What is the Glycemic Index (GI)? Essential Knowledge for Blood Sugar Management

Even with the same calorie count of carbohydrates, some cause weight gain while others are considered healthy. The key concept that explains this difference is the Glycemic Index (GI).

Definition

The Glycemic Index (GI) is a measure of how quickly a food raises blood sugar levels. Pure glucose is set at 100, and other foods are compared relatively.

Even with the same amount of carbohydrates, a high GI causes rapid blood sugar spikes, while a low GI leads to a slow and stable rise.

Understanding the Concept

When eating white bread (GI 75):

• Rapid blood sugar spike
• Sharp insulin release
• Blood sugar crash → Hunger, fatigue
• Fat storage promotion

When eating sweet potato (GI 44):

• Slow blood sugar rise
• Stable insulin release
• Long-lasting satiety
• Continuous energy

GI Classification

Low GI

Value: 55 or below Characteristics: Slow blood sugar rise, long-lasting fullness Effects: Weight management, diabetes prevention, sustained energy

Food Examples

• Brown rice (50)
• Sweet potato (44)
• Oats (55)
• Apple (39)
• Orange (40)
• Milk (30)
• Lentils (29)
• Chickpeas (10)
• Nuts (15-25)
• Most vegetables (10-30)

Medium GI

Value: 56-69 Characteristics: Moderate blood sugar rise Consumption: Before and after exercise or high activity

Food Examples

• White rice (64)
• Banana (62)
• Pineapple (66)
• Corn (60)
• Rye bread (65)
• Buckwheat noodles (59)
• Ice cream (57)

High GI

Value: 70 and above Characteristics: Rapid blood sugar rise, quick hunger Caution: Risk of obesity and diabetes with excessive consumption

Food Examples

• White bread (75)
• Bagel (72)
• Cornflakes (93)
• Potato (French fries 95, mashed potato 87)
• Watermelon (72)
• Rice crackers (91)
• Glucose (100)
• Beer (110)

GI vs GL (Glycemic Load)

GI Limitations

Problem: Doesn't consider actual food portion size

Example: Watermelon

• GI: 72 (high)
• But one slice (150g) contains only 11g of carbohydrates
• Actual blood sugar impact is minimal

GL (Glycemic Load)

Definition: Blood sugar impact considering actual portion size

Calculation Formula

GL = (GI × Carbohydrate amount(g)) ÷ 100

Classification

• Low GL: 10 or below (good)
• Medium GL: 11-19 (moderate)
• High GL: 20 and above (caution)

Comparative Example

Food	GI	Serving Size	Carbs(g)	GL	Evaluation
Watermelon	72	150g	11	8	Low GL (OK)
White bread	75	2 slices	30	23	High GL (Caution)
Cornflakes	93	1 cup	26	24	High GL (Caution)
Sweet potato	44	1 piece(150g)	27	12	Medium GL (Good)
Apple	39	1 piece	15	6	Low GL (Very Good)

Conclusion: Consider both GI and GL for accuracy.

Factors Affecting GI

1. Cooking Method

Cooking Time

• Pasta al dente (less cooked): GI 40
• Overcooked pasta: GI 60
• Conclusion: Less cooking means lower GI

Cooking Form

• Whole potato baked: GI 60
• Mashed potato: GI 87
• French fries: GI 95
• Conclusion: Smaller form increases GI

2. Processing Level

• Whole wheat (GI 45) < Whole wheat flour (GI 60) < White flour (GI 75)
• Brown rice (GI 50) < White rice (GI 64)
• Whole oats (GI 42) < Oat flour (GI 55)

Conclusion: More processing increases GI

3. Ripeness

• Unripe banana (GI 30) < Ripe banana (GI 62)
• Starch converts to sugar, raising GI

4. Fiber Content

• Dietary fiber slows digestion, lowering GI
• Whole grains > Refined grains
• Eating with vegetables reduces GI

