Popular Fad Diets: Do They Work?

Two thirds of American adults are classified as overweight and of that one third is classified as obese.  What do we plan to do about it?  Nothing.  But we want to be able to blame someone else.  We've all heard of those fad diets that claim you will lose 20% of your body weight in 2 weeks by doing nothing.  They sound pretty intriguing to most of you, don't they?  But do they work?  This week I will leap into the scientific depths of three fad diets out there today and try to make some sense out of them for you: The Low Glycemic Index Diet, The Low Carbohydrate Diet, and The High Calcium Diet.

The Low Glycemic Index Diet

First, I think I should define what the glycemic index truly is.  The glycemic index is a measure of the effects of carbohydrates on blood sugar levels.  Carbohydrates that break down quickly during digestion and release glucose into the bloodstream have a high glycemic index; carbohydrates that break down more slowly and release glucose more gradually into the bloodstream have a low glycemic index.  The concept was developed to assist individuals with diabetes better understand and manage the types of foods they eat and ultimately help control their blood sugar and insulin levels.

As a rule of thumb, the more simple sugars contained in a food, the higher the glycemic index of the food.  Foods such as candy, sugary drinks, white bread, and white rice cause a higher spike in blood sugar and therefore have a higher glycemic index.  Foods such as rolled oats, whole grain bread, and whole grain pasta cause a more gradual increase and decrease in blood sugar and therefore have a lower glycemic index.

Many individuals have attempted a low glycemic index diet as a way to reduce energy intake and promote weight loss.  It is thought of as a way to increase whole grains in the diet and feel fuller longer with the increase in fiber.  According to eight randomized controlled studies, there were no significant differences in energy intake or body weight after the consumption of a low glycemic index diet.

Strike one!!

The Low Carbohydrate Diet

Lately the push is low carb, low carb, low carb!  But what does a "low carb" diet actually mean?  And does it work?

There is no "universal" definition of a low carbohydrate diet.  Some general guidelines are:

• Consuming less than 50 grams of carbohydrates per day
• Consuming less than 10% of kilocalories from carbohydrates per day
• Kilocalorie/day breakdown = 10% from carbs, 25-35% from protein, 55-65% from fat

So, do they work?  The research has shown that consumption of either low carbohydrate diets or reduced kilocalorie diets both result in lower kilocalorie intake.  However, low carbohydrate diets resulted in greater body weight loss and fat loss in the first six months than the reduced kilocalorie diet.  After one year the differences between these diets are no longer significant.

Why does a low carbohydrate diet seem to work?  Well, these low carbohydrate diets are incredibly high in protein compared to a normal, balanced diet.  There seems to be a greater thermic effect of food with these high levels of protein (which means it takes more work for your body to break down a gram of protein than a gram of carbohyrate or fat, and therefore, your body ultimately burns more kilocalories breaking these down).  Also, protein promotes greater satiety, which means you will feel fuller longer. 

Secondly, the high amount of protein and fat in this diet promotes ketogenesis.  Ketogenesis is the generation of ketone bodies in your bloodstream.  Ketone bodies are produced as byproducts when fatty acids are broken down for energy.  Due to the lack of carbohydrates (which is the preferred fuel source for your cells), your body has to find something else to use for fuel.  Solution?  Fat!  These ketone bodies also seem to have a greater thermic effect of food and promote appetite suppression as well. 

 

Downsides?  The early, higher weight loss compared to the reduced kilocalorie diet could be just a decrease in body water, and the ultimate result (the unsignificant differences after one year) is probably linked to the inability to adhere to the diet.  Its hard to live with only 10% of your diet from carbs!!  Also, ketone bodies cause individuals to feel tired and run-down during the day and many report having less energy to do activities of daily living.

If you do decide to try a low carbohydrate diet, my recommendation would be to speak with an RD prior, just to make sure all the bases are covered.  It is easy to overlook essential vitamins and minerals when cutting out certain carbohydrates from your every day intake.

Ball one!!

The High Calcium Diet

We've all seen it.  That commercial with the incredibely skinny blonde woman, smiling and eating a carton of Dannon yogurt.  Then, the commentator announces that individuals who consume three servings of dairy per day have been proven to weigh less than those who don't.  And what do we know about dairy products?  Well, they contain a good amount of calcium per serving. 

But in healthy adults, how effective (in terms of weight loss and maintenance) is the high calcium diet?  Several studies report that total daily intakes of calcium below the recommended levels (1,000 mg/day for adults) are associated with increased body weight, body fat, body mass index, waist circumference and relative rise of obesity in adults.  HOWEVER, it is unclear if this is a result of poor overall diet, and not a direct result in low calcium intake.  More research in this area is needed.

Strike two!!

So, what is the take-home message about these fad diets?  We had one ball and two strikes.  The low glycemic index diet and the high calcium diets are definately proven to not make much of a difference in terms of weight loss.  The research proves it.  But the low carbohydrate diet?  As much as I hate to admit, the research proves that this might be beneficial in terms of rate of weight lost for the first 6 months of dieting. 

What would I recommend to individuals?  A reduced calorie intake with a balanced diet.  That has been proven effective over and over again.