THE GLYCEMIC INDEX AND WEIGHT CONTROL

 

Jennie Brand-Miller, PhD
Thomas M.S. Wolever MD, PhD
Stephen Colagiuri, MD
Kaye Foster-Powell, M Nutr & Diet (The New Glucose Revolution)

Obesity is now recognized as a serious and growing health concern for a large section of the American population. Between 1991 - 2000, obesity in the United State rose 60 percent. Two in three American adults are overweight and one in three is obese. Even children are effected - over 15 percent of American children are overweight. We need to tackle the problem on many fronts, including exercise and diet. The glycemic index can play an important role in weight management by helping to control appetite and insulin level.

At best - while you stick to it - a diet will reduce your calorie intake. At it worst, a diet will change your body composition for the fatter. This is because many diets employ the technique of drastically reducing your carbohydrate intake to bring about quick weight loss. The weight you lose, however, is mostly water (that was trapped or held with stored carbohydrate) and muscle (as it is broken down to produce the glucose you need to fuel your brain). Once you return to your former way of eating, your body contains a little  less muscle mass. With each repetition of a diet you lose more muscle. Over year, the resultant change in body composition to less muscle and proportionately more fat makes weight control increasingly difficult. Your body requires less and less energy to keep the engine idling.

The Real Aim in Losing Weight is Losing Body Fat. 

We will give you some important facts about food and how your body use it. Not all food are equal. When it comes to losing weight, it is not necessarily a matter of reducing how much you eat. Research has shown that the type of food you give your body determines what it is going to burn and what it is going to store as body fat. It has also revealed that certain foods are more satisfying to the appetite than others.

This is where the glycemic index plays a leading role. Low-GI foods have two essential advantages for people trying to lose weight:

1. They fill you up and keep you satisfied for longer.

2. They help you burn more body fat and less muscle.

Eating to lose weight with low-GI foods is easier because you don't have to go hungry and what you end up with is true fat release.

Why is Being Overweight a Problem ?

If you are overweight you are at  increased risk of a range of health problems. Among these are heart disease, diabetes, high blood pressure, gout, gallstones, sleep apnea (when breathing stops for a significant period of time; snoring is a good sign of this), and arthritis. Along with this list of complications, there is an equal number of emotional and psychological problems associated with being overweight.

We can tell you which foods satisfy hunger for longer and the least likely to encourage weight gain. When you use the glycemic index as  the basic for your food choice, there is no need to :

- overly restrict your food intake
- obsesively count calorie
- starve yourself 


Learning which foods your body works best on is what using the glycemic index is all about. It is also worthwhile to take control of aspects of your lifestyle that have an impact on your weight. You may not create a new body form your efforts, but you will feel better about the body you're got. Eating well and exercising is the aim of the game.

Measuring The Fuel We Need

Remember, CALORIES are a measure of the energy in food and the energy we require to keep our hearts beating and our brains working, just as a car needs so many gallons of gasoline to run for a day. Food and drink are our sources of calories. If we eat and drink too much we may store the additional as extra body fat and protein. If we consume fewer calories than we need, our bodies will break down their stores fat and protein to make up for the shortfall.

So, if you were born with a tendency to be overweight, why does it matter what you eat? The answer is that foods (more correctly, nutrients) are not equal in there effect on body metabolism. In particular, the foods you eat dictate the fuel mix that you burn for several hours after eating. If you are burning more fat and less carbohydrate, even if the energy content of the food is the same, then chances are you'll be less hungry and less likely to gain body fat over the course of the day. Consequently. your choice of foods is critical for the weight control.

Among all four major sources of calories in food (protein, fat, carbohydrate, and alcohol), fat has the highest energy content per gram, twice that of carbohydrate and protein. A high-fast food is therefore said to be "energy dense," meaning there are a lot of calories in a relatively small amount of food. A typical croissant made with wafer-thin layer of buttery pastry contains about 500 calories (which equates to about 20 - 25 percent of total energy needs for most people for the day!). To eat the same amount of energy in the form of apples, you have to eat about six large apples. So, getting more energy - calories - than your body needs is relatively easy when eating an energy-dense food.

What You Need to Know About Energy Density

A Food's "energy density" (calories per gram) is more important to weight control than its fat content.

Assessing a food's energy density has become more important than knowing its fat content. Some diets, such as traditional Mediterranean diets, contain quite a lot of fat (mainly from olive oil, but are still bulky because they are based on large portions of fruits and vegetables, including foods like legumes, which have exceptionally low GI values.

