Tuesday, September 25, 2007

Obesity Contributes to Vitamin D Deficiency

Lack of vitamin D can cause osteoporosis, diabetes, heart disease, degenerative arthritis, infertility, autoimmune diseases, and cancers of the breast, prostate, colon or skin. Sunlight is the best way to meet your needs for vitamin D, but dermatologists have been telling us for years that sunlight can cause skin cancer. Increased use of sunscreens use may have had the unwanted side effect of widespread vitamin D deficiency. The rise in obesity may also be contributing to increased rates of vitamin D deficiency. Once vitamin D gets into fat cells, the fat cells hold on to that vitamin so tightly that it is not easily released into the rest of the body to do its job. Furthermore, vitamin D lowers blood levels of leptin, a hormone released by fat cells to tell your brain that you are full and to stop eating. So obesity can make you deficient in vitamin D, and lack of vitamin D can make you even fatter.

Very few people are able to meet their needs for vitamin D from food. People who tan easily and are not sensitive to sunlight should probably use sunscreen only on their faces and arms, allowing their legs and backs to be exposed to the sun. However, many people, particularly those with dark skin and those who live in northern latitudes, may need to take vitamin D supplements. Check with your doctor. More

Saturday, September 22, 2007

Rest Periods Probably Do Not Increase Weight Loss

Researchers at the University of Tokyo claim that they have shown that intermittent exercise will help you to lose more weight than continuous exercise at the same intensity. Seven men participated in three different trials: 1) one hour at an intensity equal to 60 percent of maximum oxygen uptake; 2) 30 minutes at the same intensity followed by a 20-minute rest, followed by 30 more minutes of exercise at the same intensity; and 3) one hour of rest. The trial with two bouts of 30 minutes separated by a 20-minute rest burned the most fat. This intermittent exercise trial resulted in higher blood free fatty acid, glycerol and epinephrine levels, and significantly lower values of insulin and glucose.

If these researchers are correct, scientists may need to revamp their ideas about the best exercise regimen for weight loss, recommending multiple bouts of exercise with intermittent rest periods. However, there may be another way to explain the results of this study. Fat cells release fat during exercise and then reabsorb some of that fat during rest. During the intermittent exercise trial, fat cells would release fat in the first bout of exercise, some of the released fat would return during the rest period, and then during the second bout of exercise, the fat cells would appear to have released more fat because they released new fat and some of the more-soluble fat that had returned to the fat cells. The increase in fat loss would be due to the fat that had re-entered the cells during the rest period, and would not make any difference in total weight loss.

Unless the researchers can show that intermittent exercise burns more total fat than continuous exercise, there is no need to change your exercise routine. Weight loss is determined by how hard and how long you exercise, not by the timing of your rest periods. Journal reference; more on exercise for weight loss

Thursday, September 20, 2007

Prevent Weight Gain with Exercise: How Much is Enough?

Most people could eat all they want and not gain weight, but they would have to do a lot of exercising to accomplish this. A study from Zurich shows that it takes at least five hours per week of vigorous exercise to avoid gaining weight with aging (Revue Suisse de M├ędecine Praxis, May 2007). They showed that the average Swiss recreational cyclist, aged 55 to 77, has gained almost two pounds per decade from youth, compared to the non-exercising males in the same age group who gained four pounds per decade. The rate of overweight among these year-round cyclists increased from 7.4 percent in their youthful days to 25 percent by the time they reached their fifties.

If you are in an exercise program and are still gaining weight, you need to exercise more. For many people with jobs, this can be a problem. You may have to go to exercise classes in the evenings after work. Heavy morning exercise can leave you too exhausted to get through the day. You will be more likely to spend many weekend hours exercising if you have an activity that is sociable and fun. Try joining the local bicycle club or road runners club and go out for extended workouts with other members.

Wednesday, September 19, 2007

High Fructose Corn Syrup May Be Harmful: New Evidence

The food industry continues to insist that there is no difference between high fructose corn syrup (HCFS) and table sugar, but researchers at Rutgers University have a different opinion. They have found new evidence that soft drinks sweetened with (HFCS) cause tissue damage and may contribute to the development of diabetes, particularly in children. Chi-Tang Ho, Ph.D., and his colleagues conducted tests of eleven carbonated beverages containing HFCS. He found "astonishingly high levels of reactive carbonyls" in those beverages. These highly-reactive compounds associated with "unbound" fructose and glucose molecules are believed to cause tissue damage. Reactive carbonyls are not present in table sugar, whose fructose and glucose components are "bound" and chemically stable. The researchers state that reactive carbonyls are elevated in the blood of individuals with diabetes and are linked to the complications of the disease.

