The glycemic load (GL) of food is a number that estimates how much the food will raise a person's blood glucose level after eating it. One unit of glycemic load approximates the effect of consuming one gram of glucose. Glycemic load accounts for how much carbohydrate is in the food and how much each gram of carbohydrate in the food raises blood glucose levels. Glycemic load is based on the glycemic index (GI), and is defined as the grams of available carbohydrate in the food times the food's GI and divided by 100.
Glycemic load estimates the impact of carbohydrate consumption using the glycemic index while taking into account the amount of carbohydrate that is consumed. GL is a GI-weighted measure of carbohydrate content. For instance, watermelon has a high GI, but a typical serving of watermelon does not contain much carbohydrate, so the glycemic load of eating it is low. Whereas glycemic index is defined for each type of food, glycemic load can be calculated for any size serving of a food, an entire meal, or an entire day's meals.
For one serving of a food, a GL greater than 20 is considered high, a GL of 11-19 is considered medium, and a GL of 10 or less is considered low. Foods that have a low GL in a typical serving size almost always have a low GI. Foods with an intermediate or high GL in a typical serving size range from a very low to very high GI.
One 2007 study has questioned the value of using glycemic load as a basis for weight-loss programmes. Das et al. conducted a study on 36 healthy, overweight adults, using a randomised test to measure the efficacy of two diets, one with a high glycemic load and one with a low GL. The study concluded that there is no statistically significant difference between the outcome of the two diets.
Glycemic load appears to be beneficial in dietary programs targeting metabolic syndrome, insulin resistance, and weight loss; studies have shown that sustained spikes in blood sugar and insulin levels may lead to increased diabetes risk. The Shanghai Women's Health Study concluded that women whose diets had the highest glycemic index were 21 percent more likely to develop type 2 diabetes than women whose diets had the lowest glycemic index. Similar findings were reported in the Black Women's Health Study. A diet program that manages the glycemic load aims to avoid sustained blood-sugar spikes and can help avoid onset of type 2 diabetes. For diabetics, glycemic load is a highly recommended tool for managing blood sugar.
Glycemic load of a serving of food can be calculated as its carbohydrate content measured in grams (g), multiplied by the food's GI, and divided by 100. For example, watermelon has a GI of 72. A 100-g serving of watermelon has 5 g of available carbohydrates (it contains a lot of water), making the calculation 5·72/100=3.6, so the GL is 3.6. A food with a GI of 100 and 10 g of available carbohydrates has a GL of 10 (10·100/100=10), while a food with 100 g of carbohydrate and a GI of just 10 also has a GL of 10 (100·10/100=10).
The GI was invented in 1981 by Dr Thomas Wolever and Dr David Jenkins at the University of Toronto and is a measure of how quickly a food containing 25 or 50 grams of carbohydrate raises blood-glucose levels. Because some foods typically have a low carbohydrate content, Harvard researchers created the GL, which takes into account the amount of carbohydrates in a given serving of a food and so provides a more useful measure.
List of foods and their glycemic load, per 100 g serving 
All numeric values provided in the table are approximate.
(% by weight)
|Glycemic Load||Insulin index|
|Baguette, white, plain||95 (high)||50||48.0||—|
|Banana, Mean of 10 studies||52 (low)–55.3±7 (low)||20||10–11.06±1.4||56.7±3.5|
|Carrots, mean of 4 studies||47 (low)||7.5||3.5||—|
|Corn tortilla||52 (low)||48||25.0||—|
|Potato, mean of 5 studies||50 (low)–98.7±24.5 (high)||18.6||9.3–18.3582±4.557||84.7±7.7|
|Rice, boiled white, mean of 12 studies||–77±10.5 (high)–83±13 (high)–93±11 (high)64±9 (medium)|| –79.9 –79.677.5|| –60.83±8.295 –66.317±10.387 –74.028±8.75649.6±6.975|| –55.3±8.4 –67±15 -67±1140±10|
See also 
- "Glycemic Load Defined". Glycemic Research Institute. Retrieved 8 February 2013.
- Das, Sai Krupa; et al. (April 2007). "Long-term effects of 2 energy-restricted diets differing in glycemic load on dietary adherence, body composition, and metabolism in CALERIE: a 1-y randomized controlled trial". American Journal of Clinical Nutrition 85 (4): 1023–1030. PMC 2920502. PMID 17413101. Retrieved 8 February 2013.
- Ludwig, Daniel S. (May 2002). "The glycemic index: physiological mechanisms relating to obesity, diabetes, and cardiovascular disease". Journal of the American Medical Association 287 (18): 2414–2423. doi:10.1001/jama.287.18.2414. PMID 11988062.
- Villegas, Raquel; Liu, Simin; Gao, Yu-Tang; Yang, Gong; Li, Honglan; Zheng, Wei; Shu, Xiao Ou (2007). "Prospective Study of Dietary Carbohydrates, Glycemic Index, Glycemic Load, and Incidence of Type 2 Diabetes Mellitus in Middle-aged Chinese Women". Archives of Internal Medicine 6167 (21): 2310–2316. doi:10.1001/archinte.167.21.2310. PMID 18039989. Retrieved 8 February 2013.
- Krishnan, Supriya; Rosenberg, Lynn; Singer, Martha; Hu, Frank B.; Djoussé, Luc; Cupples, L. Adrienne; Palmer, Julie R. (2007). "Glycemic Index, Glycemic Load, and Cereal Fiber Intake and Risk of Type 2 Diabetes in US Black Women". Archives of Internal Medicine 167 (21): 2304–2309. doi:10.1001/archinte.167.21.2304. PMID 18039988. Retrieved 8 February 2013.
- "Simple Steps to Preventing Diabetes". The Nutrition Source. Harvard School of Public Health. Retrieved 8 February 2013.
- "Glycemic Index Database". University of Sydney. Retrieved 8 February 2013.
- Holt, Susanne H. A.; Miller, Janette C. Brand; Petocz, Peter (November 1997). "An insulin index of foods: the insulin demand generated by 1000-kJ portions of common foods". The American Journal of Clinical Nutrition 66 (5): 1264–1276. PMID 9356547. Retrieved 8 February 2013. Lay summary – David Mendosa (14 October 2009).
Note: Glucose Score & Insulin Score multiplied by 0.7 for Glycemic index & Insulin index respectively.
- Calculation using data already tabulated and data from Holt, 1997.
- Miller, Janette Brand; Pang, Edna; Bramall, Lindsay (December 1992). "Rice: a high or low glycemic index food?". The American Journal of Clinical Nutrition 56 (6): 1034–1036. PMID 1442654. Retrieved 8 February 2013.
- Calculation based on Miller, 1992
- "International table of glycemic index and glycemic load values: 2002", American Journal of Clinical Nutrition
- Tree/freetext search-style database of Glycemic Index and Glycemic Load (same number of food items but also calculates totals according to FAO/WHO specifications).