GLYCAEMIC INDEX

Source: Hindu

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Context

• A Lancet paper provides compelling evidence linking high glycemic index (GI) diets with an increased risk of developing type 2 diabetes, especially among individuals with a higher Body Mass Index (BMI).
• The study spanned five continents and involved a large cohort of 127,594 adults aged 35–70 years without known diabetes.

Details

Glycemic Index and Glycemic Load

• GI ranks carbohydrate-containing foods based on their effect on blood glucose levels after consumption, while GL considers both the quality and quantity of carbohydrates in a serving.
• GI and GL were estimated based on the intake of seven categories of carbohydrate-containing foods using country-specific food frequency questionnaires.

Findings

• Association with Diabetes: A diet with a higher GI and GL was significantly associated with a higher risk of type 2 diabetes.
• Impact of BMI: The association between GI and diabetes was stronger among individuals with a higher BMI compared to those with a lower BMI.
• Incident Cases: After nearly 12 years of follow-up, 7,326 cases (5.7%) of type 2 diabetes occurred within the study population.

Implications

• Preventive Measures: Consuming low GI and low GL diets may help prevent the development of type 2 diabetes.
• Nutritional Choices: Making better food choices, particularly for individuals with a high BMI and family history of diabetes, can delay the onset of the disease.
• Public Health Importance: The findings underscore the importance of dietary interventions in mitigating the global burden of type 2 diabetes.

Examples of Low and High GI Foods

• Low GI Foods: Fruits, grains, lentils, non-starchy vegetables, legumes, dairy, brown rice.
• High GI Foods: Sugar, sugary drinks, white polished rice, potatoes, white bread.

About Glycemic Index (GI)

• The Glycemic Index (GI) is a numerical scale that ranks carbohydrates based on their effect on blood glucose levels after consumption.
• It measures how quickly a carbohydrate-containing food raises blood sugar levels compared to pure glucose, which has a GI value of 100.
• Foods with a high GI cause a rapid spike in blood sugar, while those with a low GI result in a slower, more gradual increase.

Determination of GI

• Testing Protocol: GI values are determined through standardized testing protocols in which participants consume a portion of the test food containing 50 grams of available carbohydrates after an overnight fast.
• Blood Glucose Monitoring: Blood glucose levels are then monitored over a period of two hours, and the area under the curve (AUC) is calculated to determine the food's GI value.
• Reference Food: Pure glucose or white bread is used as the reference food, with a GI value of 100.

GI Categories

• Low GI: Foods with a GI of 55 or less. They produce a gradual and steady increase in blood sugar levels.
• Medium GI: Foods with a GI between 56 and 69. They produce a moderate increase in blood sugar levels.
• High GI: Foods with a GI of 70 or higher. They cause a rapid spike in blood sugar levels.

Factors Influencing GI

• Type of Carbohydrate: Simple carbohydrates typically have a higher GI than complex carbohydrates due to their rapid digestion and absorption.
• Fiber Content: Foods high in fiber tend to have a lower GI because fiber slows down the digestion and absorption of carbohydrates.
• Food Processing: Processing methods such as milling and refining can increase a food's GI by removing fiber and other nutrients that slow digestion.
• Fat and Protein Content: Including fat and protein in a meal can lower its overall GI by slowing down digestion and the release of glucose into the bloodstream.

Benefits of Using GI

• Blood Sugar Control: Choosing foods with a low GI can help stabilize blood sugar levels and prevent spikes and crashes, particularly for individuals with diabetes.
• Weight Management: Low GI foods tend to be more filling and can help control appetite and promote weight loss.
• Improved Energy Levels: Consuming foods with a low to moderate GI can provide sustained energy levels throughout the day.

Limitations of GI

• Individual Variability: GI values may vary between individuals due to factors such as metabolism, insulin sensitivity, and the presence of other nutrients in a meal.
• Food Combinations: The GI of a meal can be influenced by factors such as portion size, cooking methods, and the presence of fat, protein, and fiber.
• Inaccuracy of GI Values: GI values are determined in controlled settings and may not always reflect real-world effects when foods are consumed as part of a mixed diet.

Application of GI

• Food Choices: Using GI values as a guide, individuals can make healthier food choices by selecting foods with a lower GI and limiting those with a higher GI.
• Meal Planning: Including a variety of low to medium GI foods in meals can help promote balanced blood sugar levels and overall health.
• Athletic Performance: Some athletes use GI principles to optimize carbohydrate intake before and during exercise to sustain energy levels and performance.

About Body Mass Index (BMI)

• Body Mass Index (BMI) is a simple numerical measure that is used to assess an individual's body weight relative to their height.
• It is widely used as a screening tool to identify potential health risks associated with being underweight, overweight, or obese.

Calculation of BMI

• Formula: BMI is calculated using the following formula: BMI = weight (kg) / height (m)^2
• Units: Weight is typically measured in kilograms (kg) and height in meters (m). However, weight can also be measured in pounds (lbs) and height in inches (in), in which case the formula is modified.

Interpretation of BMI Categories

• Underweight: BMI less than 18.5
• Normal Weight: BMI between 18.5 and 24.9
• Overweight: BMI between 25 and 29.9
• Obesity: BMI 30 or greater
• Classifications: Obesity is further classified into three categories: Class I (BMI 30-34.9), Class II (BMI 35-39.9), and Class III (BMI 40 or greater).

Significance of BMI Categories

• Underweight: May indicate malnutrition, eating disorders, or certain medical conditions.
• Normal Weight: Associated with lower health risks compared to other BMI categories.
• Overweight: May increase the risk of developing chronic diseases such as diabetes, heart disease, and hypertension.
• Obesity: Significantly increases the risk of various health problems, including type 2 diabetes, cardiovascular disease, stroke, certain cancers, and musculoskeletal disorders.

Limitations of BMI

• Does Not Account for Body Composition: BMI does not distinguish between fat mass and lean body mass. Therefore, individuals with high muscle mass may be classified as overweight or obese despite being physically fit.
• Does Not Consider Distribution of Fat: BMI does not account for the distribution of fat in the body. Excess abdominal fat, in particular, is associated with greater health risks.
• Does Not Address Individual Differences: BMI may not be appropriate for certain populations, such as athletes, older adults, and individuals with specific medical conditions.

Usefulness of BMI

• Screening Tool: BMI is a useful screening tool for identifying individuals at risk of weight-related health problems.
• Population Studies: BMI is commonly used in epidemiological studies to assess trends in obesity and related health outcomes at the population level.
• Clinical Assessment: In clinical settings, BMI is often used alongside other measures to assess an individual's overall health and risk of developing chronic diseases.

Additional Measures of Health

• Waist Circumference: Provides information about abdominal fat distribution, which is a better predictor of health risks than BMI alone.
• Body Composition Analysis: Techniques such as dual-energy X-ray absorptiometry (DEXA) and bioelectrical impedance analysis (BIA) can provide more accurate assessments of body composition, including fat mass and lean body mass.

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PRACTICE QUESTION Q.  While BMI has its limitations, it remains a valuable tool for assessing weight-related health risks and guiding interventions to improve public health. Comment. (150 Words)