Protein for Weight Loss

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Louise Hay

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For several years now, the use of more proteins in weight loss diets has been considered the elite expedient to optimize the results obtainable through traditional low-calorie diets.

However, as we will see below, if it is true that greater amounts of protein for weight loss can have a positive effect on the reduction of body fat, it is equally true that some parts of the body can be negatively influenced by excess protein, causing some small (or, in the long term, large) metabolic-functional imbalances.

What are

Proteins are energetic macronutrients that provide 4kcal / g; these are polymers (complex chains) of amino acids (aa) which, in addition to containing carbon (C), hydrogen (H) and oxygen (O), possess an amino group including nitrogen (N).

In nature, protein chains (also called more generically peptides) possess numerous biological functions and, as such, are characterized by extreme structural heterogeneity: primary (or simple), secondary (in α-helix or β-sheet ), tertiary ("ball") or quaternary (more balls "tangled" together).

Dietary proteins, taken in large quantities to lose weight at the expense of carbohydrates and lipids, are found in all Foods; however, the proteins of foods are extremely different from each other, since their amino acid composition varies according to the biological function in the food [organism or primary food source (milk)] in which they are found.

Proteins can therefore be classified into simple: protamines, histones, albumins, globulins, gluteline, prolamines, phosphoprotides and scleroprotids, and compounds (including hemoglobin, chlorophylls and opsins). This distinction between the various proteins, from the nutritional point of view, leaves the time it finds; what is most interesting from the food aspect is in fact what is called biological value (VB). This term of comparison is based on the quantitative estimate and on the relationship between the various amino acid monomers (aa essential and aa non-essential) within the protein; to result ad high VB, this ratio must be similar to the one that characterizes the various aa of human proteins or, alternatively, of the egg (for more details, see the article: "Biological value").

What Foods

The VB of the proteins taken to lose weight is a parameter that, in reality, should not be more than a simple quibble; this statement can be justified by contextualizing (objectively and scientifically) the importance of VB to the absolute quantity of dietary proteins introduced with the diet. As many readers will already know, this parameter estimates the presence of essential aa, or those that the human body DON'T is able to synthesize autonomously; on the other hand, the detail that often escapes the attention of those who prefer proteins for weight loss is that: by increasing the peptide absolute, therefore indiscriminately between peptides with high, medium and low VB, the risk of running into a deficiency is practically nil.

This very common misunderstanding is generated (and fomented) by disinformation in the chemical-food sector; that is, the idea that many have on the subject means a medium or low VB protein as a "poor or lacking in essential aa" polymer, but this is not the case. Mostly, these amino acid chains differ from human ones in the "percentage" (and not absolute!) Deficiency of one or more essential aa's which, fortunately, are normally present in proteins contained in other foods.

Deficiency of essential aa can only occur in a diet mono thematic and / or quantitatively insufficient. To conclude the broad premise, it is appropriate to dispel another urban legend (which echoes vigorously in body-building gyms), namely that proteins for weight loss and those for building muscle tissue must be obtained from foods of animal origin since the structural polymers of plants DON'T they are digestible by humans; it is a wrong concept as it is incomplete and misleading.

What must be taken into account, on the other hand, is that, in foods of vegetable origin, proteins are never pure; they are instead accompanied by considerable quantities of starch, which for its part has a significant impact on the caloric power of meals, and which therefore can compromise the breakdown of energy macronutrients.

Furthermore, vegetable proteins are often accompanied (if belonging to raw vegetables) with considerable quantities of dietary fiber; this fibrous component, DON'T digestible for humans, it binds some structural peptides of the food and can limit both digestion and absorption. However, in a balanced diet (which provides about 30g / day of dietary fiber), the risk of malabsorption is almost non-existent, except for pre-existing pathological conditions (hypochlorhydria, pancreatic enzyme deficiency, intestinal enzyme deficiency, etc.).

Furthermore, I remember how much the wording "vegetable proteins" is indifferent or approximate, since the proteins of legumes, cereals and potatoes, in addition to boasting a higher VB than those of vegetables, may possibly enjoy a lower quantity of fiber in the food and greater digestibility.

Last but not least, cooking; consuming a raw vegetable (which certainly makes use of greater quantities of thermolabile vitamins and mineral salts otherwise degraded or dispersed with heat or physical treatment) limits its digestibility, as well as cooking and some manipulations (peeling, cutting, mincing, blending , pesto, etc.) are able to promote it.

Having finally enlightened readers on the fact that proteins for weight loss (if taken in excess) can easily come from plant sources and not just animals, let's try to understand because it should be necessary to choose a similar strategy at the expense of nutritional balance.


A diet characterized by a quantity or percentage of protein intake higher than the norm is called high-protein or (loosely) protein (read the articles: "Protein diet for weight loss" - "Protein diet example for weight loss" - "High protein diet example").

The first reason that pushes a pseudo-professional or a user to undertake a strategy based on proteins for weight loss refers to the greater satiety they confer compared to carbohydrates and lipids. Leaving aside the physiology of the hormonal and nervous feed-backs that regulate the satiety mechanism (really numerous and complex, which deserve not only an article, but an entire treatise), some studies conducted at the University of Washington have gutted a considerable satiating potential of proteins compared to that resulting from sugars and lipids; it seems that assuming the same energy (kcal / 100g of product) from foods with a high protein content compared to other mainly lipid or glycidic foods, the perception of satiety occurs more easily and more quickly; in addition, a distinction should also be made between the various proteins.

