DEAR DR. BLONZ: I have kept up with a group of my high school friends through social media. Back then, we went out for the same sports and all had comparable body types, heights and weights. This past New Year, we made an agreement to measure and compare our caloric intakes, checking with online food composition tables. To our surprise, we found that we each eat just about the same number of calories every day. Despite all this, our weights and body shapes have now changed, in some cases rather dramatically. It was frustrating for me, as I have one of the larger waistlines in the group. How is it that people with similar caloric intakes can end up with such different weights? Four of us have been exercising together on and off for about 10 years. -- F.S., Brooklyn, New York
DEAR F.S.: Food composition tables, now available online through the U.S. Department of Agriculture (ndb.nal.usda.gov) and commercial sites (nutritiondata.self.com), provide information about what’s in the foods we eat. Remember that the calories they list for a given portion are nothing more than calculations of “potential energy.” The efficiency with which a fixed number of calories is utilized can vary from body to body. It’s similar to the way miles per gallon varies between the different models and conditions of automobiles.
For example, one’s basal metabolism -- the calories used while the body is at rest -- rises as the amount of muscle in the body increases. This is because muscle is “active tissue.” Fat tissue, by contrast, is not very active. Using the automobile analogy, this would be similar to how a car with an eight-cylinder engine burns more gas at idle than one with a four-cylinder engine.
Other factors include age, sex, genetic makeup, level of physical activity and the efficiency with which one digests and absorbs food. All these play into the way a given number of calories will affect a particular body at a particular period of life.
We get away with much during our youth, particularly if we are physically active. But if we scale back the exercise during our transition to adulthood, we will find our measurements advancing with the years. This becomes more likely if our dietary habits fail to change with the times. Exercise not only burns up calories, but can also increase the amount of muscle in the body, and that additional muscle mass burns more calories even when you are at rest.
As is true with most aspects of life, some people have to work harder to accomplish the same goal. Where weight is concerned, though, one’s value system should not get bogged down with comparisons to others. Rather, we should be focused on doing the best we can with what we’ve got -- or at least starting the process with that as our goal.
Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to firstname.lastname@example.org. Due to the volume of mail, personal replies cannot be provided.