Many new low-fat foods on the market are not bulky - they have the same energy density as the original high-fat food. Examples include low-fat yogurts, ice creams, and sweet and savory snack products. So read the label - look for the energy content per 100 grams or per serving as your best guide to food's "fattening" power.

You can eat quantity - just consider the quality!

During the 1990s, one of the most notable research findings was that high fat foods were less satiating than conventional high-carbohydrate foods. For this reason, dieters were advised to stay away from high-fat foods, and the food industry responded to call for more low-fat foods.

Unfortunately, along the way, someone forgot to say that what really counts is a food's final energy density. If a low-fat food has the same energy density (calories per gram) as a high-fat food, then it's just as easy to overconsume.There are lots of low-fat products on the market that are no different from  the high-fat counterpart when it comes to calories per gram. The best examples are low-fat yogurts, ice cream, cracker and cookies.

Think Energy Density Not High Fat or Low Fat

Nutritionists have therefore had to find-tune the message ordiets for weight control:

- eating bulky food is more important than simply eating low fat
- the type of fat is more critical to long-term health
- the type of carbohydrate is as important as the amount

Why Exercise Keep You Moving

THE EFFECT of exercise doesn't end when you stop moving. People who exercise have higher metabolic rates and their bodies burn more calories per minute even when they are sleep!

The Need for Exercise

A fast metabolism is not necessarily a matter of luck. Exercise, or any physical activity, speed up our metabolic rate. By increasing our caloric expenditure, exercise helps to balance our sometimes excessive calorie intake from food.

Exercise also makes our muscles bigger (and therefore more energy demanding) and better at using fat as a source of fuel. By making our muscles more sensitive to insulin, exercise reduces the demand for this hormone and increases the amount of fat we burn. A low-GI diet has the same effect. Low-GI foods reduce the amount of insulin we need, which makes fat easier to burn and harder to store. When we eat a low-GI meal, the fuel mix being burned for the next few hours contain more fat and less carbohydrate. Since body fat is what you want to get rid of when you lose weight, exercise in combination with a low-GI diet makes a lot of sense.

Which Foods Affect Weight?

It was widely - and wrongly - believed for many years that sugar and starchy foods like potatoes, rice, and pasta were the cause of obesity. Twenty years ago, every weight-loss diet advocated restriction of these carbohydrate-rich foods. One of the reasons for this carbohydrate restriction stemmed from the apparently instant results of low-carbohydrate diets. If your diet is very low in carbohydrate you will lose weight fast. . The problem is that what you primarily lose is carbohydrate and fluid, and not fat. Moreover, a low-carbohydrate diet depletes the limited carbohydrate (glycogen) stores in the muscles, making exercise difficult and tiring.

Sugar has been blamed for obesity because it is often found in energy-dense foods such as cakes, cookies, chocolate, and ice cream. These foods, however, contain a mixture of sugar and fat - and it's the fat that makes them energy dense. If we substituted starch for all the sugar, they would still contain the same energy content. The primary sources of concentrated energy in our diet are not sweet. Fatty meats, cheese, french fries, potato chips, rich sauces, crackers, butter, and margarine contain no sugar.

Counting The Calories

ALL FOODS contain calories. Often the calorie content of a food is considered a measure of how fattening it is. Carbohydrate and protein yield the fewest calories per gram.

carbohydrate = 4 calories per gram
protein           = 4 calories per gram
alcohol          = 7 calories per gram
fat                  = 9 calories per gram

On the whole, there is scant evidence to condemn sugar or starchy foods as the cause of obesity. Overweight people show a preference for energy dense foods rather than a preference for foods high in sugar or starch because their bodies have high energy requirements, even at rest, and the easiest way to satisfy their hunger is with high-energy foods. In a survey conducted at the University of Michigan where obese men and woman listed their favorite foods, men preferred mainly fatty meats and women listed cakes, cookies, and doughnuts. The unifying trait was a lot of energy per gram of food.

How Can The Glycemic Index Help?

One of the biggest challenges to losing weight can be feeling hungry all the time, but this gnawing feeling is not a necessary part of losing weight. Foods with low GI values are among the most filling of all foods and delay hunger pangs for longer.

In the past, it was believed that protein, fat, and carbohydrate foods, taken in equal quantities, satisfied our appetite equally. We now know from recent research that the satiating capacity - the degree to which foods make us feel full - of these three nutrients is not equal.

