Is it really necessary to eat all the food groups?

We will have probably heard many times: "Do not stop eating any of the food groups, all are necessary." A phrase that appeals to fear, that sounds like we're actually depriving your body of an essential macronutrient.

Needless to say this phrase used especially those who want to criticize the low or very low carbohydrate diets. They want to convey is that if we eat something bad carbohydrates we will, because we are eliminating one of the three major food groups (along with proteins and fats).

First, we should clarify that that there are three major food groups, also called macronutrients, is but one of our classification based on the chemical composition and the amount you usually eat. We could classify otherwise, subdividing the types of carbohydrates or fats, including micronutrients, or alcohol, and even water.

Secondly, there are only a macronutrient medically which can be dispensed completely without suffering any pathology almost immediately: carbohydrates. You can try to look at any book on medicine, but will not find it. But if we do not eat any fat or protein, we will fall ill within days.

Third, the foods that nature has given us for eons carbohydrates are vegetables and fruits. No more, until agriculture was first used extensively less than five thousand years ago. Most modern diets that restrict carbohydrates not relate to vegetables and fruits not. Why then has to be now need to eat cereals, pasta, bread or rice? Luckily, not all bad news. Agriculture and civilization if we have brought some carbohydrate foods that have proven to be healthy and have no undesirable side effects of the above: Legumes and whole foods, that is, the low glycemic index. Because the terminology of "simple carbohydrates or complex" to be heard often makes sense chemically but nutritionally it for very little. The glycemic index, which indicates the rate of absorption is the factor that really gives valuable information about your behavior on our digestive system. The smaller this value, the slower and less absorption peaks of glucose and insulin have in our bloodstream.

And finally, as I explain in the book "What the science says ... diet": Is there any scientific evidence that stop eating refined carbohydrates rapidly absorbed or unhealthy? No. And some that seem to indicate otherwise? Well enough ... This has been the theory, let's test:

Studies linking refined carbohydrates with diseases or disadvantages:

- Low-Carbohydrate-Diet Score and the Risk of Coronary Heart Disease in Women (2006)
- White rice consumption and risk of type 2 diabetes: meta-analysis and systematic review (2012)
- Carbohydrate nutrition is Associated With the 5-year incidence of chronic kidney disease (2011)
- Long-term effects of a lifestyle intervention on weight and cardiovascular risk factors in Individuals with type 2 diabetes mellitus

Studies finding health benefits for low-glycemic foods:

- Glycemic index and glycemic load are Associated With Some cardiovascular risk factors Participants Among the PREMIER study (2012).
- Dietary glycemic load and glycemic index and risk of coronary heart disease and stroke in Dutch men and women: the EPIC-MORGEN study (2011).
- Glycemic index, glycemic load, and chronic disease risk - a meta-analysis of observational studies (2008).

So when you play that all food groups are needed, remember that vegetables and fruits, even with legumes and whole foods from time to time, you can eat all the carbohydrates you need and the format in which your metabolism is designed to assimilate perfectly. The rest are at best optional. But not necessary.
The Weight of the Nation, online and with subtitles in Spanish
These are the links to the fashion documentary on obesity released in the US yesterday, "The Weight of the Nation" (The Weight of the Nation):

First part: Consequences
Part Two: Options
Part Three: Children in crisis
Part Four: Challenges

To see subtitles in Spanish, you have to move the mouse over the video and when you leave the control bar (bottom right) click on settings and activate the subtitles.

In short, I will write my comments and views on the documentary.

Update: It seems that the server HBO has collapsed, because there is no way to go fluid video. Also the four parts on YouTube, but in English without subtitles (except the first).