Eccesso proteico in grasso?

[°°sOmOja°°]

poco tempo fa ho letto questo articolo su t-nation
Protein Will Not Make You Fat
T NATION | Protein Will Not Make You Fat

naturalmente non considero questo sito alla stregua di pubmed, anzi, ma lo studio citato è coerente con la mia personale esperienza
da medico non considero più di tanto le discussioni basate su considerazioni personali ma preferisco fare riferimenti a studi scientifici e\o alle evidenze date dai fatti, con tutti i limiti presenti in entrambi i casi.
copio-incollo il paragrafo relativo allo studio:

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Enter One of the Most Tightly Controlled Studies of our Time

In 2012, George Bray and colleagues (5) sought to examine whether the level of dietary protein affected body composition, weight gain, and/or energy expenditure in subjects randomized to one of three hypercaloric diets: low protein (5%), normal protein (15%), or high protein (25%).
Once randomized, subjects were admitted to a metabolic ward and were force fed 140% (+1,000kcals/day) of their maintenance calorie needs for 8 weeks straight. Protein intakes averaged ~47g (0.68g/kg) for the low protein group and 140g (1.79g/kg) and 230g (3.0g/kg) for the normal and high protein groups, respectively.
Carbohydrate was kept constant between the groups (41-42%), with dietary fat ranging from 33% in the high protein group to 44% and 52% in the normal and low protein groups, respectively. Lastly, during the course of the 8-week overfeeding period, subjects' body composition was measured bi-weekly using dual x-ray absorptiometry (DXA, the "gold standard" for measuring body composition).
Results



At the end of the study, all subjects gained weight with near identical increases in body fat between the three groups. (In actuality, the higher protein groups actually gained slightly less body fat than the lower protein group. This, however, wasn't significant).

The group eating the low protein diet gained the least amount of weight (3.16 kg) with the normal and high protein groups gaining about twice as much weight (6.05 and 6.51 kg, respectively).
As you can see, the additional ~3 kg of body weight gained in the higher protein groups (15% and 25%) was shown to be due to an increase in lean body mass and not body fat. To quote the conclusions of the authors:
"Calories alone contributed to the increase in body fat. In contrast, protein contributed to changes in lean body mass, but not to the increase in body fat."
While we can't say for sure the exact composition of the lean mass that was gained, we can assuredly say that the extra protein was not primarily used for fat storage. My hunch is that the protein was converted to glucose (via gluconeogenesis) and stored subsequently as glycogen along with some accompanying water weight. Either way, it wasn't body fat.
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Se siete daccordo potremmo analizzare questo studio o la bibliografia allegata all'articolo, o meglio ancora altri studi che affrontano il problema
cerchiamo però di non fare troppa filosofia perchè non ho una formazione classica

[°°sOmOja°°]

repetita iuvant, copio-incollo l'abstract preso da pubmed (trovo sia più esplicativo) e inserisco il link allo studio completo


Effect of dietary protein content on weight gain, energy expenditure, and body composition during overeating: a randomized controlled trial.
Bray GA, Smith SR, de Jonge L, Xie H, Rood J, Martin CK, Most M, Brock C, Mancuso S, Redman LM.
Source
Pennington Biomedical Research Center, 6400 Perkins Rd, Baton Rouge, LA 70808, USA. George.bray@pbrc.edu
Erratum in

• JAMA. 2012 Mar 14;307(10):1028.

Abstract

CONTEXT:
The role of diet composition in response to overeating and energy dissipation in humans is unclear.

OBJECTIVE:
To evaluate the effects of overconsumption of low, normal, and high protein diets on weight gain, energy expenditure, and body composition.

DESIGN, SETTING, AND PARTICIPANTS:
A single-blind, randomized controlled trial of 25 US healthy, weight-stable male and female volunteers, aged 18 to 35 years with a body mass index between 19 and 30. The first participant was admitted to the inpatient metabolic unit in June 2005 and the last in October 2007.

INTERVENTION:
After consuming a weight-stabilizing diet for 13 to 25 days, participants were randomized to diets containing 5% of energy from protein (low protein), 15% (normal protein), or 25% (high protein), which they were overfed during the last 8 weeks of their 10- to 12-week stay in the inpatient metabolic unit. Compared with energy intake during the weight stabilization period, the protein diets provided approximately 40% more energy intake, which corresponds to 954 kcal/d (95% CI, 884-1022 kcal/d).

MAIN OUTCOME MEASURES:
Body composition was measured by dual-energy x-ray absorptiometry biweekly, resting energy expenditure was measured weekly by ventilated hood, and total energy expenditure by doubly labeled water prior to the overeating and weight stabilization periods and at weeks 7 to 8.

RESULTS:
Overeating produced significantly less weight gain in the low protein diet group (3.16 kg; 95% CI, 1.88-4.44 kg) compared with the normal protein diet group (6.05 kg; 95% CI, 4.84-7.26 kg) or the high protein diet group (6.51 kg; 95% CI, 5.23-7.79 kg) (P = .002). Body fat increased similarly in all 3 protein diet groups and represented 50% to more than 90% of the excess stored calories. Resting energy expenditure, total energy expenditure, and body protein did not increase during overfeeding with the low protein diet. In contrast, resting energy expenditure (normal protein diet: 160 kcal/d [95% CI, 102-218 kcal/d]; high protein diet: 227 kcal/d [95% CI, 165-289 kcal/d]) and body protein (lean body mass) (normal protein diet: 2.87 kg [95% CI, 2.11-3.62 kg]; high protein diet: 3.18 kg [95% CI, 2.37-3.98 kg]) increased significantly with the normal and high protein diets.

CONCLUSIONS:
Among persons living in a controlled setting, calories alone account for the increase in fat; protein affected energy expenditure and storage of lean body mass, but not body fat storage.

STUDIO COMPLETO:
Effect of Dietary Protein Content on Weight Gain, Energy Expenditure, and Body Composition During Overeating