Date: December 13, 2007

Speaker's Name, Affiliation:

Margriet Westerterp-Plantenga
Maastricht University, Netherlands

Seminar Title: "Short- and long-term effects of different proteins on food intake"

Presiding Chair: Harry R. Kissileff, Ph.D.

Rapporteur: Kathleen L. Keller, Ph.D.

Attendees and their Affiliation:

Kathleen Keller	Columbia/Obesity Research Center
Harry Kissileff	Obesity Research Center
Tony Sclafani	Brooklyn College
Karen Ackroff	Brooklyn College
Joel Grinker	University of Michigan
Malki Miller	Brooklyn College
Rosalyne Tu	Teacher's College
Carol Maggio	NYORC
Joe Vasselli	NYORC
Yiying Zhery	NYORC
Eva Kovacs	Unilever
Allan Geleibter	St. Luke's
Michael Lowe	Drexel University

Summary: (Prepared by the Speaker)

Relatively high protein diets, i.e. diets that maintain the absolute number of grams of protein ingested as compared to before dieting, are a popular strategy for weight loss and weight maintenance. Research into multiple mechanisms regulating body weight has focused on the effects of different quantities and types of dietary protein. Satiety and energy expenditure are important in protein-enhanced weight loss and weight maintenance. Protein-induced satiety has been shown acutely, with single meals, with contents of 25% to 81% of energy from protein in general or from specific proteins, while subsequent energy intake reduction was significant.

Protein-induced satiety has been shown with high-protein ad libitum diets, lasting from one to six days, up to six months. Also significantly greater weight loss has been observed, in comparison with control.

Mechanisms explaining protein-induced satiety are nutrient specific, and consist mainly of synchronization with elevated amino acid concentrations.

Different proteins cause different nutrient related responses of (an)orexigenic hormones. Protein-induced satiety coincides with a relatively high GLP-1 release, stimulated by the carbohydrate content of the diet, PYY release, while ghrelin does not seem to be especially affected, and little information is available on CCK. Protein-induced satiety is related to protein-induced energy expenditure. Finally, protein-induced satiety appears to be of vital importance for weight loss and weight maintenance.

Discussion:

Q.Is there any difference between men and women with respect to protein requirements?
A. Yes, the % of protein is the same, but women require fewer absolute grams.

Q.Is the protein load on the kidney related to the absolute amount of the load or the concentration of protein in the plasma?
A. You will not have a higher concentration of protein in the plasma if you are on a relatively higher protein diet. You break this down into amino acids and they are rebuilt in the body into proteins, hormones, etc. It's the absolute amount of protein that is important for the kidneys.

Q.When you say that it takes less energy to gain the same amount of fat mass, compared to FFM, where does this excess energy go?
A. It is lost to thermogenesis. Amino acid metabolism results in greater losses as heat.

Q.The high protein regimen that you have participants follow, is it low in fat?
A. We do not know the composition of the diet that they follow, as we do not test that.

Q.Are they instructed to eat a certain amount of total energy?
A. During the weight maintenance phase, we give them an additional protein supplement, but otherwise do not give them specifics on energy intake.

Q.What is the supplement that you give them?
A. Calcium caseinate powder, to be dissolved in any type of liquid they wish.

Q.Did they find the powder/supplement sufficiently palatable?
A. Yes

Q.What did the control group get?
A. Nothing.

Q.Do you see any negative side effects (eg. nausea)?
A. Only that they think the high protein diet is too satiating.

Q.When did you take the satiety measurements (in what part of the daily regime)?
A. For thermogenesis, we took the measures early in the morning when they were fasted. The VAS were also assessed during the fasted state.

Q.So the effect on satiety that protein has seems like it is a long-term effect?
A. Yes, I will show you those results a little bit later.

Q.Did you also look at ghrelin levels on the carbohydrate diets?
A. We did not look at that.

Q.Are the bars on your graphs standard error bars? Why is it only significant at two places?
A. Yes, they are standard error bars. These were the two places that mattered for further decisions. It may have been significant at other places, but we did not test that.

Q.Do you think your data support the aminostatic theory?
A. Yes, I think so, but mathematical correlations with satiety and GLP-1 or with the amount of protein are not clear.

Q.Did you look at leptin levels in the high protein diets?
A. No, we didn't.

Q.Earlier, you showed that people are more satiated in the morning. Could that be attributed to the long-term amino acid curves?
A. Yes, it could be.

Q.Is whey considered a complete protein?
A. Whey, casein, and soy-protein are all complete proteins

Q.Did you see a difference in selective intake for proteins at lunch?
A. No, we did not allow a free-selection of foods at lunch.

Q. When you talk about the % changes in hunger, are you talking about 2 measures, and the difference between the two?
A. Yes.

Q.If the difference was not due to the tryptophan, why did gelatin and lactoalbumin differ in the satiety that resulted from them?
A. We think it might be the differences in the concentrations in some of the large neutral amino acids.

Q.Why didn't you report on levels of CCK?
A. We have done that in other studies, but the results have never been that clear. Also, for practical reasons (including the number of blood draws we were able to do), we opted not to include it.

Q.Is there any evidence that these effects (with respect to protein and satiety) decrease over time?
A. If people comply with the diets, the effects will not dissipate.

Q.With respect to compliance, it can be almost any type of new behavior. People resist making changes in their lifestyles, regardless of the type of change. However, it can also be due to the fact that the diets were making people nauseous or bloated. Do you have any sense which is the case in your data?
A. I do not think people were nauseous or had side effects indicative of too much overall protein, because the amount was not an increase in the actual amount of protein, it was only increased expressed as % of the diet.

Q.If you gave them a low calorie dessert that was tasty, but that would not provide a lot of calories, do you think that would improve their well-being?
A. That's a question for the food industry.

Q.Were your patients all obese?
A. They were overweight patients that had never dieted before.

Q.Do you see this as the same concept as "imbalanced protein diets?
A. Yes.

Q.What is the dropout rate for the high-protein diet?
A. Very little, and it's always the highest during the first week.

Q.Did you do a follow up after the experiment?
A. Yes, the high protein group had still lost more weight, half a year later.

Q.What do you think is the missing amino acid in the incomplete protein diet that results in a lowered effect on satiety and weight loss?
A. We think that Leucine may be an attractive candidate.