This study was reported at the 234th national meeting of the American Chemical Society. While we await further research, I will continue to recommend avoiding beverages sweetened with HFCS or any other sugars except during vigorous, prolonged exercise. More on high fructose corn syrup

Monday, September 17, 2007

Arch Height Should Guide Choice of Shoes for Running or Exercise Walking

Check the height of your arches when you shop for new running or walking shoes. If you have high arches, you usually need shoes with good shock absorption. If you have low arches, you will probably benefit from shoes with good motion control (Gait & Posture, July 2007).

When you run, you land on the outside bottom of your foot and roll inward. This is called pronation, which helps to protect you from injury. If you landed on your foot and did not roll, the force of the impact would be transmitted up your leg to increase your chance of breaking bones and tearing muscles. However, as you roll in from the outside bottom to the inside bottom of your foot, you will see that your lower leg twists inward. Excessive pronation twists your lower leg, which can cause stress fractures of the lower leg bones. It can cause knee pain because it forces your kneecap to rub against the bone of your upper leg. Excessive pronation can even twist your hip joint to cause pain in the hips and lower back.

People with low arches are most likely to roll in too much. Their arches may be normal but appear to be low because the ankles allow the arch to go down so far that it touches the ground. These are the people who need shoes with "motion control" to limit how far their legs twist inward. Motion control features include extra padding in the area where the arch fits in the shoe; a stiffer collar that extends from the laces to the sole to limit rolling in; and a firm stiff piece in the back of the shoe, called a counter, that grips the back of the heel to limit motion.

People with high arches hit the ground with great impact. They need running shoes that limit the force of the foot when it hits the ground. Runners with high arches should seek shoes that have soles and heels with special properties to absorb road shock. More

Wednesday, September 12, 2007

Air Pollution Should Not Keep You From Exercising

It's healthful to exercise and harmful to breathe polluted air, so how can you decide whether you are doing more harm than good? The worst time for pollution is when clouds cover the sky and automobiles fill the roads. Automobile exhaust fumes are the principal source of air pollution in most cities, and overlying clouds increase pollution. Usually the sun's rays heat the ground to warm air closest to the ground. Hot air rises, taking large amounts of pollutants skyward. On air inversion days, the clouds prevent the sun's rays from getting through to the ground, so the air near the ground is not heated, remains colder and doesn't rise, causing the air with its pollutants to remain close to the ground.

Air pollutants such as carbon monoxide, ozone, carbon dioxide, and sulfur dioxide can damage your lungs. When you exercise, you breathe more deeply and more frequently so that you breathe in more pollutants. However, you don't retain more pollution. Bicycle riders in rush hour downtown Washington traffic breathe in more carbon monoxide than car riders do, but have lower blood levels of carbon monoxide. So keep exercising, but if possible, try to avoid heavily trafficked streets, and exercise before the heavy morning traffic peak or at least two hours after the evening rush hour ends.
Should you try to breathe only through your nose?

Portion Sizes Do Matter

Whether or not you are overweight, portion sizes of food are a major factor in determining how much you eat. In a recent study, researchers at Pennsylvania State University in University Park measured how much normal and overweight people ate (Obesity, June 2007). They then fed these people fifty percent larger portions of food at every meal. Both overweight and normal weight people increased their intake of food equally and they continued to eat far more food for the duration of the study.

You might expect that when people overeat, they would eventually reach a point where they feel full and stop taking in too much food. However, this has not been shown to be the case. When people are offered large portion sizes, they continue to eat more food and it doesn't matter whether they were fat or thin when they received the larger portions. More

Monday, September 10, 2007

Repetition Makes Muscles More Efficient

Training is specific, so the more you practice your sport, the better you are able to do it. That's why triathletes who compete and train in three sports are relatively mediocre in each sport when compared to those who only run, cycle or swim. (Sports Biomechanics, Volume 6, Issue 1, 2007). In this study, elite cyclists produced significantly more effective force on their pedals than triathletes. They had far less wasted side-to-side motion, and they required less oxygen to do the same amount of work.

Repeating the same motion over and over causes your muscles to become more efficient so they can generate more power with less oxygen. For example, when you run, you use your arms to maintain your center of gravity. When your right leg moves forward, so does your left arm; your left leg and right arm move backward. Efficiency requires that you move your body forward with the least motion wasted going side to side, so that the more energy you use to drive your body forward, the less oxygen your muscles require. The same efficiency is required in pedaling a bicycle. You are supposed to move your pedals through a full 360 degrees, rather than just pushing through one phase of pedaling, and you move your body from side to side as little as possible.

In competitive sports today, the best athletes put in the most time training. Runners usually run more than 100 miles a week, cyclists often go over 400 miles a week, and weight lifters spend many hours each day in the gym lifting prodigious amounts of weights. If you want to compete at a high level, you need to spend a lot of time practicing. More on training and fitness

Thursday, September 06, 2007

Muscles Cannot Become Fat

Some people believe that if they build muscles and then stop exercising, the muscles will turn into fat. This is not a reason to avoid exercise, because muscles can't possibly turn to fat. When you exercise, your muscles become larger and stronger because exercise causes extra protein building blocks, called amino acids, to deposit in muscles. All day long, amino acids pass from your muscles into your bloodstream and then back into muscles. Exercise is the major stimulus to force amino acids back into muscles.

