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Skinny Without Willpower

Wednesday, April 1, 2009

Good Carbs vs. Bad Carbs: Introduction to Glycemic Index.

If you gathered from my last post that all carbs are the nemesis of successful weight-loss programs then I am sorry to give you that impression. Actually carbs are a very important component of our diet and half our calorie intake must come from carbs. Fruits, we all know, are very healthy and packed with essential vitamins and minerals, not to mention anti-aging antioxidants, have plenty of carbs in them and everyone should have at least 2-4 servings per day. Even the RDA food pyramid suggests 8-12 servings of carbs per day.

So obviously all carbs aren’t created equal! This is where Glycemic Index (GI) of a carb comes into play. In simple terms GI of a carb is its ability to affect the blood’s glucose level relative to glucose. The GI value of glucose (or dextrose) is assigned 100. Another concept is the Glycemic Response (GR) which is a measure of how fast blood glucose levels rise with the consumption of a certain type of carb. So as you may have already guessed the higher the GI value of a carb the faster the GR in the body and the faster the insulin response of the pancreas. For example a boiled potato (GI 85) spikes our blood glucose level in milliseconds while garbanzo beans (GI 28) takes about an hour to gradually raise the blood glucose levels. This would mean that eating a boiled potato would spike your insulin level in a matter of few minutes and as soon as the insulin levels rise it would start converting and stacking away the excess blood glucose into your fat cells, provided no physical activity (or the need for the excess glucose) was being performed to utilize the glucose . Once all the blood glucose from the potato was stacked away into your fat cells the residual insulin would still keep acting on your glucose levels further reducing its supply and making you hungry in the process. And once you repeat the carb eating process the same insulin cycle continues over and over again. Over a period of time this causes a sort of insulin resistance in your body where more and more insulin needs to be released to counteract the same glucose levels. In extreme cases the pancreas just give up and stop the insulin release that leads to other complications of elevated glucose levels, as in people with diabetes. On the other hand something like garbanzo beans would slowly raise the blood glucose level and chances are the body would be using up the small amounts of glucose that is produced for its normal day-to-day activity without ever converting to fat.

In order to start burning the stored fat, calories burned in the body should exceed the calorie intake. A sensible exercise program coupled with a caloric restrictive diet can accomplish that. Secondly and more importantly in order to stop accumulating any new fat, the calories should come from sources that don’t cause sudden insulin spikes, i.e., from low GI sources taken in small quantities over several small meals. This way insulin levels are stabilized to a steady level through out the day and there is no additional fat accumulation. That is easier said than done especially for someone like me that spent a good part of life believing in the high-carb-low-fat dogma for fat loss. I never paid attention to the carbs I ate as long as they were low in fat. I cut down on fat drastically while consuming big portions of white bread, rice, potatoes and even soft drinks (since they were ‘zero fat’) and you don’t want to know the results of this ‘sensible diet’.

The concept of South-beach is to get ones body off the insulin dependence in the initial 2 week phase. This increases ones metabolism since the body has to now work harder in order to convert calories from low GI sources and proteins. During this phase all the calories come from very low GI foods such as Garbanzo beans, lentils, lean meats, fish, nuts etc, spread out over several small meals throughout the day. During the first 2-3 days the body is craving the high insulin levels and it might seem like one is perpetually hungry and ‘weak’ but once the body gets past this threshold it becomes easier and the body doesn’t crave the insulin levels. After about a week on this diet one would no longer crave the usual comfort carbs (rice, potatoes, and bread) and it would seem like you are never hungry enough to indulge in binge eating. Life is easier after that. People, depending on how over-weight they were to begin with, lose an average of 10-20 lbs in the first two weeks. After the initial 2 week phase one goes on a phase 2 where some of the carbs that were forbidden in phase 1 are re-introduced in the diet, like whole wheat bread, whole wheat pasta, fruits etc. Phase 2 can be continued for as long as one desires and there is typically continued weight loss of about 1 lb/week until weight loss stabilizes. At that point some go on a phase 3 where some more of the carbs are introduced and typically you are allowed ice cream and some other desserts. Phase 3 is very easy and can be practiced for life and as long as you have a balanced meal of low to moderate GI carbs, healthy fats and protein.

If phase 1 sounds too difficult (and believe me it is) then one can simply begin with phase 2 coupled with an exercise regimen that will help boost metabolism and keep insulin levels low (remember exercise lowers insulin by consuming excess blood glucose). With this approach the same goal is achieved as phase 1 where the metabolism is boosted and the body gets off insulin dependence. The best of course would be to go into phase 1 coupled with an exercise regimen, but that is even more difficult especially in the first week of adaptation phase where perceived energy levels are low and exercising might be next to impossible.

Here is a pretty comprehensive listing of the GI values of the most common foods.

Use this list to pick your favorite food and stick to the low to moderate GI foods. Occasional indulgence in high GI comfort foods is allowed after physical exercise as at that point the insulin levels are low. Better even combine those high GI foods with healthy fats and proteins so that the overall effect of high GI is blunted as proteins and fats hinder the quick absorption of high GI foods and keep you fuller longer. Happy eating and exercising and fat loss….Until next time.



  2. I'm not sure if you have used this website before, but it is a good place to get a general idea of nutritional facts of common foods. Couple yrs ago they added the Estimated Glycemic Load to their nutritional facts data.