Do fats make you fat? by R.Borgacci

Introduction

What are fats?

Fats, or rather lipids, are extremely important nutritional components for the organic balance of the "human machine"; although they are united in water insolubility, solubility in organic solvents and greasy consistency, between them the fats are extremely heterogeneous and differ in their molecular structure and biological function.

Fat functions

Referring to the entire category, lipids perform different functions; among them we remember:

1. Energetic (9 kcal / g)
2. Cellular structural (cholesterol and phospholipids are essential elements in the structure of cell membranes)
3. Nerve structural (constituent of myelin sheaths)
4. Bio-regulatory (hormonal and paraormonal precursors)
5. Vitamin solution (liposoluble vitamins: A, D, E and K)
6. Reserve (white and brown adipose tissue)
7. Essential, which concerns Essential Fatty Acids (AGE) or Essential Fatty Acides (EFA).

What are the most abundant fats in the diet?

The lipids of greatest nutritional interest are glycerides, as they constitute about 96-97% of dietary fats; not by chance are those most present also in the human body, since they represent the form of deposit accumulated in adipose tissue.

Glycerides can be formed from one, two or three chains of fatty acids (AG), bound to an alcohol - more precisely, glycerol - to form mono, di or triglycerides, respectively, or mixed molecules such as phospho-lipids. The molecular component of the glycerides that is used directly to produce ATP (energy) is the AG.

Food fats and body fat

Do fats make you fat?

After this brief introduction we will clarify the quantity and desirable lipid quality in the human diet; so let's get to the point: are fats fattening? The answer is not simple as it tends to be misleading but, in honor of the truth, one could say no . It is not fats that make you fat but rather caloric excess; however this does not mean that many fats do well. Let's go into more detail.

Too much fat or too many calories?

Overweight and obesity are pathologies mostly due to a positive caloric balance (result of the arithmetic operation "assumed energy - consumed energy"), which leads to an accumulation of Acetyl Coenzyme A in the cells - resulting from the beta oxidation of acids fats but also by dehydrogenation of glucidic pyruvate. This Acetyl-Coa should be used to produce energy (ATP); however, if made redundant, it can also be converted back into fatty acids to synthesize the triglycerides that fill the adipose tissue. This phenomenon is aggravated if the excess of Acetyl-CoA comes from a mixed surplus of fats and carbohydrates. Nevertheless, the indiscriminate excess of energy macronutrients also has a significant effect on the stimulation of insulin - the anabolic hormone which in this circumstance favors the adipose deposit. It has been shown that the insulin index of a meal does not necessarily coincide with the glycemic index of the same - that in a meal mixed with carbohydrates / fats it should be moderate.

In this sense, it is not too much fat that makes you fat, but too many calories. Regardless of the percentage of fat, if the energy supplied with the food is the same, different diets can give identical results on body weight. However, this does not mean that it is correct to exceed with lipids; in fact, too much fat in the diet can still be problematic.

Habits to lose

From a behavioral point of view, this is mainly due to dietary errors and poor physical movement; first of all, the abuse of high energy density foods .

Reaffirming that the excess of each of the 3 macronutrients (glucides, proteins and lipids), without exceptions but with some differences, leads to metabolic imbalances and induces weight gain. Too much high-protein dried meat or too many candy sugars, therefore, placed in a high-calorie context, favor weight gain as much as too much olive oil - obviously, with the same calories. It must however be admitted that, given their very high energy density, oily condiments are easily misused; this often leads to an unconscious excess of calories - two teaspoons of oil do not correspond to two rounds of cruet! The first habit to lose is therefore to eat too much, in this case too large portions and meals.

Secondly, motor activity. In this regard there would be much to say but we will limit ourselves to a few essential concepts. Feeding is a function of movement, not the other way around; in case of sedentary life it is however possible to remain thin. On the other hand, eating little becomes more complex to reach the recommended amount of nutrients such as vitamins, minerals, fiber and essential fatty acids. On the other hand, if you move a lot, your appetite increases a lot. In principle, those who travel little are more likely to gain weight; in parallel, it is not certain that moving a lot will be able to lose weight or maintain the normal weight.

