There are quite a number of low carb diets out there, including Atkins and South Beach as well as plenty of lesser known systems.
Each of the popular low carb diets has its legion of fans who'll swear that it's the best thing since sliced bread (so to speak!).
Of course, there are some key differences between them, which are covered elsewhere on this site but this article is about what they have in common, primarly the control of sugar levels in the blood, which leads to production of fat.
The common theme is that when the body is faced with more carbohydrate than it needs (usually in the form of pasta, bread, potatoes, sugary food and so on) it produces a lot of insulin to cope with it. Insulin is a hormone that is generated in the pancreas and acts to make certain cells in the body absorb glucose (a form of sugar).
Usually it is liver and fat cells that insulin encourages to take in the glucose, and as a result, creating lots of insulin leads to the build up of stored fat in the body.
The process looks something like this at a glance:
TOO MANY CARBS (E.G. LARGE PLATE OF PASTA) = LOTS OF SUGAR IN BODY = INSULIN RISE TO COPE WITH SUGAR = FAT CELLS TAKE IN EXCESS SUGAR (GLUCOSE) = FAT CELLS FILL UP AND EXPAND
The principle behind most low carb diets is that by eating fewer carbs you are reducing the amount of insulin that is produced and therefore there will be less glucose to be absored by fat cells, and they won't expand.
Sounds easy, right? Just cut down on carbs and the weight will drop off? Well, not exactly.
It's not as simple as just checking a food label to see what's low in carbs though, as not all carbohydrates produce rises in blood sugar levels at the same rate. The foods to really watch out for are the carbs that cause a spike in blood sugar and and insulin rush. That's bad news from a dieting point of view and is also linked to diabetes.
On the other hand, some carbs release sugar more slowly and therefore are less likely to cause sudden surges in blood sugar levels. These are the carbs that are generally more acceptable as part of low carb diet plans.
The glycemic index (GI) and low carb diets
You may have heard of the glycemic index (GI) in relation to diets and nutrition. This is a great tool for finding out how quickly a food is likely to release sugar into your bloodstream. Most low carb diets use some of GI information to help dieters decide whether a food is a 'friendly carb' or otherwise.
In simple terms, the higher the GI score of a food, the greater the glucose reaction in the blood and so the key is to look out for foods that are low GI. More and more food companies are adding GI information to their food labels but it's still a fairly new area of popular nutrition, so to a large extent you are going to have to rely on yourself to get familiar with the GI levels of food.
As a rough guide, the more sugary the food, the higher the GI level. The way the glycemic index works is to allocate pure glucose a GI score of 100. All other foods are given a score relative to that, based on extensive testing of the blood sugar response they create in people.
Of course, portion size has a lot to do with the sugar effect of a meal, so a practical way of using the GI as part of your low carb diet is to work the actual GI impact of a meal, or what is sometimes referred to as the 'GI load'. This is calculated by taking the total grams of the carb and multiplying it by the GI of the carb and dividing it by 100.
You can usually find out how many carbs are in the food by checking out the label or looking it up online. Here's a quick guide to the GI score of some popular foods (all scores are averages):
- Corn flakes = 81
- Potato = 80
- Bread (white or whole wheat) = 71
- Sucrose (table sugar) = 68
- Honey = 55
- Pasta = 40s-60s
- Pinto beans = 39
- Fructose (sugar found in fruit) = 19
- Milk (full fat) = 27
- Broccoli = 0*
- Lettuce = 0
*In order to measure the GI of a food, tests usually involve the consumption of 50 grams of carbs, which is why foods that are very low in sugar and that you also wouldn't normally eat such quantities of tend to carry a GI score of 0.
Want to learn more? Find out about the myths around low carb diets.
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