecchhhhh. Mouth: Release some saliva to begin breakdown. Stomach: Get ready hold it all until the intestines are ready for digestion and absorption. Intestines: Prepare for breakdown and transport.

Dietary Fat's Three Major Roles:

* Fuel source for body

* Provides essential nutrients

* Gives flavor and texture to food.


Where: Stomach, intestines

What: Acidified, churning, bolus of food

Stomach: My organs and cells need some fat for cushioning and protection -- so send those lipids (another name for fat) into the intestines.

Bile: Emulsify the fat into little droplets I can work with. (Fat isn't soluble in water so it has to be broken down, absorbed and transported differently than protein or carbohydrate.) Okay, time to digest those triglycerides.

Science Speak: Triglycerides. The chief form of fat in foods.


[up and down arrow]

fatty acid + fatty acid + fatty acid + glycerol

Now I'm ready for absorption. I'll take all the bigger fat particles and lump them with some protein (forming a chylomicron) so they can travel around the body. I'll absorb the smaller particles and the glycerol through my intestinal walls. Now I'm all set to send the fatty acids on their way to pad my cells, make some membranes and maybe even clog some arteries. Oooohhhh -- did you really need those last bites of carrot cake? I'm stuffed from the salad, chicken, bread and cake. Since you've given me more than I need, some will go off to my fat cells for storage.


Where: Cells and blood

Fats can't just travel around unchaperoned -- they need a transport vehicle called a lipoprotein. Four types of lipoproteins are used, and each has just a few specific functions.

* Chylomicrons are formed in the intestines. They're made of fats and carrier proteins and they transport the fat you eat to your tissues/cells.

* Very-low-density lipoproteins (VLDLs) take fat from the liver to different tissues/cells in the body.

* Low-density liporoteins (LDLs) take over after the VLDLs have dropped some fat passengers off and picked up some cholesterol passengers. They also travel from the liver to the tissues like muscle and fat. These vehicles are associated with disease risk because they enable cholesterol deposits in the body.

Science Speak: Saturated fat. For most people, eating cholesterol does not make you have high cholesterol, It's actually the saturated fat you eat that's the culprit in high cholesterol, combined with lots of LDL to move it around and not enough HDL to get rid of it. Len Kravitz, PhD, an assistant professor of exercise science at the University of New Mexico (Albuquerque), adds that eating monounsaturated V fat or polyunsaturated fat has been shown to lower cholesterol -- but only if it's a substitute for saturated fat. In other words, dumping some olive oil on your cheeseburger won't do a thing!

* High-density lipoproteins (HDLs) are great because they do the reverse job of the LDL Instead of carrying cholesterol to the tissues, HDL takes it away to the liver for disposal. That's why it's better to have more HDL and less LDL.


What: Excess dietary fat, now broken down into fatty acids

Where: Adipose tissue (the body's fat tissue) I have more fat than I need for my basic functions, so off to storage it goes. Activate the lipoprotein lipase (LPL) to clear the fatty acids from the bloodstream and put them into storage -- do you have to ask where? Since you're a woman, you have lots of LPL in your hips and thighs, way more than a man does. That means you can break down and store more fat.

Science Speak: Lipoprotein lipase. An enzyme required to break down fat. Think of a lock-and-key mechanism, where the enzyme key is required to unlock the triglycerides so they can be split and absorbed into cells. We have more "keys" so we can "unlock" more fat.

Uh oh, my fat cells are all full. I'll have to make some new ones so I can store even more fat! Unfortunately for you, once I've made new fat cells, they'll never go away. All you can do is shrink them, but you'll always have that extra storage capacity. Since I can pack fats together tightly in my cells (they don't need water far storage like carbohydrates do), I can hold lots of them in little space.


Where: The gym, the morning after

Why: Racked by guilt over eating carrot cake, you vow to do a major calorie-burning session at the gym. Stair-stepper, here I come! Oh, it's that thing again. Maybe you'll get bored and go home ... uggghhhhh, I guess you're not joking. Better release some glycogen for fuel. I guess I'll give up some fat, too, but not too much.

Oooohhh, I'm getting tired. Epinephrine! Hormone-sensitive lipase (HSL)! Break down some of that stored fat and send it over to the mus

Cles -- we need energy! Albumin, give the fatty acids a ride to the muscles. Okay, it's here -- shuttle it to the mitochondria, our muscle cell's power plants. There we can convert it in a very complicated TCA cycle that you don't want to read about. Presto! Those fatty acids are now energy (cabries), carbon dioxide and water We'll keep doing this till you've gotten off this damn contraption.

So there you have it . . . fat metabolism 101. Of course, entire textbooks are written about this subject, but you have an idea of the biology behind your body. Now, let's maximize this information by learning how to work with it, rather than against it.


Annoyed at your apple shape? Peeved at being a pear? Here's what Christina Geithner PhD, associate professor of exercise science at Gonzaga University (Spokane, Washington), says you can change about your body shape.

Between 25% and 35% of certain body characteristics are due to genetic makeup and can't be changed. (These include percent bodyfat, fat-free mass and fat distribution.) So figure that about a quarter to a third of whatever you aren't happy with can be blamed on genetics. You can work with the rest. For example, Geithner notes that resistance training can increase fat-free mass, which is more metabolically active -- and bums more calories -- than bodyfat.

