Many popular diets are based on the glycemic index---The Zone, South Beach, Nutrisystem and the Atkins Diet, for example. Compared with high-GI foods, low-GI foods have a minimal affect on your glucose levels, which helps stabilize blood sugar and ensure that your body does not produce too much insulin. Large amounts of insulin in your bloodstream may trigger sugar cravings, which will sabotage your weight-loss efforts.
Glycemic Index Basics
Only carbohydrates are scored on the glycemic index, because only carbohydrates raise your blood sugar. Fiber, fat and protein actually slow the absorption of sugar into your bloodstream. All carbs are ranked in comparison to pure glucose, which scores a 100 on the GI. Low-GI foods score less than 55, intermediate-GI foods score between 55 and 69 and foods that score higher than 70 are high-GI foods. Generally, weight loss programs based on the glycemic index recommend you eat mostly low-GI foods.
Are All Low-GI Foods Healthy?
Almost all vegetables score low on the glycemic index --- as do most fruits and a few whole grains, such as rice and barley. But because fat slows the absorption of sugar, many high-calorie, high-fat foods are low on the glycemic index, too. Whole milk scores a 27, and skim milk is a 32. An orange, nutrient-dense but containing natural sugars, scores a 44, but a high-fat Snickers Bar scores lower --- a 40 on the GI. Using the glycemic index alone, Peanut M&Ms would be a better choice than an apple, and ice cream and apricots would be equally healthy. So you have to keep this in consideration. At best, the glycemic index is only a guideline for healthy eating.
Reducing Calorie Consumption
One reason diets based on the glycemic index may help you lose weight is that they tend to be higher in protein, fat and fiber. These three nutrients can help you feel full longer and eat less food at each meal, reducing your total calorie consumption. Weight loss is simply a matter of burning more calories than you consume, so eating fewer calories is a step in the right direction. A good low-GI diet will also include regular exercise to help burn even more calories.
Stabilizing Blood Sugar
Low-GI foods don't cause quick spikes in blood sugar. The danger with a dramatic increase in blood sugar, is that it's often followed by an equally fast drop, leading to hypoglycemia, or low glucose levels. Hypoglycemia triggers a sugar craving, as your body needs more glucose. If you give in to your craving for sugar, you might start the cycle over again, alternating between high and low blood sugars, eating too much food and gaining weight. Eating foods low on the glycemic index can break this cycle and eliminate sugar cravings.
