Insulin, the Glycemic Index, and Fat Loss

Insulin is a hormone that has multiple functions, but the one most people are concerned about is its role in body fat storage. When calories are consumed, insulin is released and the more insulin there is in your system, the more calories are converted in to fat (except in special circumstances).

As a result, many popular diets focus on keeping your insulin levels down to prevent unnecessary fat storage and ultimately promote fat loss. The important thing to realize is different foods cause different amounts of insulin to be released, so you can actually help control your insulin level by eating the right foods.

Researchers have known for a long time that different foods cause your insulin levels to increase by various amounts, but it was not until the 1980's that researchers started conducting tests to quantify exactly how much insulin levels increased as a result of eating various foods. Eventually, this information was turned into a list of foods with numerical values, where the higher the number, the more insulin is released as a result of eating the food. This is now called the Glycemic Index (GI).

The Glycemic Index was initially developed to help figure out what foods are best for diabetics, but as we now know, this information is important for everyone. In general, foods with high amounts of carbs and low protein, fat, and fiber tend to have higher GI values. In addition, processed foods have higher GI values than the same food in its natural state. For example, processed white bread has a higher GI value than minimally processed flourless bread.

According to the Glycemic Index, if two people eat meals of similar sizes and ingredients, but one meal contains foods with higher GI values, the person eating the higher GI meal should store a higher number of calories as fat. For example, a 150g white baked potato contains about 27 grams of carbs and 135 total calories. If the potato is eaten with the skin, the GI value is 69, but if the potato has been peeled, the GI value is 98.

Therefore, if two people eat baked potatoes and one person eats it with the skin and the other doesn't, the person who eats the skin should store fewer calories from fat. Of course, eating a 135 calorie baked potato by itself will probably not result in many calories being stored as fat anyway, which is why the GI value doesn't necessarily give you all the information you need.

The GI value really only tells you how fast your blood sugar will rise and which foods cause more insulin to be released, assuming equal portion sizes are consumed. The Glycemic index by itself does not consider the amount of food consumed or the actual quantity of insulin released into your system, which it what really matters when it comes to fat storage.

To make up for this, another measure was devised called the glycemic load (GL). The GL value is a more accurate representation of how a given food or meal will affect your insulin response, with higher numbers corresponding to more insulin released and ultimately a higher rate of calories converted into body fat.

GI and GL values are usually expressed in terms of a single food/ingredient, but the numbers that are most important are the ones that apply to your whole meal. When dealing with glycemic index values, eating a high GI food with a low GI food will make the GI of the total meal somewhere in between. If equal quantities of each food are consumed, the total should be right around the middle and if you eat a lot of the high GI food and a little of the low GI food, then the GI total for the meal will still be high.

When looking at Glycemic load, the total meal numbers don't end up being an average as with GI values and they are cumulative instead. This is because the GL value is a measure of how much impact there is on your insulin level as a result of the food(s) you eat at a given time.

If you eat a certain amount of food and that food causes you insulin level to rise, eating additional food, even if it has a low GI value, will not cause your body to release less insulin, and it will instead add to the total glycemic load. All things being equal (eating the same foods), the more food you eat at one time, the more insulin your body will release.

A basic nutritional truth is that eating large meals results in fat gain and if you want to attain and maintain significant fat loss, one of the most important things you can do is eat small frequent meals. Larger meals result in higher insulin levels and ultimately more calories being stored as fat, which is one of the many reasons why eating large meals prevents fat loss.

GI and GL values can be useful for helping you figure out which foods can help keep your insulin levels low, but it is important to note that these values do not really tell you about the nutritional value of foods. Foods with low GI and GL values are not necessarily healthy and foods with high values are not always unhealthy.

For instance, junk foods like cake and ice cream can have low to moderate GI values, simply because they contain high amounts of fat. While these foods may not cause very high insulin responses, they will still make you fat due to their overall calorie content and lack of nutritional value.

Naturally, you shouldn't base your decisions about what foods to eat solely on the GI or GL value of a food, although eating healthy foods with low glycemic values is almost always better than eating a lot of high glycemic foods. Perhaps the best way to use these values is to find out which of the foods you currently eat are high glycemic foods. Then you can figure out if there are comparable foods with lower glycemic values that you can replace them with.

For more information about the glycemic index and glycemic load, as well as a searchable database of GI and GL values, visit: http://www.glycemicindex.com/

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14 years of experience and education in health and fitness