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Should You Worry About High Glycemic Index Foods?

Evaluating foods solely based on their Glycemic Index (GI) can be misleading and does not provide a complete picture of their health impact. Here’s a more nuanced look at why this is the case and how to better evaluate foods for a healthy diet and we will help you understand this concept using coke and watermelon as examples.

Understanding Glycemic Index (GI)

The Glycemic Index measures how quickly a carbohydrate-containing food raises blood glucose levels. Foods are rated on a scale from 0 to 100, with higher values indicating a faster increase in blood glucose. While the GI can be useful for understanding how different foods affect blood sugar levels, it is only one part of the picture.

It is grouped as high, medium and low glycemic index foods –
1. Low GI Foods – 1 to 55
2. Medium/moderate GI Foods – 55 to 69
3. High GI Foods – 70 and higher

Factors to Consider Beyond GI

  1. Glycemic Load (GL):
    • Glycemic Load takes into account the quantity of carbohydrates in a serving of food, providing a more accurate representation of its impact on blood sugar. GL is calculated by multiplying the GI by the carbohydrate content per serving and then dividing by 100.

Coke vs. Watermelon: A Comparison

  • GI Values:
    • Coke: GI of 63
    • Watermelon: GI of 72
  • Carbohydrate Content:
    • 250 ml of Coke contains about 27g of carbs.
    • 250g of watermelon contains about 20g of carbs.
  • Glycemic Load:
    • coke – (63 x 27)/100 = 17
    • watermelon – (72 x 20)/100 = 14

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Glycemic Load Ranges:

  • low GL – 10 or less
  • medium GL – 11-19
  • high GL – 20 or more

Given this information:

  • Despite watermelon having a higher GI, the actual impact on blood glucose (glycemic load) might be lower due to its lower carbohydrate content compared to Coke when similar serving is compared.
  1. Nutrient Density:
    • Nutrient density refers to the amount of vitamins, minerals, and other beneficial nutrients per calorie of food. Watermelon, despite its higher GI, has some b vitamins, some minerals, antioxidants, and hydration due to its high water content. Coke, on the other hand, only has sugar.
  2. Overall Macronutrient Balance:
    • Evaluating the balance of carbohydrates, proteins, and fats in a meal is crucial. A high-GI food can have a different impact on blood sugar when consumed with protein, fat, or fiber, which can slow down the absorption of glucose and moderate blood sugar spikes. Meaning, say if you combine 2 whole eggs with both, which is a source of protein and fat, the release of glucose in the blood might be slower. In other words, the impact of high-GI foods can be mitigated by consuming them as part of a balanced meal that includes fiber, protein, and healthy fats, which can lower the overall glycemic response.
  3. Portion Size:
    • The quantity of food consumed significantly affects its impact on blood sugar. Even high-GI foods can be consumed in moderation as part of a balanced diet.
  4. Individual Variation:
    • People’s responses to carbohydrates can vary widely based on factors such as age, activity level, health status, and individual insulin sensitivity.

Practical Considerations for a Healthy Diet

So, instead of worrying about high glycemic index foods, focus on eating sufficient calories (around maintenance), eat sufficient protein (1.2-2 g/kg of bodyweight), staying active and hydrated, exercising regularly, eating mostly whole foods (this will have some fiber along).

Conclusion

While the Glycemic Index can provide useful information about how foods affect blood sugar, it should not be the sole factor in determining the healthiness of a food. Evaluating foods based on their nutrient density, Glycemic Load, macronutrient composition, and portion size offers a more comprehensive approach to healthy eating. High-GI foods can be included in a balanced diet when consumed in appropriate portions and as part of a meal that includes other macronutrients to balance their effects on blood sugar.

Research References

  1. Jenkins, D. J., Wolever, T. M., Taylor, R. H., et al. (1981). Glycemic index of foods: a physiological basis for carbohydrate exchange. American Journal of Clinical Nutrition, 34(3), 362-366.
    • This foundational study introduced the concept of the glycemic index.
  2. Augustin, L. S., Franceschi, S., Jenkins, D. J., et al. (2002). Glycemic index in chronic disease: a review. European Journal of Clinical Nutrition, 56(11), 1049-1071.
    • This review discusses the role of GI in the context of chronic diseases.
  3. Barclay, A. W., Petocz, P., McMillan-Price, J., et al. (2008). Glycemic index, glycemic load, and chronic disease risk—a meta-analysis of observational studies. American Journal of Clinical Nutrition, 87(3), 627-637.
    • A meta-analysis examining the relationship between GI, GL, and chronic disease risk.
  4. Venn, B. J., & Green, T. J. (2007). Glycemic index and glycemic load: measurement issues and their effect on diet–disease relationships. European Journal of Clinical Nutrition, 61(S1), S122-S131.
    • This paper highlights the challenges and considerations in using GI and GL to assess diet-disease relationships.

