Lisa,
We're actually finding common ground here - although we are far off the original posted question. I agree with you in the importance of adequate protein intake during a diet - IMO, the most critical elements to sparing lean tissue during a diet are sufficient protein and lifting heavy weights (to ensure that the body will try to maintain the muscle mass). (Don't make me dig into studies to support that assertion! Just my 0.02
)
Of course, being the irredeemable crank that I am, I will still point out some areas of disagreement with the study...first, I think focusing on the Protein/CHO ratio is misleading - I believe the important parameter is the ratio of protein to body weight (some use lean body mass, the concept is the same). Now, the Protein group in this study received 1.6g/kg of protein per day, the CHO group received 0.8g/kg of protein. For the protein group, this is about 0.7g/lb. By way of comparison, Lyle McDonald recommends 0.8g/lb for non-exercising individuals and 0.9g/lb for exercising individuals on a ketogenic diet. (After a pretty thorough review of the research, which I don't even want to try and duplicate - I'll take his word...) So the protein group is somewhere in the ballpark to experience protein sparing. So the comparison between groups is good, but I disagree with the parameter they chose to focus on...
Next, the protein intake of the CHO group was actually decreased from their baseline intake. Essentially, the CHO group had their protein and carb intakes slightly decreased (less than 10g), while the reduction in fat intake made up most of the caloric reduction. The protein group had the same reduction in fat intake, their protein increased 50g, and their carb intake cut by about 75g (mean values, so they won't "zero out"). Now, I strongly believe that any time you cut calories, you have to increase protein intake - so I like the result of the study..however, I would have liked it better (*and this criticism would have been removed*) IF they had kept the CHO groups protein intake constant from the baseline. As it is, you have one group with increased protein intake (associated with a protein-sparing effect), and then you cut the protein of the other group (which will likely increase protein losses) - VOILA, you attain the expected result....
Finally, do you notice that in the abstract they only quote the partitioning ratio of fat loss to lean loss? They don't represent the difference between total fat loss or total lean body mass loss as being significant...why? Because it wasn't! I hate to say it, (esp. because I do agree with the basic result) but they "cooked the books" here. Okay, there was a difference between the fat loss and the lean muscle loss between the two groups, but the difference wasn't significant. However, instead of stating *that*, they use the ratio of fat loss to lean loss...follow the bouncing ball. Both diets experienced a high percentage of fat loss as a percentage of weight loss (86% in the protein group and 80% in the CHO group)- -however the ratio makes the difference appear to be greater - because as you get up into high percentages, the denominator (lean loss) is going to drop more *relatively* than the numerator (fat loss). (86% is only 8% greater than 80%, but 20% is 43% greater than 14%). Why didn't they do the inverse ratio (lean loss to fat loss)?? Would the difference have been insignificant? Ah, the troubles with statistics....
Of course, I'm just being the crank...although the body composition methods still trouble me somewhat....