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Fasting Two Days a Week May Benefit Your Brain

Researchers at the Johns Hopkins School of Medicine have collected evidence that reducing food intake to under 500 calories per day for two days a week may help to prevent brain damage from Alzheimer's or Parkinson's Diseases (Annual Meeting of the American Association for the Advancement of Science in Vancouver, February 19, 2012).

FASTING GROWS NEW NERVES: Mark Mattson of Johns Hopkins has shown that fasting increases the growth of new neurons in the brain, and this can help prevent dementia. He believes that: "The cells of the brain are put under mild stress that is analogous to the effects of exercise on muscle cells."

He also showed that skipping meals stimulates brain cells in mice to produce Brain-Derived Neurotrophic Factor (BDNF) that causes the brain to grow new nerves, helps protect nerve cells from being damaged by toxins, and helps mice learn new things.

SKIPPING MEALS PROTECTS THE BRAIN: Earlier studies showed that mice who fast every other day while eating double the normal amount of food on non-fasting days have better protection from becoming diabetic (lower insulin and sugar levels), and less brain damage from poisons than mice on 40 percent calorie-restricted diets {Proceedings of the National Academy of Sciences, May 13, 2003; 100(10):6216-6220; and The Journal of Nutrition, June 2003;133 (6): 1921-1929}. Meal-skipping mice gorge when provided food so they do not eat fewer calories than mice on unrestricted diets.

In the same study, mice were given a chemical, called kainate, that damages nerves in the same part of the brain damaged by Alzheimer's disease. The meal-skipping mice had far less brain damage than those who were on a 40 percent reduced calorie diet.

EXERCISING HELPS YOUR BRAIN STORE MORE GLYCOGEN: More than 98 percent of the energy for the brain comes from sugar in the bloodstream. Ten years ago, it was shown for the first time that certain brain cells, called astrocytes, store sugar in the same way and form (glycogen) that muscles store sugar. Like muscles, the brain can store extra glycogen and like muscles, the brain will have greater endurance and function better when it stores more glycogen.

During exercise, your brain uses up tremendous amounts of sugar, directing each muscle fiber to contract and relax. It takes a lot of energy to do this. Recently, a study from Japan showed that when rats exercise, their brains use up their stores of glycogen in the same way that muscles use up glycogen (J Physiol, August 15, 2011;589(Pt 16):4079). When the rats ate after exercising, their brains, like their muscles, were able to store up to 60 percent more glycogen than they could before they exercised. After 24 hours, their brain levels of glycogen dropped to their previously lower levels.

However, when the rats continued to exercise regularly for four more weeks, their brains were able to store much higher levels after eating and the levels did not drop soon afterwards.

WHAT DOES THIS MEAN FOR YOU? Future studies will tell if intermittent fasting is more effective than overall calorie restriction in preventing and treating dementia in humans. Meanwhile, you may want to try intermittent fasting to lose weight or to avoid the weight gain that often comes with aging. The recent studies shows that adding exercise to intermittent fasting may make you even smarter.


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How Excessive Food Intake Damages the Brain

Older people who consume more than 2,143 calories a day have more than double the risk of memory loss called mild cognitive impairment (MCI), compared to those who ate fewer than 1,500 calories a day (To be presented at the American Academy of Neurology's 64th Annual Meeting in New Orleans, April 21, 2012). People with MCI have problems with memory, language or thinking severe enough to be noticeable to other people and to show up on tests, but not serious enough to interfere with daily life.

THE STUDY: Participants ages 70-89 reported the amount of calories they ate or drank in a food questionnaire and were divided into three equal groups: 600-1,525 calories per day, 1,526-2,143 per day, and 2,144-6,000 per day. The more calories the participants took in, the higher their risk for MCI.

Many other studies show that obesity increases, and caloric restriction decreases, risk for Alzheimer's. Anything that is bad for the heart is bad for the brain, and people who eat too much are at increased risk for heart attacks, strokes, diabetes and memory problems.

RESTRICT CALORIES: People in their 70s and 80s who do not exercise regularly should not take in more than 2,100 calories per day. Animal studies suggest that it is the excess fat formed by overeating, and not just the excess calories, that damages the brain. This means that regular exercisers can take in more calories, as long as they are not gaining fat.

