Study Review: High carb vs. high protein vs. high fat diet.

I found an interesting study today that got me thinking about a few issues. The study tested the effects of high carb, protein, or fat diets effect on insulin resistant, obese women. To those who are fond of conventional diet wisdom, the results may come as a surprise.

The study found that a diet high in protein may be the best way to fight off type 2 diabetes or cardiovascular disease when compared to high fat or high carb diets. Not only did the high protein/fat diet reduce insulin sensitivity better than the high carb diet, it also was more effective in the parameters of weight loss, waist circumference, and triglycerides. Low density lipoprotein cholesterol decreased in the HP and HC diet but fluctuated up and down in the HF diet.

Anyone who follows paleo/primal dieting is probably saying to themselves "well duh."

But I feel we should look a little closer to figure out why the results came about they way they did.

Participants were prescribed their diets based on macronutrient composition rather than total energy intake. This makes it possible that the carbohydrate diet, being less satiating, encouraged over-feeding among it's participants. As many people know, all digested carbohydrates (glucose, or blood sugar) that do not get stored as glycogen in the muscles, liver, and brain, get stored as fat by insulin. That is why a diet high in grains and sugars makes losing weight difficult for the average Joe. Glycogen stores are fuel tanks for short or intense activity. Lifting heavy weights (2-3 sets of 5-6 rep max weight per 3-4 exercises) depletes glycogen stores, so does sprinting. Therefore, if your activity levels range from sedentary to moderate, chances are you don't need too many carbs day to day.

This may not be the whole picture though. There's the thermic effect of food (or TEF) that you might take into consideration.

To put it briefly, your body doesn't magically make your food disappear. It takes energy to digest and process the nutrients to make them available to your body. This is the thermic effect.  Each macronutrient has a different thermic effect however; dietary fat, for instance, is easy to digest whereas protein is much more difficult. This means that for every gram of protein you eat, you ingest four calories, yet you burn about .8 calories in the digestion of said gram of protein, this gives your protein (which is highly satiating) a total calorie balance of about 3.2 kcal per gram.

So let's re-cap. Essentially, protein is the most filling macro and has the least calories per gram. Also, it has the greatest effect on insulin resistance out of the three macros. It's effect on all parameters were positive and it has none of the unfortunate side-effects of high carbohydrate consumption.

Now one might look closely at the text and see that the high carbohydrate diet was also high in fiber. Fiber is great for satiety and it takes more energy to burn through than regular carbs alone. This could be a great argument against my hypothesis that the HC practitioners were possibly more prone to over-eating. However,  this only solidifies the idea that carbohydrates should be limited because if all grounds are made equal between them and the HP diet in terms of TEF or satiety, there's still something amiss because the results show a great difference between the two macros in terms of protecting against T2D and cardiovascular disease.

I'll go more into this in another post.