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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 (Journal of Applied Physiology, June 2007). 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.


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Dear Dr. Mirkin: Should I be concerned about 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 lower 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.


Dear Dr. Mirkin: Why is exercise so important for control or prevention of diabetes?

Diabetes damages every cell in your body to cause heart attacks, strokes, blindness, deafness, kidney failure, and impotence. A review of the literature from the University of Missouri–Kansas City shows that virtually all these horrible consequences are caused by a high rise in blood sugar after eating (The American Journal of Cardiology, September 2007). When blood sugar levels rise too high, sugar sticks to cells. Once stuck on a cell surface membrane, sugar cannot get off. It is converted to a poison called sorbitol that destroys the cell to damage tissues throughout the body.

Exercise helps to prevent a high rise in blood sugar after eating. Sugar can only be stored in muscles and the liver. After a person eats, sugar passes from the intestines into the bloodstream. If the muscles are full of sugar, sugar spikes to high levels and damages cells. On the other hand, if the muscles are empty, sugar passes from the intestines into the bloodstream and then into muscles and does not rise to high levels in the blood stream. Diabetics live longer, and have fewer heart attacks and strokes, when they prevent the high rise in blood sugar levels after eating.


Recipe of the Week

Root Veggie-Lentil Soup

Hand blender(great for soup-making) and other kitchen tools

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

June 26th, 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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