Glycemic index, or GI, is a measurement used to determine how quickly a particular food is converted to glucose, a necessary nutrient for fueling muscle and brain cells. Glucose spikes can be a problem when trying to control energy levels and manage weight. When a high GI food is consumed, glucose is broken down quickly, making it readily available within just a few minutes. This is important for athletes participating in endurance events who need to be fueling regularly. However, when someone is more sedentary, a high GI food can cause a spike and crash of energy, leading to negative consequences such as finding it difficult to concentrate, experiencing unstable mood swings, feeling sleepy or sluggish, and increased fat storage. Consumption of a low GI diet has been shown to help to control appetite, and may be beneficial at preventing diabetes, heart disease and obesity.
High Glycemic Foods
High GI foods are not bad foods, but unless you are doing physical activity, it is best to choose low GI foods or combine a high GI food with a low GI food for a lowered glycemic response. Carbohydrate-only foods such as bread, cereal, rice and pasta are going to break down more quickly into glucose, which is fine at a meal where they are combined with protein or healthy fat. Other commonly consumed high carbohydrate foods include bagels, crackers, chips, rice cakes and potatoes. Bananas are higher glycemic than other fruits because they are more starchy and do not contain much fiber. Specific nutrients that lower the GI of a food include protein, fat and fiber.
Protein
Foods high in protein are low glycemic. This includes all meat proteins, soy, eggs and dairy products such as milk, yogurt, cheese and cottage cheese. Lean sources of protein are preferred as they will have less of an impact on cholesterol and triglyceride levels in the blood. Nutrition bars with an adequate amount of protein are low glycemic, as are protein shakes and smoothies.
Fat
Fat is the slowest nutrient to affect blood glucose levels. Choosing foods with the right type of fat can assist with glucose control while also providing benefits such as decreased cholesterol. Foods that are low-glycemic and contain healthy fat include nuts, seeds, avocado, peanut or almond butter and fatty fish. Other fatty foods will be low glycemic but may have a negative impact on cholesterol and therefore should be eaten in moderation. These include cheese, hazelnut spread and chocolate-covered peanuts or almonds.
Fiber
Fiber also slows the breakdown of glucose, but not all "high fiber" foods have enough to balance out the carbohydrate. Soluble fiber has more of a controlling effect on glucose than insoluble fiber, which often is processed and can be quickly digested. This is why whole-meal bread and white bread have similar GI values, as do brown rice and white rice. Basmaati or Doongara rice is lower glycemic, but still would be better consumed with a protein source such as beans or lentils to help control the breakdown of glucose. Foods high in soluble fiber such as oats, apples and legumes are low glycemic.
Low Glycemic Snacks
Eating a low GI food at a meal will help to balance the nutrients and keep the overall impact on glucose low. Snacks are often consumed in isolation however, and the GI value can be a good indication of which snacks can provide a steady release of energy. Low GI snacks include low fat cheese, low fat yogurt, edamame, almonds, walnuts, cashew or pistachios. Any fruit with skin will have a low GI value, such as apples, pears and plums. Examples of combination snacks that are low glycemic include a banana and peanut butter, a half bagel with cream cheese, granola and yogurt or nuts mixed with dried fruit.
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