HOW FAT HARMS YOUR BRAIN: Full fat cells send out cytokines that turn on your immunity. Your immunity is supposed to be used only to kill organisms that invade your body and abnormal cells such as cancer cells. They kill invading organisms by producing chemicals that dissolve the outer coatings of bacteria and send out antibodies that attach to and kill the invading organisms. When your immunity stays on all the time, these same defense mechanisms dissolve your own tissues and kill your own healthy cells. Being overweight damages every tissue in your body, including your brain.



Injuries upset athletes because they know their competitors are still training. A recent study from the University of Exeter in the United Kingdom shows that TRAINING INTENSELY IN ONE ARM MAKES THE OTHER ARM MUSCLES STRONGER ALSO (European Journal of Applied Physiology, March, 2012;112(3):1005-13). This means that:

• When you are injured, you can maintain fitness in your injured limb by exercising the opposite limb.

• When your muscles hurt from, a hard training session, you can become stronger by exercising at low intensity than you can by taking the day off. Doing any movement repetitively teaches your brain to contract more muscle fibers simultaneously which makes you stronger (see explanation below).

STRESS AND RECOVER: Intelligent sports training is done by stressing and recovering: On one day, take a hard workout intense enough to damage your muscles. You know that you have damaged your muscles because you feel sore on the next day. Then you take easy workouts for as many days as it takes for the muscles to heal. You can tell your muscles have healed because the soreness goes away.

THE EXPERIMENT: The authors of this study know that multiple bouts of hard exercise make muscles stronger. So they tested whether doing multiple bouts of exercise in one muscle group of one arm will make the other arm muscles stronger, and they found that it did.

ECCENTRIC CONTRACTIONS: The type of exercise that does the most damage and can cause the most muscle growth is called ECCENTRIC. This means that the muscles are stretched when they contract, such as trying to lower a weight slowly, rather than trying to raise it rapidly. The subjects tried to hold a muscle contraction when the muscles were stretched. They performed two bouts of 60 eccentric contractions of 30 degrees separated by two weeks. Both bouts were performed on the "exercised" arm, while only the first bout was performed in the "resting" arm. After the second bout of exercise for the twice-exercised arm, the once-exercised arm was stronger, and had less soreness and reduction in angle of arm movement, than it had after the first bout.

WHY ONE ARM STRENGTHENS THE OTHER: Each muscle contains millions of fibers, and each fiber is stimulated by a single nerve. When you exercise, your brain sends messages along these nerves, telling only about five percent of the nerves to contract at the same time. With training, your brain learns to contract a greater percentage of muscle fibers simultaneously. The more you practice a specific exercise, the greater percentage of your muscle fibers you can contract at the same time. When you stop exercising, your brain quickly loses its ability to contract as many fibers at the same time and you lose strength, endurance and coordination. However, if you continue to exercise one arm, your brain retains its ability to contract more fibers in the opposite arm.

WHY THE AUTHORS USED ECCENTRIC CONTRACTIONS: Several experiments show that cross-transference is even more effective when the athletes used eccentric, rather than concentric, training (Med and Sci in Spts and Ex. 1997 (Jan); 29(1): 107-112. We know that you become stronger by exercising against greater resistance. The heavier the weight that you lift, the greater the gain in strength. A person can lower a heavier weight than he can lift when gravity works with him.

CROSS-TRANSFERENCE CANNOT BE EXPLAINED BY CHANGES IN BLOOD FLOW: It does not increase blood flow to the other arm (Journal of Sports Medicine and Physical Fitness, 2000;40(2):110-117).

CROSS-TRANSFERENCE PERSISTS: In one test of cross- transference, the One-Repetition Maximum (the heaviest weight a person can lift once) persisted over eight weeks of de-training (Journal of Orthopaedic & Sports Physical Therapy, November 1955;22:5:207-215).

ONLY ON OPPOSITE LIMBS: This concept applies only to opposite limbs. You can maintain strength in an injured arm by continuing to exercise the uninjured one, but exercising your legs will not strengthen your arms and vice versa. So if you are a runner who injures a leg muscle, you can work the uninjured leg on resistance machines to keep up the strength of both legs. If you are a baseball pitcher, you can help to maintain strength in an injured arm by using your other arm to throw and do resistance exercises.


Recipe of the Week:

Extra Quick Chili

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February 26th, 2012
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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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