A very recent study has brought to light an exceptional predisposition of fish proteins for weight loss; it seems that, in rats, these show a high capacity to stimulate the secretion of gastrointestinal mediators responsible for satiety, namely cholecystokinin (CCK) and glucagon peptide-1 (GPL-1). The result would therefore be a physiological improvement in the regulation of body weight thanks to greater satiety and less food intake.

Many also think that protein intake does not stimulate insulin production. It is obviously incorrect. We know that the most effective energy nutrient in this process is glucose, easily obtainable from dietary carbohydrates, but also proteins - and in particular certain amino acids that compose them - tend to increase insulin, not only for their neoglucogenetic capacity, but also directly - as well as, for example, certain fatty acids. The famous "insulin calm" is therefore to be considered a hoax - fortunately, I would add, given the importance of this anabolic, anti-catabolic and hypoglycemic hormone. Obviously, in the case of pathology or impaired glucose and insulin tolerance, the speech changes radically; however, despite what many think, a subject affected by glycemic alterations must not eliminate carbohydrates from the diet in favor of proteins and fats, but must keep them virtually constant in percentage terms (to ensure good oxidation capacity is maintained), exercising and losing weight - if necessary, therefore in most cases.

Finally, to complete the picture, we remind you that the use of greater quantities of proteins to lose weight relies on a further metabolic mechanism, namely the specific dynamic action of foods (ADS); this parameter, which can be decomposed into specific dynamic action of nutrients, measures the metabolic cost necessary to digest and metabolize energy molecules. Well, by virtue of the digestive commitment (especially gastric), of the transamination, deamination and urea cycle operations, proteins (or rather, the amino acids that compose them) constitute the most "demanding" molecules to manage, which is why , by themselves, they help to increase the body's energy consumption by promoting weight loss.

Useful info

All these aspects, of course, play an essential role in controlling the low-calorie diet - especially in the country. This clarification, which at a first analysis would not find any plausible explanation, is motivated by the high frequency and large portions of consumption referring to foods with greater load and glycemic index (and relative energy density) considered "typical national".

The average country, in fact, drags behind various eating habits which, if they fit perfectly half a century ago, today have to cope with a caloric expenditure equal to 50% of that of the period in question, inevitably causing a weight increase in the population. general. Pasta, bread and olive oil which, if used correctly, could be the key to a healthy and balanced diet, currently, in statistics, figure as the object of food abuse par excellence, transforming the true Mediterranean diet ( as a panacea for metabolic diseases and "holy grail" of the longest-lived populations in the world) in a distorted and potentially harmful diet.

Let's be clear, even by temporarily eliminating them from the diet and promoting the consumption of a greater amount of protein to lose weight, sooner or later, the user will again find himself having to deal with these products, which is why the "trendy" high-protein diet schemes offer results that - although very good in the immediate future - are mainly characterized by the yo-yo effect, due to the absence of dietary education in the therapy itself (which, if done well, guides the subject to a greater awareness of their nutritional needs ).


In a balanced diet, protein should make up 12% of the calories for one sedentary, and in any case never exceed about double for any subject, even if a sportsman or athlete; the latter value, which would make any academic of dietetics and nutrition "stand on end", is obviously to be considered as an upper limit of tolerance, and DON'T as a real parameter of equilibrium; on the other hand, we remind you that in strength disciplines, in which a conspicuous increase in muscle mass is involved, it is quite common to use estimates for calculating the peptide requirement that involve the use of protein coefficients minimi per kilo of body weight (physiological or real) equal to 1,5-1,7g / kg - even if those most used are 2,2-2,5 g / kg. In this article we will omit to further investigate the protein needs of the athlete, because it is too long and complex - and, to tell the truth, still unclear.

With regard to slimming diets, we are currently witnessing a real invasion of "disposable" diets, ie strategies mainly focused on the profit of the creator but not very respectful of the scientific standards underlying a correct nutritional distribution; these modes of accelerated weight loss are based on increasing proteins in order to lose weight more quickly and, according to the authors, losing as little muscle mass as possible.

Starting from the assumption that by increasing the protein in the diet to lose weight, to respect the concept of low calorie content, it is necessary to reduce the share of fats and, alas, also that of carbohydrates, the new "eating patterns" do not make themselves adaptable to sports nutrition, of the infant, of the pregnant woman, of the nurse of the elderly, of the nephropathic, of the liver disease, etc. By altering the nutritional breakdown of macro energy, the risk of:

  • Accumulation of ketone bodies - if the diet is of the ketogenic type (high fat, low carbohydrate and normal protein in absolute terms)
  • Dehydration
  • Overloading of the liver and kidneys due to continuous deamination, transamination, urea cycles and disposal of nitrogen groups
  • Worsening of the PRAL
  • Possible alteration of the ratio between saturated and unsaturated fatty acids
  • Excess of dietary cholesterol
  • Nervous system glucose deficiency - if the diet is low-carb
  • Excessive gastric strain
  • Alteration of the intestinal bacterial flora
  • Constipation.

Obviously, the most serious consequences are those initially asymptomatic, because they can be prolonged in the long term - liver and kidney overload. These consequences, which rarely they begin due to excess protein for weight loss (if not in mild acute cases) in the healthy subject, but are inexorably aggravated if pre-existing, should lead the reader to appropriate reflection.

The suffering of the organs responsible for digestion and disposal of waste can be seriously compromised alone through the sum of various risk factors, such as: drugs, doping, alcoholism, drug addiction, diet, etc. This does not mean that excess protein is one of the potential risk factors involved.

Therefore… why risk it? A correct and balanced diet, even if self-managed, is always the desirable solution in order to reduce overweight as an element that compromises the lifestyle and good general health.

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