Glucose Spike & Fat Storage Is A Myth?

The relationship between glucose spikes from food consumption and body fat storage is often oversimplified in online discussions. Here’s a detailed explanation to clarify the confusion:

The Basics of Glucose and Fat Storage

1. Glucose and Insulin:

  • When you eat carbohydrates, they are broken down into glucose, which enters the bloodstream.
  • In response to rising blood glucose levels, the pancreas releases insulin, a hormone that helps cells absorb glucose for energy or storage.
  • Insulin also signals the liver to store glucose as glycogen and helps convert excess glucose into fat for long-term storage.

2. Energy Balance:

  • Energy balance is the fundamental principle of weight management. It’s the balance between calories consumed (through food and drink) and calories expended (through basal metabolic rate, physical activity, and digestion).
  • If you consume more calories than you expend, the excess energy is stored in the body, often as fat.
  • Conversely, if you expend more calories than you consume, your body will utilize stored energy, leading to fat loss.

Myths and Misunderstandings

  • Myth: Foods Causing Glucose Spikes Directly Lead to Fat Storage:
    • Reality: While high-glycemic foods (those that cause quick spikes in blood glucose) can lead to more insulin release, this doesn’t automatically mean these foods cause more fat storage if overall calorie intake is balanced. The body’s primary driver of fat storage is excess caloric intake, not just insulin spikes.
  • Myth: Energy Balance Doesn’t Matter:
    • Reality: Energy balance is crucial. Overeating any macronutrient (carbohydrates, fats, or proteins) can lead to weight gain if it results in a calorie surplus. The source of calories can influence how easily you may overeat (due to factors like satiety and nutrient density), but energy balance is the ultimate determinant of weight change.

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The Role of Glycemic Response

1. High-Glycemic Foods and Appetite:

  • High-glycemic foods can cause rapid spikes and drops in blood sugar, which might lead to increased hunger and overeating, potentially resulting in a calorie surplus.
  • Managing blood sugar levels can help with appetite control and may indirectly aid in maintaining a healthy weight by reducing the likelihood of overeating.

2. Insulin and Fat Storage:

  • Insulin facilitates fat storage, but it also supports muscle growth and overall energy regulation. Simply spiking insulin doesn’t inherently cause fat gain; it’s the excess calories that are stored as fat.
  • Insulin resistance, often a result of chronic high insulin levels, can contribute to metabolic issues and weight gain, but it’s a complex process influenced by many factors, including diet, physical activity, and genetics.

Practical Considerations

1. Diet Composition:

  • Focus on whole, nutrient-dense foods: These typically have a lower glycemic index and provide sustained energy without causing dramatic blood sugar spikes.
  • Balance macronutrients: Include a mix of carbohydrates, proteins, and fats to help maintain steady blood glucose levels and control appetite.

2. Overall Caloric Intake:

  • Monitor portion sizes and total caloric intake to ensure you are not consuming more energy than you are expending.
  • Physical activity: Regular exercise helps manage blood glucose levels, improve insulin sensitivity, and support overall energy expenditure.

Conclusion

While glucose spikes and insulin play a role in energy storage, they are not the sole factors determining fat gain. The principle of energy balance remains crucial: consuming more calories than you expend will lead to fat gain, regardless of the glycemic index of the foods consumed. Managing blood sugar levels can help with appetite control and overall health, but maintaining a balanced diet and regular physical activity are key for effective weight management.

Understanding these concepts can help you navigate the information you encounter online and make informed decisions about your diet and health.

Does L-Carnitine Work for Fat Loss?

L-Carnitine is often marketed as a fat-loss supplement, but the evidence supporting its effectiveness is limited and mixed.

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What is L-Carnitine?

L-Carnitine is a naturally occurring compound that helps with metabolism of fats or fat burning. In order for the fat to be used or burnt for energy there are two steps involved –

1. Mobilization of fat, meaning bring fatty acid out of adipose tissue into the blood, and
2. Oxidation of fat, meaning transporting fatty acid in the blood to any working cell’s mitochondria where it can be used/burned for energy.