The basic aerobic activities allow an excellent fat consumption potential, because they train the body in this direction. Those at very high intensity, even anaerobic, improve the consumption potential of carbohydrates - however essential for weight control. Let's say that a very busy cross-country skier could eat 5-10% more fat than normal - in relation to calories of course - without compromising performance.

How much fat do you eat?

Based on the Recommended Intake Levels of Nutrients for the Italian population (LARN), lipids should constitute 30% of the total energy portion in the growing individual and 25% in the adult, of which 1/3 are saturated and 2 / 3 unsaturated, also taking care to reach the AGE level but not exceeding 300 mg / day of exogenous cholesterol. For the same number of calories, even reaching 30%, an adult would not put on weight; a marathon runner, as we said above, could be handsome even reaching up to 35%.

The reader does not allow himself to be mislead by the wordings used in the presentation of the estimate; making the percentage calculation on the total caloric needs of the individual, non- energetic lipids are scrupulously and completely included, whose molecular functions are essential for the correct maintenance of physiological activities. In particular, the AGEs must be introduced in a quantity of 2.5% with respect to the total calories, respectively 2.0% with respect to omega 6 and 0.5% with reference to omega 3 (4: 1 ratio). We reiterate that the quantitative estimate of lipid requirements through energy distribution also guarantees the essential contribution of non-energetic or fundamental lipids for different metabolic purposes.

Too much fat cannot make you lose weight

Introducing a moderately higher lipid percentage reducing the carbohydrate or protein content does not significantly affect the energy balance and body composition. It is however mandatory to specify that, compared to proteins and carbohydrates, fats are the nutrients that have a greater potential for energy oxidation and are more concentrated ; that's why, comparing 2 isocaloric meals, one with a prevalence of lipid and one balanced:

it is deducible that the balanced one makes use of larger portions and is more satiating.

Too much fat can hurt your health

Fats, ketone bodies and nitrogen residues

At this point it would be logical to deduce that, in the diet, fats can replace carbohydrates; doing so could "train" the body to consume more lipids than glucose to the benefit of weight loss - muscle tissue enzymatic adaptation. But at what price?

Over the long term, drastic elimination / reduction of carbohydrates could cause several problems, including

• The gradual emptying of both the hepatic glycogen reserves - the latter essential to maintain blood glucose - and muscle.
• The increase of keto-acids, ammonium and urea in the blood.

The latter, if in excess, may favor some uncomfortable conditions including:

• A greater liver burden due to the increase of neoglucogenesis, therefore of the trans-aminase and relative urea cycle
• A greater renal load due to the hyperosmolarity of keto-acids and urea with a tendency to systemic dehydration
• Possible decompensated alteration of blood pH which, in association with hypoglycemia, in the long term can induce even serious central nervous complications
• Etc.

Metabolic impact of excess fat on lipemia and peroxidation

Finally, by translating the various dietary lipid regimens into nutrients, it is possible to observe two noteworthy aspects:

1. The abuse of animal foods containing saturated fatty acids, and of "artifact" products containing hydrogenated fatty acids, but above all in trans form, inevitably leads to an increase in endogenous LDL and total cholesterol
2. The abuse of plant foods containing unsaturated fatty acids - monounsaturated omega 9 and polyunsaturated omega 6 - induces a significant increase in the contribution of AGE linoleic acid but does not affect as effectively in the intake of AGE of the omega 3 group.

The lack of AGE can certainly be harmful. Nevertheless, some studies have hypothesized that even an excess, more precisely of omega 6, may induce undesirable effects. In fact, being a precursor of prostaglandins, excess arachidonic acid (data ascertained only at pharmacological doses) could be responsible for increasing the systemic inflammatory response. However, not all research shares this hypothesis. The risk of increased lipid peroxidation in the circulation is of greater importance; this phenomenon, which affects almost exclusively polyunsaturated fatty acids, is responsible for the increase in cardiovascular risk. So too many polyunsaturated fatty acids, instead of protecting blood vessels, could compromise them

It is therefore possible to define that:

dietary regimens with a high saturated fat content significantly worsen the blood lipid condition, while those with a high content of polyunsaturated fatty acids could negatively affect lipid peroxidation in the blood; moreover, it cannot be ruled out that very high doses of arachidonic acid may stimulate the production of pro-inflammatory molecules .