Fatty foods, in particular, have only a weak effect on satisfying appetite relative to the number of calories they provide. This has been demonstrated clearly in experimental situations where people are asked to eat until their appetite is satisfied. They overconsume calories if the foods they are offered are high in fat. When high-carbohydrate and low-fat foods are offered, they consume fewer calories when given the opportunity to eat until satisfied. So, conventional carbohydrate foods are the best for satisfying our appetite without over-satisfying our calorie requirement.

Satiety is The Feeling of Fullness And Satisfaction We Experience After Eating. Conventional Carbohydrate Foods Provide the best satiety.

In studies we conducted, people were given a range of individual foods that contained equal numbers of calories, then their satiety responses were compared. We found that the most filling foods were those that contained fewer calories per gram, i.c., the least energy dense. This included potatoes, oatmeal, apples, oranges, and pasta. Eating more of these food satisfies appetite without providing excess calories. Foods that provided a lot of calories per gram, like croissants, chocolate, and peanuts, were the least satisfying. These foods are more likely to leave us wanting more and more to lead to what scientist call passive overconsumption - overeating without realizing it.

After energy density, the second best predictor of satiety was a food's GI value - the lower the GI value, the more the food satisfied people's  hunger. Indeed there are now more than seventeen studies that confirm low-Gi foods are able to suppress hunger for longer than high-Gi foods.

There are probably several mechanisms responsible for this.

- Low-GI foods remain longer in the small intestine, triggering receptors that tell the brain there's foods still in the gut to be digested .

- High-GI foods may stimulate hunger because the rapid rise and fall in blood-glucose levels appears to stimulate counter regulatory responses to reverse the decline.

- Stress hormones like adrenaline and cortisol are released when glucose levels rebound after a high-GI food. Both hormones tend to stimulate appetite.

- Low-GI foods may be more satiating simply because they are often less energy dense than their high-GI counterparts. The naturally high fiber content of many low-GI foods increases their bulk without increasing their energy content.

What's more, even when the calorie intake is the same, people eating low-GI foods may lose more weight than those eating high-GI foods. In a south African study the investigators divided overweight volunteers in to two groups: one group ate a low-calorie, high-GI diet and the other, a low-calorie, low-GI diet. The amount of calories, fat, protein, carbohydrate, and fiber in the diet was the same for both groups

Only the GI values of the diets were different. The low-GI group included foods like lentils, pasta, oatmeal, and corn in their diet and excluded high-GI foods like potatoes and bread. After twelve weeks, the volunteers in the group eating low-GI foods had lost, on average, 20 pounds - 4 pounds more than people in the group eating the diet of high-GI foods.

How did the low-GI diet work? The most significant finding was the different effects of the two diets on the level of insulin in the blood. Low-GI foods resulted in lower levels of insulin over the course of the day and night.

Insulin is hormone that is not only involved in regulating blood glucose levels, but also plays a key part in determining the fuel mix that we burn from minute to minute. High levels of insulin mean the body is forced to burn carbohydrate rather than fat. Thus, over the day, even if the total energy burn is the same, the proportions of fat and carbohydrate are not.

Obese individuals appear to have high glycogen (carbohydrate) stores that undergo major fluctuations during the day. This suggests that glycogen is a critical source of fuel for obese people . if glycogen is burning this makes it hard to burn the fat in food as well as the fast stored in the body. The next meal restores glycogen to its former high level (especially if the food has a high GI value) and the cycle repeats it self.

HIGH-GI MENU

Breakfast

1 cup cornflakes with milk

2 slices whole wheat toast with magarine

Snack

5  wafers

Lunch

A whole-wheat roll with ham and salad

An apple

Snack

4 slices crackerbread with cottage cheese and chives

Main Meal

Roast chicken

1 large baked potato

Baked pumpkin

Peas

A 2-inch-square sponge cake with chocolate icing

Energe Value

1,800 calories

Carbohydrate: 50% of energy

Fat: 30% of energy

LOW-GI MENU

Breakfast

¾ cup All-Bran with low-fat milk

2 slices of whole-grain pumpernicklel bread with margarine

Snack

2 small oatmeal cookies

Lunch

A sourdough roll with ham and a salad

Soft-serve vanilla yogurt with strawberries

Snack

A banana

Main Meal

Roasted chicken

1 small baked potato

1 piece of baked sweet potato

Peas

2 scoops of low-fat ice cream and ½ cup of unsweetened canned peaches

Energy Value

1,800 calories

Carbohydrate: 50% of energy

Fat: 30 of energy