5. Protein and Fat

Reduces GI when mixed

• Bread alone: GI 75
• Bread + Peanut butter (fat, protein): GI 55
• Bread + Cheese: GI 60

Reason: Fat and protein slow digestion

6. Acidity

• Adding vinegar or lemon juice reduces GI
• Why sushi rice has lower GI than regular rice

Low GI Diet Effects

1. Weight Loss

Mechanism

• Stable blood sugar → Reduced insulin resistance
• Long-lasting fullness → Prevents overeating
• Reduces fat storage

Research Results

• Average 2.3kg more weight loss in 12 weeks
• Significant abdominal fat reduction
• Minimal yo-yo effect

2. Diabetes Management

Type 2 Diabetes

• Reduces blood sugar spikes
• Decreases insulin requirements
• Improves HbA1c (glycated hemoglobin)

Diabetes Prevention

• 30% lower diabetes risk with low GI diet

3. Cardiovascular Health

• Reduces bad cholesterol (LDL)
• Increases good cholesterol (HDL)
• Decreases triglycerides
• Reduces heart disease risk

4. Sustained Energy

• Prevents blood sugar crashes → Reduces afternoon fatigue
• Maintains concentration
• Improves exercise endurance

5. Satiety

• Increases leptin hormone (fullness)
• Decreases ghrelin (appetite)
• Reduces snack cravings

6. Acne Improvement

• Insulin spikes increase sebum production
• 50% acne reduction with low GI diet (research)

Low GI Diet Implementation

1. Carbohydrate Replacement

High GI → Low GI

Existing (High GI)	Substitute (Low GI)
White rice	Brown rice, oat rice, barley rice
White bread	Whole wheat bread, rye bread
Cereal	Oatmeal
French fries	Baked sweet potato
White pasta	Whole wheat pasta
Rice noodles	Buckwheat noodles
White sugar	Stevia, erythritol

2. Add Protein and Fat

Slow blood sugar rise

Examples

• Bread only ❌ → Bread + avocado + eggs ✅
• Rice only ❌ → Rice + chicken breast + vegetables ✅
• Pasta only ❌ → Pasta + olive oil + chicken ✅

3. Vegetable Eating Order

Meal Order

1. Vegetables (fiber)
2. Protein (meat, fish)
3. Carbohydrates (rice, bread)

Effect: 20-30% GI reduction

4. Vinegar Usage

• Balsamic vinegar in salad
• Small amount of vinegar in rice (sushi style)
• Apple cider vinegar water before meals

Effect: Up to 30% GI reduction

5. Choose Whole Grains

• More fiber than refined grains
• Nutrient preservation
• Lower GI, higher satiety

6. Avoid Processed Foods

• Cookies, bread, cereal → High processing, high GI
• Choose natural foods
• Check labels: Avoid high sugar, syrup

7. Moderate Portion

• Overeating increases GL even with low GI
• 45-60g carbohydrates per meal is appropriate

Sample Low GI Daily Diet

Breakfast (Low GI)

Option 1: Oatmeal Bowl

• Oatmeal 50g (GI 55)
• Greek yogurt 100g (GI 14)
• Handful of blueberries (GI 25)
• 10 almonds (GI 15)
• 1 tbsp chia seeds

Option 2: Whole Wheat Sandwich

• 2 slices whole wheat bread (GI 51)
• 2 eggs (GI 0)
• Half an avocado (GI 15)
• Tomato, lettuce

Lunch (Low GI)

Brown Rice Bowl

• 1 bowl brown rice (GI 50)
• 150g chicken breast (GI 0)
• Broccoli, bell pepper, onion
• 1 tbsp olive oil
• Salad (vinegar dressing)

Eating Order

1. Salad first
2. Chicken breast and vegetables
3. Brown rice

Snack (Low GI)

• 1 apple + 1 tbsp almond butter (GI 39)
• Carrot sticks + hummus (GI 25)
• Greek yogurt + berries (GI 20)

Dinner (Low GI)

