Thanks for your comments and your kind words. It was great seeing you this weekend and I hope you enjoyed the weekend. I thought you raised some great questions for some of the speakers.
I did have a question about the concept of not "drinking my calories." In the studies you cited, a person starting a meal with a glass of juice wound up eating more total calories, and I assume the same logic would apply to a smoothie.
We have to seperate pure liquid calories from smoothies and calorie density from satiety to understand the differences.
Pure liquid calories, like juice or soda, tend to leave the stomach very quickly, often in around 5 minutes, depending on the temperature.
A smoothie, which is blended food, will stay in the stomach much longer and produce a higher level of satiety than juice, though not as much as if the food in the smoothie was eaten un-blended.
Yet the people who started the meal with a soup ate the least total calories. Both the soup and the juice are liquids. And some soups are put through a blender, so I am trying to understand the concept. Do I have to be careful at all with soups?
First, these were vegetable soups so while they had liquid, they were also chock full of vegetables. So, while the liquid part of the soup may pass through quickly, the vegetables do not. In addition, veggies tend to soak up some of the liquid when they are part of a soup, and some of the veggies break apart into the water, which both helped contribute to the satiety.
In one experiment, Dr Rolls compared several soups, all made from the same ingredients but served differently. All were a veggie soup made from the same amount of broth and vegetables. One was served as a regular veggie soup, one as a chunky veggie soup, and one as a puree, and they all had a similar effect on satiety.
Is the liquid state of the calories relevant?
No, if it is pure liquid calories like juice or soda or sweetened beverages like tea.
However, remember, blended and pureed calories are not really liquids in the same sense and would be slightly better than the pure liquid calories but never as good as the whole food.
You may want to review this recent study and my discussion on it. It is not in the DVD but is has been added to the lecture..viewtopic.php?f=22&t=15419
Is there any calorie density damage done by "liquifying" whole plant food into a soup by cooking?
No. The calorie density would be the same but it may not be as satiating as the fiber works best when in its whole form.
What if it was pureed with a blender?
See the above linked study. Pureed food has the same calorie density but not the same satiety. Even though the calorie density of applesauce is the same as apples, it is easier to over eat on the applesauce.
What precisely does it mean when you recommend that we not drink our calories. Is it only juices and smoothies etc. that we need to avoid for weight loss?
The problem is you are putting juices and smoothies in the same category and they are different. A smoothie is a blended food.
When I refer to liquid calories I am referring to juice, soda, sweetened tea, etc.
When weight is an issue, I recommend avoiding all liquid calories, which would be juices, soda's, an sweetened liquids.
In addition, it may be beneficial to avoid blended foods as they are easier to over consume them as their "satiety" is not as good as the foods in the whole form
You can do the simple experiment yourself to see the difference.
Compare the satiety of equal calories of baked potatoes to mashed potatoes.
Compare the satiety of whole apples to applesauce.
Compare the satiety of garbanzo beans to hummus.
Compare the satiety of a smoothie, to the same fruits eaten whole.
I hope that helps