Weight loss maintenance II

Although certainly the less glamorous part of the entire weight-loss picture, maintenance is undoubtedly the most important as well as the most difficult. It’s so important that MD and I wrote an entire book on it: Staying Power.
In our experience, protein consumption plays a major role in weight maintenance. A prepublication online article from the journal Appetite supports the use of added protein in maintenance diets (and in all phases of weight control).
The authors of the Appetite article in a previous paper showed that the addition of protein to a maintenance diet virtually eliminated the regain of fat over a three month study period.
The study subjects were all placed on a modified fasting regimen for a 4 week weight loss phase. After the 4 weeks the subjects were randomized into two groups for the 3 month maintenance phase of the study. One group had in addition to the maintenance fare about 50 grams of added protein in the form of a vanilla shake. In determining the overall protein intake of the groups, the researchers calculated that this additional protein raised the total protein from 15% of calories in the non-protein group to 18% of calories in the protein group, a small increase, which would imply that the protein group decreased their intake of other protein foods or the non-protein group increased their protein intake. The authors didn’t break down the macronutrient composition in their paper, which I see as a failure on the part of the people reviewing the manuscript.
After the 3 months, subjects in both groups had regained some weight, but not nearly back to their starting weight. The group receiving the additional protein regained only 50% of the weight that the group without the protein regained, but what’s remarkable is that none of the weight the protein group regained was fat: it was all lean body mass. The average waist circumference of the protein group actually continued to decrease during the 3 months of maintenance despite their regaining the small amount they did, whereas the waist circumferences of the non-protein group increased.
The extra protein lead to an increase in energy expenditure, which contributed to the lack of weight gain, and an increase in satiety that probably lead to a decrease in food consumption overall, but we don’t know for sure because the total calories and macronutrient composition of the diet were not included in the paper.
The authors conclude:

Additional protein consumption during weight maintenance after weight loss resulting in 18 vs 15 en% [percent energy] protein, resulted in a 50% lower body weight regain, only consisting of FFM [fat free mass, i.e., lean tissue] and related to increased satiety and decreased energy efficiency.

We can say from this study that more protein is better in terms of weight loss and maintenance, but we can’t tell anything from the data about differences in kinds of protein.
Is there a difference? Is one source of protein better than another?
In sifting through the scientific data the data, it appears so.
In the weight maintenance study the protein used in was calcium caseinate, a common, inexpensive protein often used in protein meal replacement supplements.
There are a number of protein sources available: animal protein, vegetable protein, and protein supplements made of whey, casein, and soy, or a combination.
A paper published in the American Journal of Clinical Nutrition in 2000 shows that animal protein (specifically, pork) produced a 3% higher energy expenditure over 24 hours than an equivalent amount of soy protein. That extra 3% energy expenditure would translate into a greater weight-loss or an easier time maintaining lost weight on the same number of calories.
Another interesting study published in the British Journal of Nutrition in 2003 shows that whey is vastly superior to casein (calcium caseinate) in a couple of ways. Subjects consuming 48 grams of whey as compared to an equal amount of casein ate significantly less 90 minutes later when presented with a buffet meal. This same whey preload lead to a 28% greater increase in blood amino acid levels over the next 3 hours and a substantially increased level of the appetite suppressing cholecystokinin.
If the weight maintenance study had been performed with the additional protein being either meat or whey instead of casein, the researchers would likely have seen an even greater difference.
The take home lesson if you’re trying to maintain is to increase your protein intake by 50 grams or so daily, preferably with either whey or meat.