Salmon Quinoa Bowl

• 1 cup quinoa (GI 53)
• 150g grilled salmon (GI 0)
• Half a sweet potato (GI 44)
• Spinach, kale, cherry tomatoes
• Lemon dressing

GL Calculation

• Quinoa: (53 × 40g) ÷ 100 = 21 (Medium GL)
• Sweet potato: (44 × 27g) ÷ 100 = 12 (Medium GL)
• Vegetables, protein: Almost 0 GL
• Total GL: 33 (Below daily recommended 80) ✅

Precautions

Don't Focus Only on GI

Nutritional Balance is Key

• Ice cream is medium GI but not healthy
• Watermelon is high GI but nutrient-rich
• Consider overall diet quality

Consider Individual Differences

Same Food, Different Reactions

• Gut microbiome
• Insulin sensitivity
• Metabolic state
• Activity level

Solution: Use blood glucose meter to check personal response

Exceptions Before and After Exercise

Before Exercise (1-2 hours prior)

• Medium-low GI carbohydrates
• Example: Banana + almond butter

Immediately After Exercise (within 30 mins)

• High GI carbohydrates OK
• Quick glycogen replenishment
• Example: White rice + chicken breast, banana

Low Blood Sugar Caution

For diabetes patients on medication:

• Risk of low blood sugar when switching to low GI diet
• Consult doctor, transition slowly
• Essential blood sugar monitoring

Avoid Excessive Obsession

• Stress also raises blood sugar
• Consider social life
• 80% principle: Mostly low GI, occasional flexibility

Frequently Asked Questions

Q: Why are fruits low GI despite sugar content?

A: Fruit sugar is fructose, which is absorbed slowly due to accompanying dietary fiber. Apples, berries, oranges are below GI 40. However, fruit juices have removed fiber, increasing GI. Choose whole fruits over juice.

Q: How much weight can I lose with a low GI diet?

A: The low GI diet doesn't directly reduce calories but increases satiety, naturally reducing calorie intake. Research shows an average 2-5kg loss in 12 weeks, about 30% more effective than standard diets. Sustainability is key.

Q: Do I need a low GI diet if I don't have diabetes?

A: Yes, prevention effects are significant. Beyond diabetes prevention, benefits include weight management, cardiovascular health, sustained energy, acne improvement. Especially recommended for those with family history, obesity, metabolic syndrome.

Q: Must I completely avoid white rice?

A: Not necessary. You can lower GI through several methods:

• Mix with brown rice, barley (mixed grain rice)
• Cooled rice (increases resistant starch, reduces GI)
• Eat vegetables and protein first, rice last
• Add vinegar (sushi-style)
• Reduce portion, manage GL

Q: Why am I still hungry with low GI foods?

A: Several reasons:

1. Insufficient quantity: Low GI doesn't always mean enough calories
2. Protein deficiency: Carbs alone don't provide fullness
3. Dehydration: Drink enough water
4. Adaptation period: Body adjusting (takes 2-3 weeks)
5. Habit vs. Real Hunger: Stabilized blood sugar helps distinguish

Q: How can I check GI values?

A: Multiple methods:

1. GI Database: Sydney University GI Database (most authoritative)
2. Apps: GI Glycemic Index, Glucose Buddy
3. Books: "The Low GI Diet"
4. Principle: Less processed, whole grains, vegetables, protein are mostly low GI

If finding specifics is difficult, just follow the "unprocessed natural foods" principle.

Conclusion

Glycemic Index is more than just a diet—it's the foundation of lifelong health through nutrition. Choosing low GI carbohydrates stabilizes blood sugar, provides sustained energy, and maintains a healthy body.

You don't need to memorize every food's GI. Remember these basic principles:

• Whole grains > Refined grains
• Whole fruits > Fruit juices
• Lots of vegetables
• Combine with protein and fat
• Avoid processed foods

Start today: Replace white rice with brown rice, white bread with whole wheat. Small changes create significant health improvements!