When you stop exercising, fewer amino acids go into your muscles so the muscles get smaller. Your body has no way to store extra protein, so amino acids that are not used in your muscles are picked up by your liver, which uses them for energy or converts them into fat for storage. So if you stop exercising, you have to eat less or you will gain weight. But muscles never turn into fat. More on muscles and protein

Wednesday, September 05, 2007

Reduce Oxidants Instead of Taking Antioxidants

Instead of taking antioxidants, researchers now think you should aim to prevent your mitochondria from making excessive amounts of oxidants. The cells of your body have tiny chambers in them called mitochondria that help convert food to energy. When they do this, they knock of electrons from nutrients, and these extra electrons eventually end up attached to oxygen. Electron-charged oxygen, called reactive oxygen species or free radicals, then attach to the DNA cells to damage them and shorten your life.

At this time, scientists have found only one practical way to reduce the amount of oxidants produced by mitochondria: exercise. Vigorous exercise helps the mitochondria burn food more cleanly with the production of fewer oxidants. The same effect can be accomplished with severe calorie restriction, or with chemicals such as resveratrol or dichloroacetate, but the results of these studies in animals have not yet been successfully applied to humans.

Here's another study showing that taking antioxidant vitamins does not prevent heart attacks (Archives of Internal Medicine, August 2007). 8,171 women over the age of 40, all with a history of heart disease or with three or more risk factors for that disease (high blood pressure, diabetes or high cholesterol) were randomly assigned into groups and given either 500 milligrams of ascorbic acid (vitamin C) every day, 600 units of vitamin E every other day or 50 milligrams of beta carotene every other day. None of the antioxidant vitamins, either alone or in combination, helped reduce the risk of a heart attack. As of today, there is no evidence that taking antioxidants vitamin pills helps prevent heart attacks. More on cell mitochondria

Monday, September 03, 2007

Partial Knee Replacement: Less Pain, but Not for Everyone

The ends of bones are soft, so they must be covered with a thick white gristle called cartilage. Many people suffer from knee pain because the cartilage is damaged. They may have osteoarthritis in which the cartilage wears away, or they may have damaged cartilage in an accident or by playing sports. Once damaged, cartilage can never heal; the person spends the rest of his life losing cartilage until the cartilage is completely gone and the knee hurts 24 hours a day.

Until recently, the only effective treatment has been to cut out the ends of the bones of the knee and replace the entire knee joint. Now for some people, a simpler procedure may be effective: partial knee replacement, called unicompartmental knee arthroplasty. The surgeon removes just part of the cartilages and bones on the upper and lower legs on one side of the knee.

However, this procedure is not for everyone. Since partial replacements are more fragile than total knee replacements and do not last as long, the patient should be over 60, not obese and not a vigorous exerciser. All of the knee ligaments should be intact, the other compartments of the knee should not be damaged, and there should be no disease, such as rheumatoid arthritis, that causes progressive joint damage. If a partial knee replacement fails, more extensive surgery will be required for a total knee replacement. If you think you may be a candidate for partial knee replacement, check with an orthopedist with experience in this procedure.

After any surgery on knee cartilage, you must protect that knee for the rest of your life. Running and jumping cause further damage, while pedaling and swimming usually do not. More on total knee replacement; more on arthroscopic knee surgery

Saturday, September 01, 2007

Awkward Running Form Can Be Improved

Many people look terribly uncoordinated when they run. Telling them to change their form will just make them more uncoordinated. If a coach criticizes a team member for poor running form and doesn't correct the underlying causes, the person is likely to become self-conscious about how he or she looks, and run even more slowly. Coordination usually improves just with repeated practice in the chosen sport.

Running form can improve markedly if you can correct muscle imbalances and structural abnormalities with appropriate exercises and perhaps mechanical devices. A coach can videotape the athletes while they run, then review the tape in slow motion to analyze the mechanical defects. For example, leaning forward during running is often caused by weak back muscles, which can be treated with exercises to strengthen the back. Pointing the toes out is often caused by weak lower leg muscles and can be corrected by doing exercises to strengthen the shin muscles. Leaning back on the heels after foot plant can be caused by excessive rolling-in motion of the feet or weak calf muscles.

Treatment often includes special inserts in the shoes and calf strengthening exercises, such as toe raises while holding a heavy weight in the hands. Holding the shoulders up towards the ears during running is usually caused by weak shoulder muscles, which can be corrected by shrugging the shoulders while holding weights. A low knee-lift is often caused by weak quadriceps muscles in the front of the upper leg. The quadriceps can be strengthened by pedaling a bicycle, skating, or running up hills. How to run faster