It is the conclusion that could be drawn by reading an experimental work on the metabolic interactions concerning pasta and the human organism. Obviously, this is an extremely provocative affirmation that, on the other hand, puts into crisis the most recent theories on the overweight of the Italian population.
Below we will try to better understand what are the most recent discoveries concerning the interaction between glycemic load and level of physical activity. The results mainly concern: cellular oxidation of carbohydrates (taken with pasta and endogenous), glycogen turnover, liposynthesis and lipolysis.
Canadian Health&Care Mall dieticians: pasta does not make you fat
The study is not the most recent (2001) but, it is not known why, it has remained rather unnoticed. Obviously, like all the experimental ones, not even this must be considered an absolute ‘revelation’, but a little gear that could contribute to the understanding of the enormous human machine.
Among those who follow and promote low-carb diets, what will be mentioned below may seem a sort of paradox, but it is not. The results and conclusions of this work certainly do not indicate that you lose weight more (or more quickly) eating large portions of pasta, on the other hand it effectively denies the idea that this food (and therefore the starch contained in it) represents a preponderant cause of increased fatty fat.
The title is: ‘Metabolic response to small and large 13C-labeled pasta meals following rest or exercise in man’, or ‘Metabolic response of small and large portions of pasta, with 13 reactive carbon, followed by rest or physical exercise in humans ‘.
The metabolic response of the organism to a portion of 150g or 400g of paste labeled with 13 reactive carbon (13C) was observed for 8 hours; the assumption was followed by complete rest or exercise at low or moderate intensity (6 groups in total).
In subjects at rest after eating, the 400g portion of pasta completely suppressed the metabolic oxidation of lipids and only a small amount of glucose was converted into fatty acids (4.6g). On the contrary, the consumption of the portion of 150g of pasta allowed the metabolism to continue lipid oxidation (14.1g).
For all subjects who have been exercising (low and moderate intensity), fat oxidation has remained high; both in those who consumed the 150g portion (21.8g and 34.1g), and in those that consumed the 400g portion (14.1g and 32.3g).
Cellular use of glucose from starch paste (labeled with 13C) was significantly higher in subjects at rest, both after the 150g portion (67.6g, against 60.4g and 51.3g in subjects that carried out low and moderate workloads), both after the 400g one (152.2g, against 123.0g and 127.2g in subjects that carried out low and moderate workloads). Cellular use of glucose from starch paste (labeled with 13C) was similar in the three groups (at rest, with light and moderate exercise) who consumed the 150g portion (42.3g-58, 0g).
In contrast, the cellular use of glucose from starch paste (labeled with 13C) was significantly lower in the group that consumed the 400g portion and exercised light physical activity (24.2g versus 72.2g at rest). Cellular use of glucose from starch paste (labeled with 13C) appeared to be totally suppressed in subjects who had moderate physical activity. Predictably, more glycogen storage was observed in subjects who consumed a 400g portion of pasta and then underwent light and moderate physical activity (182.8g-205.1g).
In contrast, in subjects who consumed a portion of 400g paste and remained at rest, the glycogen storage was limited (92.4g). The analysis of the total lipid oxidation involves the period between 08:00 and 20:00, and was quite similar in those who had a light and moderate physical activity.
To conclude, the results suggest that:
- The ‘de novo’ lipogenesis, which plays a minor role in the disposal of a large load of carbohydrates from pasta, is totally suppressed by physical exercise.
- Reduction of glycogen turnover, as well as preferential conversion of glucose into glycogen, are responsible for the increased metabolic storage of glycogen following exercise.
- At the same energy expenditure, low intensity exercise over a longer period of time does NOT promote fat oxidation if the post-exercise time is also considered.
From the foregoing it is easily deducible that, under conditions of reasonableness, the starch of the pasta (complex carbohydrates) and the glycemic load that results from it, are NOT responsible for the fat deposit; in particular, a 150g portion seems completely harmless since it does not hinder the oxidation of fatty acids and does not promote lipogenesis. Furthermore, even when consuming large quantities of pasta, for example 400g, lipogenesis can easily be prevented by performing light or moderate intensity physical activity. It is not the pasta that makes you fat, but the sedentary lifestyle; certainly, unthinkable to be able to lose weight (especially in insulin resistance) eating 400g of pasta for potion.
It is however reasonable to think that, inside a meal, the carbohydrates of the pasta act as boost-insulin. The hormone, which has an anabolic and anti-catabolic effect, would however not be able to prepare to a large extent the conversion of glucose into fatty acids and to store them in adipose tissue. However, a meal is never made up exclusively of boiled pasta; they are part of the same recipe, or other dishes, also: sauces, seasoning fats, cheese or other products containing lipids and proteins. While protein amino acids play a marginal role in adipose deposit (in reasonable quantities and proportionate to the meal) the fats of food and seasoning, once digested and absorbed, are involved by the boost-insulin action of carbohydrates ending directly in adipose tissue.