If you're an apple shape and tend to put on fat around the midsection, there's good and bad news. The bad news: Midsection weight is associated with health risks such as cardiovascular disease. The good news: It comes off easier than the pear-type weight that tends to settle in the hips and thighs.

Geithner explains that the amount and type (fat/muscle/water) of weight you lose depends on several factors:

How long you restrict your calories

How severely you restrict calories

Composition of your diet (ratio of carbs, fat and protein)

Your initial bodyweight

Your body composition

Whether or not your exercise

Type of exercise

If you just cut calories, you're likely to lose water and fat-free tissue. If you cut calories but increase your protein intake, you may minimize the amount of muscle you lose. Finally, resistance training may also minimize (but not eliminate) muscle loss.

If you're a pear, your weight isn't associated with health risks but is more difficult to lose than midsection weight. Kravitz notes that abdominal fat may be up to five times more metabolically active than lower-body fat.

Geithner advises women to focus on total calories burned, exercise and eating small, frequent meals. "You're trying to trick your body into saying you'll be fed often so you can use this fat for fuel." To lose weight and maintain your metabolism, you need to consume sufficient calories. Dropping below 1,200 calories daily can impede fat loss.


The energy you need to perform your workout comes from two primary sources: glycogen (bow glucose from carbohydrate is stored in your body) and stored fat. You usually use a combination of both while you exercise. Here are the factors that determine energy usage:

* meal prior to exercise (a high-carb meal may result in more glycogen used as fuel)

* duration (longer duration generally uses more fat)

* intensity (higher intensities use more glycogen)

* type (aerobic endurance uses more fat; high-intensity sprints, more glycogen)

* fitness level (trined people use more fat)

* carbohydrate consumed during exercise (more glycogen)

RELATED ARTICLE Q&A: Making Weight Loss Happen

* fat stored in muscle (more fat will be used).

1) HOW do you burn more fat durine exercise? Christina Geithner, PhD. has an interest in "shape shifting," or changing a person's body composition. This associate professor of exercise science at Gonzaga University (Spokane, Washington) explains: "During high-intensity, short-term exercise, glycogen is preferentially used. During low- to moderate-intensity activity, there is a greater preference for fat use. There is an even greater preference if a person is well-trained, In a trained person, the body gets more efficient at using fat -- plus, 'more fat-free mass means a higher metabolic rate." Her strategy: Become well-trained in endurance aerobic activity.

Note that in a 30-minute bout of exercise, you'll use more total calories working at a higher intensity, even though the percentage burned from fat may be less. On the other hand, you're more likely, to continue at a moderate pace rather than an all-out sprint. In addition, the moderate pace will equal out (or exceed) the calories burned during the sprint if you can last 45 minutes rather than 15 minutes. "To burn more fat, burn more calories," concludes Len Kravitz, PhD, from the University of New Mexico (Albuquerque).

2) Which aerobic activity should you choose? Geithner recommends weight-bearing exercise like jogging; running or walking. She cautions that grasping the handles on a treadmill may lessen the weight-bearing effect, and thus reduce the positive benefits available for bone health. If you use an elliptical machine or stair-stepper, beware of sloppy form that will a) abuse your body alignment and b) lessen your total calorie burn.

3) Should you do one 30-minute exercise session or three 10-minute sessions? Geithner notes that more fat will be used during the longer session, but the health benefits are probably equal in both forms of exercise -- and health should be your bottom line.

4) Should you exercise first thing in the morining on an empty stomach or eat something first? "The idea that [the former] will speed up your metabolism is not documented but for some people it will speed up their lifestyle, which may be more of a psychological pick-up," says Kravitz.

"Every semester we do a single case study with a student exercising in a fasting condition, and then after having a little carbohydrate one hour before exercising," he continues. "In each case the fasting state usually has a higher percent of fat [used], but the carbohydrate state has a greater total fat expenditure because the student can exercise longer and harder. Have a light carbohydrate snack and you'll burn more total calories."

5) Where does resistance training come in? More muscle will increase your fat-free mass, which expends more energy daily than fat mass does, thus increasing your resting metabolic rate. Kravitz likens muscle to "fat and carbohydrate-burning stoves." Adding muscle through strength training can increase the stoves' size so you're able to burn more. Kravitz advocates periodization multiple exercises per bodypart multijoint exercises and resting between sets to recover your energy.

6) Does a woman who wants to lose bodyfat really need to worry about insullin levels eating low gycemic foods etc? People get too focused on details. Focus on the positive and do what works for you. It all comes down to the energy-balance equation: calories in vs. calories out," says Geithner.

7) I've accepted that women have a bum deal when it comes to fat. We have more lipoprotein lipase more estrogen and less muscle mass. What can you say to cheer us no. "Have patience, persistence and perseverance," laughs Kravitz. "Be the best you can be and enjoy life.


It's easier for me to store fat than anything else. If you eat 100 extra calories in A the form of carbohydrate, I need around 23 calories just for the storing process. That means net storage of only 77 calories. But out of 100 fat calories, I only need to use about three for depositing, and I can store all 97 remaining calories.

factors that encourage fat storage Courtesy "Voyages of a Fat Cell" presentation


LPL (lipoprotein lipase)


Positive energy balance (too many calories in, not enough out) Physical inactivity

Ratio of fat to fat-free mass

Behavior factors

Stress hormones (such as cortisol)


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