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Obesity and High-Fat Diet May Both Prevent Muscle Growth

A study from the University of California, Davis shows that a high-fat diet prevents exercising mice from enlarging their muscles (Journal of Physiology, December 2010). The mice received either a low fat, high carbohydrate diet or a high fat, low carbohydrate diet for 14 weeks. Each group was divided into those who performed progressive resistance exercises with their plantaris muscles or those that did not do this exercise. Those who exercised on the low fat, high-carbohydrate diet had substantially larger muscles than those who exercised on the high-fat diet. Chemical analysis of their muscles showed that the high fat diet group had lower levels of polysomes (Akt and S6K1) necessary for making protein.

If this study can be applied to humans, it will mean that not only does a high-saturated-fat diet make you fatter, it also keeps you from enlarging your muscles. We know that both full fat cells and eating large amounts of saturated fats (the dominant fat in meat) turns on your immunity to cause inflammation that can prevent the body from making protein necessary for enlarging muscles. (Journal of Nutrition, January 2009). A high saturated-fat diet also blocks insulin receptors and thus prevents your body from responding to insulin, which is necessary for muscles to heal from intense workouts. Insulin drives amino acids, the protein building blocks, into muscles to help them heal faster. Anything that blocks muscles' ability to respond to insulin will decrease amino acid entry into muscles and thus delay healing so you can't recover as fast for your next workout. Further journal references and recommendations


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Dear Dr. Mirkin: How does dried fruit act to prevent constipation?

All carbohydrates are made up of combinations of sugars. Before any carbohydrate can be absorbed, it must first be broken down into single sugars that are almost always absorbed before they reach your colon. Only single sugars can be absorbed. Dried skins of fruits contain fiber that your body cannot break down, and sugars imbedded so deeply in the fiber that these sugars cannot be absorbed in the small intestines. When these sugars reach the colon, bacteria ferment them rapidly and break them into 1) small particles that draw large amounts of fluids into the colon, and 2) gas that dilates the colon and pushes stool toward the opening.

When you eat, the pyloric sphincter at the end of the stomach closes, and food is not allowed to pass into your small intestine until is converted to a liquid soup. Nutrients are absorbed from the food there, but most of the liquid soup passes to your colon, where the fluid is rapidly absorbed. As a general rule, food reaches your colon four to ten hours after you eat, but it can remain in your colon from many hours to many days, depending on when you push it out. The longer stool remains in your colon, the more water is absorbed, the harder stool becomes, and the more difficult it is to pass. To prevent or treat constipation, try to move everything from your colon as soon as possible.

If you have chronic constipation, check with your doctor who will probably order tests to rule out a cancer or other obstruction, or diabetic nerve damage. Usually these tests are normal and you need to change your diet.

• Exercise every day. Exercise causes giant contractions of the colon which push food out. The longer and harder you exercise, the greater the movement of food toward the outside.

• Drink plenty of fluid because dehydration increases the rate that fluid is absorbed from your colon.

• Avoid constipating foods: low-fiber foods such as flour and sugar water; and high-fat foods such as cheese, eggs, and meats.

• Eat lots of high-fiber foods that hold extra water in your colon: vegetables, whole grains, beans, fruits, nuts.

• Dried fruits are particularly effective for pushing food onward: prunes, apricots, cranberries, apples and so forth.

• Try to empty your colon less than a half hour after eating. When food reaches your stomach, the stomach is stretched, sending a message along nerves from the stomach to cause the colon to contract and push foods forward. This is called the gastro-colic reflex. The longer stool remains in your colon, the drier and harder it becomes, so you want to empty your colon as soon as it fills.


Dear Dr. Mirkin: Will drinking a beer before a race slow me down?

Yes! In one recent study, trained cyclists drank an ounce of alcohol before a 60-minute time trial and had a significant reduction in average cycling power, oxygen consumption, carbon dioxide production and glucose oxidation and an increase in heart rate response and ratings of perceived exertion (Alcohol and Alcoholism, May-June 2009).

Alcohol reduces the force of the contractions of your heart so that it can't pump as much blood through your body. It increases the amount of oxygen that your body needs, so you tire sooner. It increases sweating so you dehydrate earlier, and it causes muscles to use up stored carbohydrate faster so your muscles feel heavy and hurt.


Recipe of the Week:

Extra-Quick Chili

You'll find lots of recipes and helpful tips in The Good Food Book - it's FREE

June 21st, 2013
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About the Author: Gabe Mirkin, MD

Sports medicine doctor, fitness guru and long-time radio host Gabe Mirkin, M.D., brings you news and tips for your healthful lifestyle. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. He is board-certified in four specialties: Sports Medicine, Allergy and Immunology, Pediatrics and Pediatric Immunology. The Dr. Mirkin Show, his call-in show on fitness and health, was syndicated in more than 120 cities. Read More
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