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Should You Eat Breakfast?

Skipping breakfast will not help you lose weight or cause you to gain weight. This month's issue of The American Journal of Clinical Nutrition contains three studies on breakfast. One study shows that whether you eat breakfast or not doesn't affect your weight at all (American Journal of Clinical Nutrition, 2014;100:507-13). Three hundred volunteers who were trying to lose weight were told to 1) skip breakfast, 2) always eat breakfast, or 3) continue their current habit regarding breakfast. Sixteen weeks later, none had lost much weight.

The second study showed that people burn calories at the same rate, and have the same body weight, cholesterol, and blood sugar levels, whether or not they eat breakfast (American Journal of Clinical Nutrition, 2014;100:539-47). Thirty-three people who were not overweight wore machines that determined how many calories they burned throughout the day. After six weeks, the breakfast eaters were more active and burned about 500 more calories during the morning, but they also consumed 500 calories at breakfast, so they neither gained nor lost weight. The breakfast skippers didn't move around as much in the mornings as the breakfast eaters, but they did not make up for their lost breakfast calories by eating more during the rest of the day.

Eating Breakfast Helps Children Function in School
The third study showed that eating breakfast improves a child's ability to solve problems and do better in school (American Journal of Clinical Nutrition, 2014;100:626-56). This study confirms many previous studies showing that breakfast benefits school children. They have better memory and attention (Appetite, 2012 Dec; 59(3):646-9), they perform better with their school work (Pediatrics, 2008 Aug; 122(2):279-84), they learn faster (Physiol Behav, 2011 Jul 6; 103(5):431-9), and they solve math problems faster and better (Physiol Behav, 2012 Jun 25; 106(4):548-55).

Should You Eat Breakfast Before You Exercise?
It depends on how hard you plan to exercise. When you are going to exercise at low intensity, you don't need breakfast. However, when you are going to take an intense workout or compete, you are better off eating first. You should eat before you try to exercise intensely for more than an hour. Your brain gets more than 98 percent of its energy from sugar in your bloodstream, but there is only enough sugar in your bloodstream to last three minutes. Your liver must release sugar constantly from its cells into your bloodstream to feed your brain. There is only enough sugar in your liver to last a little more than an hour when you exercise vigorously. When you run out of liver sugar, your blood sugar drops and your brain tells you that you feel tired. You have to take additional sources of sugar during intense exercise lasting more than 70 minutes.

Energy for Your Muscles
The limiting factor to how fast you can move your muscles over distance is the time it takes to move oxygen into muscles. Your muscles burn both sugar and fat for energy, but sugar requires less oxygen than fat does. You have an almost infinite amount of fat in your body, but store only a very limited amount of sugar in your liver and muscles. When your muscles run out of their stored sugar supply, they hurt and you have to slow down. So, you have to take a source of additional sugar when you exercise intensely for more than 70 minutes. Taking sugar while you exercise intensely increases the amount of training you can do, and does not lessen the benefits of your increased training (Journal of Applied Physiology, June 2009).

What to Eat for Vigorous Exercise
You pre-workout or pre-race meal can include anything that will not upset your stomach. However, do not take a lot of sugar from three hours up to ten minutes before you exercise intensely. Eating sugared foods or drinks can cause a high rise in blood sugar that causes your pancreas to release large amounts of insulin. Then, when you start exercising, the combination of high blood insulin levels and exercising muscles drawing sugar rapidly from the bloodstream can cause low blood sugar levels that will make you feel very tired. Instead, take sugar within five minutes before you start to exercise, and during prolonged exercise. Your contracting muscles will draw the sugar so rapidly from the bloodstream that you will not get a high rise in blood insulin level and avoid the resultant low blood sugar and tired feeling. Chocolate, jelly beans, a sugared drink or any other quick source of sugar will work.

Avoid Sugar When You Are Not Exercising
A high rise in blood sugar can cause sugar to stick to the outer surface of cell membranes. Once there, sugar can never get off and is eventually converted by a series of chemical reactions to sorbitol which destroys the cells. All of the horrible side effects of diabetes are caused by sugar sticking to cells. You do not have to be diabetic to suffer nerve, brain and blood vessel damage from a high rise in blood sugar. Therefore what is good for you during exercise can harm you when you are sedentary. Contracting muscles can draw sugar from muscles without requiring insulin, but resting muscles cannot. During exercise, sugar intake is usually harmless, but when muscles are not contracting, blood sugar levels can rise very high and damage cells throughout your body.

Checked 1/14/16

August 31st, 2014
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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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