The Glycemic Index and Weight Management
By Michael Leidig, RD, LDN

The Glycemic Index and Weight Management

More and more Americans are becoming overweight. There was once a strong correlation between low income and overweight, but now, college educated men and women are one of the fastest growing segments of the overweight population. The phenomenon is not limited to America – people in almost every country in the world are becoming overweight in record numbers.

The French are not fat!

A clue to the solution may lie in the eating habits of the one country in the world not experiencing a significant rise in fatness -- France. Fast food has never really caught on there: even the French division of McDonald's recently ran ads advising kids not to eat at McDonald's more than once a week. “There's no reason to abuse fast food, or visit McDonald's more than once a week," said a French nutritionist – in a McDonald’s ad! McDonald's Corp. in America said it "strongly disagreed" with the nutritionist quoted in the French advertisement.

The French rarely snack. They sit down to well-balanced, portion-controlled lunches and dinners every day of their lives. These meals are usually balanced. They are relatively high in protein and fat (though portions of both are small). They contain some carbohydrates, too, but these carbohydrates are usually eaten with protein and fat, not alone.

Americans are fat!

Ironically, the sophisticated French diet is closer to the high fat, high protein diet of our Paleolithic ancestors than the American diet is. When Paleolithic people ate carbohydrates, they ate them in the form of fruits and vegetables. Grains were rare and refined carbohydrates almost nonexistent.

This has led some researchers to blame human genes for human obesity: our bodies, they say, developed to cope with the Paleolithic diet. While it is true that our bodies are adept at converting food to energy and storing the surplus as fat, we can’t blame our genes for our obesity today. Most of our farming ancestors were not obese, and we were not as obese as a nation ten or twenty years ago as we are now.

The American diet has changed dramatically in recent years. Portion sizes have gone up, fat intake has gone down, and carbohydrate intake has gone way up. So has weight.

There has been an especially huge increase in the consumption of refined carbohydrates – soda, white bread, sweets – here and all over the world (except in France!). And when we eat carbohydrates, we often eat them alone – as, for example, a fast snack of chips and soda.

As Americans are eating more, many of them are also exercising less. This combination is guaranteed to make people gain weight. They will gain even more if most of the calories come from snacking on refined carbohydrates, because of the way our bodies convert food to energy.

The Glycemic Index
How what we eat affects blood sugar and energy levels

When we eat, our bodies begin digesting the food before we even swallow it: digestion starts in the mouth. Then enzymes in the stomach and small intestine extract the usable energy from the food and convert it to the only form of energy the body can use: glucose, or blood sugar. Thousands of tiny blood vessels lining the stomach and small intestine bring the glucose into the blood.

Once the blood glucose reaches a certain level, the pancreas begins manufacturing insulin and sending it into the blood. The body needs the insulin in order to use the glucose. Insulin is what withdraws glucose from the blood and pushes it into the cells – muscle cells, brain cells – that need glucose for fuel.

The more we are doing, the more fuel we need. When we take in the right foods at the right rate for our exercise level, we feel energetic. Our blood has enough glucose to fuel the cells and enough insulin to open the cells to the glucose so they can use it. Ideally, the blood contains just enough – no more, no less – of both all the time. Muscle and brain cells cannot store glucose; they convert the extra to a form of energy they can store: fat. If the muscles and brain don’t receive enough glucose, they don’t work well and we feel tired. If the muscles and brain receive more glucose than they need, we feel energetic– but only for a little while.

When we eat too many refined carbohydrates, our bodies get flooded, just as engines get flooded. When you turn on the ignition and push the accelerator too hard – put too much gas into an engine too quickly – the engine floods, and the car stalls. Refined carbohydrates pour glucose into the blood so quickly that the pancreas malfunctions and makes too much insulin. The excess insulin floods the muscle and brain cells with glucose, leaving none in the blood.

Within a few minutes, we don’t have enough glucose – even though we have just eaten a huge amount of food! (Remember, muscle and brain cells cannot store glucose –the extra gets converted to fat.) Eating refined carbohydrates makes blood glucose levels fall so quickly that after the initial rush of energy, we feel increased hunger and fatigue. This often leads to eating more refined carbohydrates, which starts the whole cycle all over again. Blood glucose soars and crashes, more extra glucose is stored as fat, and the eater is more tired than ever!

What produces energy efficiently is a slow, steady supply of blood glucose: a supply strong enough to fuel the cells, but slow and steady enough not to overwhelm the system – “flood the engine.” According to the latest research, this is best produced, not by carbohydrates alone, but by a mixture of protein and fat, which slow digestion and cause satiety, and carbohydrates. Carbohydrates supply the body with sustained energy only when they are eaten with protein.

The Glycemic Index

Researchers have studied the effect different foods have upon blood glucose levels. This research has produced an index comparing foods, the glycemic index. The glycemic index ranks foods according to how much they increase glucose levels for two or three hours after they have been eaten. Some of the results surprised researchers. Foods high in fat and protein, they found, raise blood glucose levels more slowly and gradually than carbohydrates alone.

Even more surprisingly, carbohydrates themselves differ in their effect upon blood glucose. Most refined carbohydrates raise blood glucose levels very rapidly: Sticky white rice, for example, is 98 on the index, almost as high as pure glucose (100). However, some unrefined carbohydrates raise blood glucose levels quickly and dramatically; others do not. Whole wheat bread, for example, raises blood glucose levels much more rapidly than plain old spaghetti does. This is because bread is made of wheat flour and pasta, even white spaghetti, is made of semolina or cracked wheat, which take longer to digest.

Certainly the glycemic index of a food isn’t the only factor influencing weight loss. However, it is one tool that can help fine tune a weight management program to promote better weight loss and blood sugar control. The goal is to keep you steadily supplied with energy (keep your blood glucose at a steady level) so that you feel satisfied and energetic – in a state of sustained well-being, all day long.

*This material is not intended to substitute for medical advice from your doctor. Please consult your health care provider before changing your eating and exercise patterns.

© 2008 Nutrition & Fitness Advisors. Reprinted with permission.

Michael Mansueto Leidig, RD, LDN is a Registered Dietitian and Certified Personal Trainer. He is the founder of Nutrition & Fitness Advisors a telephone-/internet-based nutrition and fitness consulting practice www.myhealthadvisor.com.

In addition, he is the Associate Director of the PRIORITY adolescent weight management program at Tufts Medical Center in Boston, MA. Michael is a nationally recognized speaker on weight management and the glycemic index.

He has made television / radio appearances and co-authored book chapters and journal articles. Since 2000, Michael has worked with adults, adolescents, and children offering the latest research-based weight loss advice in a convenient, enjoyable way.

Michael guides clients through all phases of the change process including discovery, planning, and implementation. His method is not based upon deprivation, but upon knowledge, motivation, action, and attention to the moment. Michael believes that making the commitment to healthfully nourishing yourself is a great step towards being and feeling your best.

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