Poor Carbohydrates or Poor Fat?

Once and for all, it would be useful to understand whether slimming diets, to be effective, should be low in fat or carbohydrate poor.

In fact, the diet that helps to reduce body weight is simply less energy-efficient than a normal diet. In view of the fact that both fat, carbohydrates and proteins provide calories, the slimming diet should limit all three macronutrients proportionally.

There are also quite important differences concerning the metabolic impact of the various molecules (also within the same chemical category).

Carbohydrates are generally considered to be the most useful for energy supply and are indispensable for some tissues that cannot use fats; on the other hand, they have a rather strong insulin stimulating effect (therefore also fattening). Obviously, this characteristic is emphasized by the general abuse of the population towards the foods that contain them (in Italy, especially pasta). It is also necessary to point out that, among the various types of carbohydrates, some are more stimulating (glucose and dextrins) and others less (frutrose and galactose or polymers that contain them); furthermore, molecular complexity (polymeric or monomeric polymer) also plays a very important role in the liberation of insulin.

The same applies to proteins and lipids. The former, which seem like real “chains”, perform many biological functions; once digested and absorbed, they vary their impact on the fattening hormone (insulin) according to the type of amino acids that compose them. Likewise, triglycerides differ according to the fatty acids they contain; these, in the human body, perform (from a quantitative point of view) mainly the task of energy reserve, filling the adipose tissue. Proteins and fats are less stressful than carbohydrates for insulin secretion even if, as far as lipids are concerned, they constitute a “ready to use” deposit substrate (from blood, directly in adipocytes).

NB. The use of amino acids and lipids for energy purposes, in the absence (or almost absence) of carbohydrates, results in the accumulation of toxic molecules called ketones. These, potentially harmful to tissues of the organism, must not be present in excessive quantities and/or for long periods. Their effect on the nervous system is anoressigenic, so their accumulation in the blood is sometimes deliberately induced.

An experimental work in 2013, entitled “Very-low-carbohydrate ketogenic diet VS low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials”, attempted to determine which nutritional strategy was the most suitable for slimming: low carbohydrate (chetogenic) or low fat content.

The meta-analysis sought to verify whether subjects who undertook a VLCKD (<50g carbohydrates per day), and subjects who faced a Low Fat Diet (LFD,?% of total energy) obtained and maintained slimming and reduction of cardiovascular risk factors in the long term.

In August 2012, from the bibliographic sources: MEDLINE, CENTRAL, ScienceDirect, Scopus, Lillà, SciELO, ClinicalTrials. gov and scientific literature databases, studies with desirable characteristics for the meta-analysis in question have been extrapolated (without discrimination of date and nationality). These requirements are: Randomisation and sample of adults who followed a VLCKD or LFD (with 12 months or more of follow-up).

The primary parameter of the study was the evaluation of body weight; secondary parameters were: TG (Triglycerides), HDL cholesterol (HDL-C), LDL cholesterol (LDL-C), systolic and diastolic pressure, blood glucose, insulinemia, HbA1c levels (glyc hemoglobin) and C-reactive protein.

In the overall analysis, five studies of thirteen have revealed significant results.

Subjects who followed a VLCKD showed a decrease in body weight (1415 subjects), a decrease in TG (1258 patients) and a decrease in diastolic pressure (1298 individuals); whereas an increase in HDL cholesterol (1257 patients) and LDL cholesterol (1255 individuals) occurred.

It has emerged that, in the long term, people with a VLCKD have achieved greater weight loss than those with LFD; ultimately, VLCKD can be considered a potential tool in the fight against obesity.

Given by hand, the ketogenic diet allows you to lose weight not only in the short but also in the long term; however, is it really the right choice to distort your diet to allow you to lose weight? Probably not.