Conclusions

Conclusions on the metabolic impact of dietary fats

It is therefore possible to argue that at more or less balanced percentages "fats are not fattening". However, the prolonged excess of lipids and proteins in the diet to the detriment of the carbohydrate content - alteration necessary to maintain the isocaloric balance - can lead to an improvement in the oxidative efficiency of the fatty acids in the muscle cells; this aspect is not to be underestimated and associated with a meticulous qualitative selection of unsaturated fats to the detriment of the saturated - but without exaggerating, since the excess of polyunsaturated fats can be harmful - can find application, or give inspiration, in the treatment of some metabolic pathologies - especially those related to the abuse of refined carbohydrates in the diet, provided in the absence of renal and hepatic impairment. Despite this, the important and prolonged glucose discharge in the healthy and physically active individual has concrete, plausible and therefore non-negligible side effects.

deepening

Fat classification

Lipids are ternary elements composed of carbon (C), hydrogen (H) and oxygen (O) and can be classified according to their molecular complexity:

• Simple: Glycerides, Sterids and Waxes (esters formed by the link between an alcohol and fatty acids)
• Complexes: Phospholipids and Glycolipids (which also contain other molecules).

As anticipated above, the most significant fats from a quantitative point of view are glycerides, more precisely the fatty acids they contain.

Fatty acids

Fatty acids are simple ternary compounds and appear as long carbon chains. They mainly have an energy function and, in glycerides, they are in reserve. However they are not all the same and, on the contrary, they can be differentiated in a quite relevant way. The essential fatty acids, which are very important from a metabolic point of view and which we will give a brief overview below, make a special exception

Types of fatty acids

The AGs differ in length - short, medium or long chain - and the type of links that characterize them. The saturates are devoid of double bonds, the monounsaturated have a double bond and the polyunsaturates possess two or more double bonds; mono and polyunsaturated are enclosed in the unsaturated group.

Double bonds determine its chemical-physical characteristics such as: consistency based on temperature - unsaturated liquids are at room temperature while saturates have a solid consistency - heat stability and smoke point - for foodstuffs - sensitivity to peroxidation, etc.

Essential Fatty Acids

Essential lipids, that is elements that the organism is not able to synthesize independently, are called Essential Fatty Acids (AGE) or Essential Fatty Acides (EFA). They appear as simple carbonaceous chains and possess both 2 or more double bonds (polyunsaturated AG); they are called:

1. Alpha linolenic acid, from the omega 3 series, contained more in bluefish and soybeans
2. Linoleic acid, from the omega 6 series, contained mostly in olive oil, sunflower, corn, grapeseed and soya and in good quantity in dried fruit.

The AGEs perform some very important functions such as:

• Nervous and ocular development
• Membrane fluidification
• Transduction of membrane signals
• Interactions between cells
• Precursors of pro and anti-inflammatory eicosanoids
• Influence the immune system, for the synthesis of prostaglandins
• Docosahexaenoic acid (DHA) improves the synthesis of nitric oxide, is anticoagulant and anti-aggregator
• The omega 3s generally reduce triglyceridemia and blood pressure if in excess
• AGEs positively influence cholesterolemia, usually by increasing the amount of HDL (High Density Lipoprotein - good cholesterol).

Other less obvious effects of omega 3 are: protective action on the nervous system in the third age, beneficial role in moderating depressive symptoms, etc.

The total contribution of AGE must constitute 2.5% of the total calories divided into:

• 0.5% omega 3 (or from 0.5 g to 1.5 g)
• 2.0% omega 6 (or from 4.0 g to 6.0 g).

Bibbliografia

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