L-carnitine helps with the transport of fatty acids into the mitochondria, where they are burned for energy. It acts like a transporter.

Mechanism of Action

L-Carnitine plays a role in the oxidation of long-chain fatty acids, facilitating their transport into the mitochondria, where they are used for energy production. This process is essential for energy metabolism, particularly during periods of fasting and exercise.

Scientific Evidence

1. Limited Impact on Fat Loss:

  • A meta-analysis published in the Obesity Reviews (2016) examined multiple studies and concluded that L-Carnitine supplementation had a small but statistically significant impact on weight loss. However, the effect size was minimal, and the clinical significance was questionable .

2. Exercise Performance:

  • Another study in the Journal of Physiology and Biochemistry (2014) found no significant difference in body composition between those who took L-Carnitine and those who did not .

Why is it Sold Despite Limited Evidence?

  1. Historical Belief and Marketing:
    • The initial interest in L-Carnitine for fat loss likely stems from its known role in fat metabolism. The idea that increasing its availability in the body could enhance fat oxidation and promote weight loss seemed logical and appealing.
    • Supplement companies have capitalized on this basic biochemistry knowledge, marketing L-Carnitine as a fat-burning supplement despite the lack of strong evidence.
  2. Placebo Effect:
    • Some users may experience a placebo effect, where they believe the supplement is working, leading to behavioral changes that contribute to weight loss, such as increased exercise and better diet adherence.
  3. Confounding Factors:
    • Many studies on L-Carnitine are not controlled for other variables such as diet, exercise, and lifestyle, making it difficult to isolate the effects of the supplement itself.

What Happens Inside the Body?

  1. Normal Physiology:
    • L-Carnitine is synthesized in the liver and kidneys from amino acids lysine and methionine. It is stored primarily in the muscles, heart, and brain.
    • During exercise, fatty acids are mobilized from fat stores and transported into the mitochondria by L-Carnitine for oxidation and energy production.
  2. Supplementation:
    • When consumed as a supplement, L-Carnitine is absorbed in the intestines and transported to tissues via the bloodstream. The body regulates its levels, and excess amounts are excreted in urine.

Why Doesn’t It Work for Fat Loss?

  1. Sufficient Levels in the Body:
    • Most people, especially those with a balanced diet, have sufficient L-Carnitine levels. Supplementing beyond these levels does not necessarily enhance fat metabolism.
    • The rate-limiting step in fatty acid oxidation is not L-Carnitine availability but rather the complex regulation of multiple metabolic pathways and enzymes.
  2. Energy Balance:
    • Fat loss ultimately depends on maintaining a caloric deficit. Simply increasing L-Carnitine levels without addressing overall diet and exercise will not lead to significant fat loss.
  3. Lack of Significant Impact:
    • As mentioned earlier, the impact of L-Carnitine supplementation on fat loss is minimal at best. Studies often show little to no significant difference in body composition changes between those taking the supplement and those not taking it.

Conclusion

While L-Carnitine plays a critical role in fat metabolism, supplementing with it has not been shown to significantly enhance fat loss in humans. The persistent belief in its effectiveness is largely due to its theoretical benefits, effective marketing strategies, and the appeal of a simple solution to a complex problem. For meaningful fat loss, a combination of dietary management, regular exercise, and lifestyle changes remains the most effective approach.

References

  1. Pooyandjoo, M., Nouhi, M., Shab-Bidar, S., Djafarian, K., & Olyaeemanesh, A. (2016). The effect of (L-)carnitine on weight loss in adults: a systematic review and meta-analysis of randomized controlled trials. Obesity Reviews, 17(10), 970-976.
  2. Villani, R. G., Gannon, J., Self, M., & Rich, P. A. (2000). L-Carnitine supplementation combined with aerobic training does not promote weight loss in moderately obese women. International Journal of Sport Nutrition and Exercise Metabolism, 10(2), 199-207.
  3. Wall, B. T., Stephens, F. B., Constantin-Teodosiu, D., Marimuthu, K., Macdonald, I. A., & Greenhaff, P. L. (2011). Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. The Journal of Physiology, 589(Pt 4), 963-973.
  4. Mingrone, G., Greco, A. V., Capristo, E., Benedetti, G., De Gaetano, A., & Gasbarrini, G. (1999). L-carnitine improves glucose disposal in type 2 diabetic patients. Journal of the American College of Nutrition, 18(1), 77-82.