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Are All Calories Equal?

Posted: July 20, 2012

When trying to lose or maintain weight, most people will decide a certain number of calories they will eat each day to reach their goal. Does it matter how much of these calories come from fat, protein, or carbohydrates? If 1600 calories daily is the amount you need to lose weight, should you lose the same amount of weight no matter what kind of diet you are on? This article will answer these questions and describe the results of a recent study published on this topic.

What does research suggest?

According to a study from Harvard recently published in the Journal of the American Medical Association, not all calories are equal and it is best to follow a low Glycemic Index diet.  The study included 21 subjects who initially lose 10-15% of their body weights.  Subjects were then placed on low fat, low Glycemic Index, or very low carbohydrate diets for four weeks each.

The study results showed that following a low Glycemic Index diet was the safest.  Following the low Glycemic Index diet resulted in burning about 150 more calories daily than the low fat diet.  The low fat diet caused two negative effects: an increase in triglyceride levels (a type of fat in the blood) and a decrease in HDL cholesterol levels (‘good’ cholesterol).  The very low carbohydrate diet resulted in burning about 300 more calories daily than when on the low fat diet, but raised cortisol and C-reactive protein levels, which are negative effects.  Cortisol is a stress hormone that may raise the risk for diabetes and cardiovascular disease when levels are high.  C-reactive protein is a measure of inflammation so it is best to keep levels low.

So… What is the Glycemic Index?

The Glycemic Index ranks foods from 0-100 according to how they affect the body’s blood sugar level.  Foods that are absorbed slowly and cause a modest raise in blood sugar are low on the Glycemic Index.  Foods that are absorbed quickly and cause a spike in blood sugar followed by a plunge below normal levels are higher on the Glycemic Index.  A glycemic index score up to 55 is low, between 56-69 is medium, and at least 70 is high.  In general, fruits, most vegetables, and whole grains are low on the index.  Refined grains and starchy vegetables are usually higher on the index.

The Glycemic Index of commonly eaten foods:

·         Low: peanuts (7), dark chocolate (23), wheat tortilla (30), skim milk (32), apple (39), pasta (46), brown rice (50), 100% whole grain bread (51), bran cereals (55)

·         Medium: ice cream (57), overcooked pasta (58), banana (62), cola (63), raisins (64)

·         High: sweet potato (70), whole wheat bread (71), bagel (72), white bread (73), sports drink (78), pretzels (83), white rice (89), cornflakes (93), baked potato (111)

What does this all mean?

There is no ‘quick fix’ for losing weight.  It is best to follow a diet high in fruits and vegetables and low in added sugars and solid fats.  A low Glycemic Index diet may seem complicated, but the main messages of the diet are similar to those endorsed by MyPlate and the Dietary Guidelines for Americans:

  • Choose whole grain products (whole grain bread) instead of refined grains (white bread)
  • Focus on fruits and vegetables
  • For best results, follow as part of a healthy lifestyle, including at least 30 minutes of exercise daily

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