Nutritionists used to say that a carb is a carb is a carb. Now that they understand the glycemic index they know that's not true.
They also used to say that a calorie is a calorie is a calorie. But now we have evidence that this isn't true either.
It depends whether the calorie is a solid or a liquid one. A new study demonstrates that when we take our food in liquid form rather than in a solid one, we consume more calories that day.
When we drink our beverages like soda and juice and particularly smoothies, they do satisfy our thirst. But they don't satisfy our hunger. So the calories from drinks just add on to the food calories we take in to our bodies.
The new study validates the little-noticed earlier work carried out in the lab of obesity researcher Barbara Rolls, which came to a similar conclusion. "Calorie intake increased significantly when people drank a beverage containing 150 calories with lunch, compared to when they had a calorie-free beverage."
Dr. Rolls reported this finding in her book The Volumetrics Eating Plan (HarperCollins, 2005). Thanks to correspondent Pam Cobo for recommending the book to me. It also has more excellent recipes than practically any book I have read lately. It is so good that I have already ordered her earlier book, Volumetrics: Feel Full on Fewer Calories (HarperCollins, 2000).
Personally, the only beverages - except for an occasional nip of single malt Scotch whiskey - that I drink are water, sugar-free lemonade, tea, and coffee, all straight up. So this research won't change what I drink.
But the calories in beverages account for one-fifth of the total American calorie intake, according to the August issue of the Mayo Clinic Health Letter. Sweetened sodas and fruit-flavored drinks are the main sources of those calories.
The reason that our bodies fail to recognize the calories in our drinks probably lies in our genes. For almost all of human history the only beverage our ancestors ever drank was water, which among its many advantages is free of any calories. Chalk up another reason to drink water.