Protéines « lentes », protéines « rapides »

Protein intake is the main factor of regulation of anabolism. Intrinsic composition of dietary protein, digestibility and speed of digestion are major factors of regulation. Lactoserum proteins are named “fast” because quickly free in stomach, and hydrolyzed in duodenum. On the contrary, casein proteins are named “slow” because slowly free in small bowel and slowly absorbed. Ingested alone, slow proteins are more efficient to stimulate anabolism. “Slow or speed” characteristic of proteins persist also in complete feeding. “Proteic gain” of feeding could be assessed with this new data.     

Comment évaluer les besoins énergétiques et protéiques du sujet obèse ?

The energy and protein needs of obese patients remain difficult to assess. Indeed, the change in body composition related to obesity with an increase of fat mass makes the use of real weight not adapted to assess these needs. In addition, the fat-free mass, which is the main determinant of resting energy expenditure and nitrogen needs must be taken into account. Indirect calorimetry is the reference method to assess the energy expenditure of obese subject, but the access remains nevertheless difficult. Therefore, some predictive formulas of resting energy expenditure can be used. The formulas of Harris and Benedict, Mifflin et al., Müller et al. appear to be more accurate in the obese subject, as the equation of Huang et al. using fat-free mass. In critically ill obese patients, their predictions are less reliable. In this context, the Harris and Benedict formula can be used with the adjusted weight and a correction factor of 1.3. In the case of mechanical ventilation, the modified Penn State formula is the most accurate. The daily energy needs of the obese can also be assessed empirically at 20–25 kcal/kg of adjusted weight. Protein needs are more complex to evaluate. In the absence of recommendation at this level, daily protein intakes of 1.0–1.1 g/kg of real weight or 2 g/kg of ideal weight in the absence or presence of injury, respectively, may be recommended.