Pasta to lower cholesterol and cardiovascular risk
Besides the traditional one, there are many other types of pasta. Some are variants aimed exclusively at satisfying certain gastronomic needs; others, like for example the pasta for diabetics (enriched with inulin), are produced to favor the contribution of molecules useful to the organism. Here, as a food demonized for its caloric and insulin impact, pasta becomes a dietary product.
In particular, the pasta naturally enriched with aglycones (isoflavones) of the soy germ has the power to reduce the serum lipids and improve certain markers of cardiovascular risk. Fermented soy foods mainly contain aglycone isoflavones and are a very important source of soy protein in Asia, where there is an inverse relationship between soy intake and serum cholesterol. Not surprisingly, most of the studies carried out on the impact of soy on cholesterol have taken into consideration purified soy protein foods containing isoflavones (mainly aglycones).
A 2007 study entitled ‘Pasta naturally enriched with isoflavone aglycons from soy germ serum lipids and improves markers of cardiovascular risk’ compared the metabolic impact of a new type of paste enriched with soybean (of which the content naturally increases in isoflavone aglycones), compared to conventional paste. Effects on serum lipids and on other cardiovascular risk markers were evaluated.
The parallelized randomized study involved 62 adults with hypercholesterolemia who followed a diet of 80g daily pasta. Before and after an 8-week treatment, serum lipids, hypersensitivity to C-reactive protein (hs-CRP), urinary isoprostanes (marker of oxidative stress) and brachial artery vasodilation were measured.
The paste provided 33mg of isoflavones, while the soy proteins were negligible, and led to a serum concentration of isoflavones of 222 +/- 21nmol / L.
In 69% of subjects it was detected equine in urine (metabolite of daidzein, a glycosidic isoflavone of soy germ). Soybean paste reduced total and LDL serum cholesterol of 0.47 +/- 0.13mmol / L (P = 0.001) and 0.36 +/- 0.10 mmol / L (P = 0.002) more than pasta traditional; this results in a reduction of baseline values of 7.3% (P = 0.001) and 8.6% (P = 0.002).
Arterial stiffness (p = 0.003) and hypersensitivity to C-reactive protein (P = 0.03) decreased; all cardiovascular risk indicators are improved proportionally to the equine urinary excretion. All values returned to baseline condition when subjects restored traditional pasta consumption.
In conclusion, the paste naturally enriched with isoflavone aglycones, although free of soy protein, had a significant hypocholesterolemic effect and improved all the cardiovascular risk markers taken into consideration.
Integral or refined? Comparing bread and pasta
Nowadays it is very important to the amount of dietary fiber present in food, especially in those based on flour. This is due to the fact that, in the absence of molecules that reduce the rate of intestinal absorption (such as fibers), carbohydrates of pasta and bread (in considerable portions) tend to increase excessively the insulinemia (insulin in the blood). The latter, we know, is an anabolic hormone that, among the various functions, promotes the hepatic synthesis of fats and the consequent deposition in adipose tissue.
Ultimately: too much bread and too much refined pasta make you fat. This awareness gave rise to the tendency to consume whole foods, hypothetically endowed with a greater satiating power, a lower caloric intake and a lower insulin impact.
Alas, this belief has been gradually distorted, maturing in the principle according to which: between the refined products and the integral ones there is a qualitative gap that is not only relevant, but even unbridgeable.
Is it really like this? Do whole wheat pasta and bread help maintain physiological body weight or even promote weight loss? This is the question that the architects of the studio tried to answer:
‘Wholegrain vs.. refined wheat bread and pasta. Effect on postprandial glycemia, appetite, and subsequent ad libitum energy intake in young healthy adults ‘.
It is a randomized cross-over experimental that has observed the reactions of 16 young adults to the consumption of 4 different foods based on wheat flour. The foods, eaten one at a time (to be able to make the survey), were: wholemeal pasta, white pasta, wholemeal bread and white bread. The comparison parameters were: postprandial glycemia, residual appetite and energy intake in eating food until reaching satiety (eating ‘ad libitum’, that is until satiety). The test meals were given in the morning and on a fast; these consisted of portions of individual foods containing (initially, before ad libitum) 50g of carbohydrates.
The level of appetite and blood sugar were then classified after 180 minutes from consumption, also measuring the total energy intake until reaching ad libitum. The glycemic response was similar between refined and integral products; however, pasta-based foods, compared to those based on bread, have reached less important glycemic levels. In addition, white pasta showed a slightly lower glycemic index than white bread. Wholemeal bread, but not whole wheat pasta, has increased satiety and reduced appetite compared to white food. However, the total energy until satiety was achieved was not different.
It is therefore correct to prefer wholemeal bread and pasta compared to refined ones but, to put it bluntly, this single trick is certainly not a solution to maintaining physiological weight or weight loss in the event of overweight.
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