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 questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: My grandmother used to encourage us to eat the inner white part of the orange skin, saying that it is a secret part of the food that has special qualities. Dutifully, I have followed this advice for a lifetime. Finally, realizing that the science behind nutrition was not as well known in her day, I have come to question the advice’s worth. What, if anything, is the value of this part of the orange? -- S.N., Lombard, Illinois

DEAR S.N.: Your grandmother’s advice may not have been drawn from research findings of the day, but it does reflect an intuitive appreciation for citrus fruits, and whole foods in general.

The entire orange contains a number of naturally occurring compounds that have been associated with disease prevention in humans. But please note that simply because a substance can be found in a food, that doesn’t mean there is enough of it to have a significant beneficial effect in our bodies. These are compounds that evolved to protect the fruit’s seeds, as well as the flesh that the seeds rely upon for sustenance until they get their first sprouts into the sun and begin producing their own energy.

Aside from the vitamin C that we associate with citrus, there are a number of substances in the peel and in the white inner portion, or albedo, of the citrus peel. The list includes bioflavonoids, limonene, glucarate, pectin and soluble fiber. If you consume the outer part of the peel, expect it to contain residues from any sprays used by the grower -- so select your citrus provider carefully and scrub the fruit before eating. Citrus zest is quite flavorful and is often used for culinary purposes, but only use zest from well-washed, organically grown fruit.

Other fruits and vegetables offer similar types of protective substances, but science is still in the discovery stage about their range of potential health benefits for us -- along with how they might work together, and what effective doses would be. I salute your grandmother’s whole-food wisdom.

DEAR DR. BLONZ: There are many half-and-half products in my dairy case. Some are pasteurized, and others are ultra-pasteurized. What is the difference? -- D.C., San Jose, California

DEAR D.C.: Pasteurization and ultra-pasteurization are heat treatments designed to reduce the presence of potentially harmful microorganisms. The two differ in the amount and duration of heat used.

Pasteurization heats a dairy product to 160 degrees F for 15 seconds, while ultra-pasteurization heats the product up to 280 degrees F for up to 3 seconds. The higher heat used in ultra-pasteurization eliminates more bacteria and results in a more shelf-stable product. Once opened, however, both types of products require refrigeration.

Ultra-pasteurization is not widely used because the high heat can affect flavor, so the process is usually reserved for products such as half-and-half or whipping cream. However, ultra-pasteurized milk can be found in remote areas, or in stores that don’t sell a high volume of dairy products.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: I have eaten well, staying away from high-fat foods, but have always held that after a person reaches 80, fat intake isn’t as harmful as it is in younger years. There are foods I would like to eat more of, but the high fat content has always stopped me because of the harmful effects it can have on the body. I am now 87. Please advise if there is a difference when the 80-plus age is reached. I do not have a weight problem. I wish to thank you for any information you can give me. -- N.F., Phoenix

DEAR N.F.: You seem to have found a good road in life, and your 87 years speak volumes. Why not enjoy the foods you’d like to eat? What are you waiting for?

A general belief that dietary fat is “harmful,” for individuals at any age, is misleading and somewhat dated. What counts is the amount and types of fat in relation to the other healthful attributes of the diet. (About the only exception are trans fats, and those are finally on the run with the latest labeling changes that require their divulgence.)

Examples of foods naturally high in fat include nuts, seeds and fruits such as the avocado and olive. These plants need their fats to reproduce, and they have succeeded over the millennia because they also produce protective phytochemical compounds to keep the fats viable. In the same way, we need to be sure that our body receives essential nutrients and healthful components from whole foods as its protectors. You then fold into this recipe an active lifestyle to keep the machinery in good operating condition. It is a simple, straightforward theme, and fat ceases to be an issue when this balance is in place.

You say that your weight is not an issue, but you didn’t indicate whether there are any other health issues you might be dealing with, or if there are medications that may be a part of your daily regimen. The food issue is straightforward, but if there is a delicate balance of ongoing medical concerns, it makes sense to touch base with your health professional before you make any radical changes.

DEAR DR. BLONZ: What does it mean when an oil is “winterized”? A bottle had this listed on its ingredient statement. The store manager had no idea, so I thought I would ask you. -- O.Q., Seattle

DEAR O.Q.: Winterization is the process by which saturated fatty acids are filtered out of an oil to help it stay clear at cooler temperatures. Oils begin to turn cloudy as the temperature drops. Similar to the way that water forms ice crystals as it freezes, the fatty acids of an oil form into crystals on their way to becoming a solid block of fat. Saturated fats have the highest melting point, which means that they are the first to solidify as the temperature drops. Polyunsaturated fats, by contrast, have low melting points, so they remain clear and liquid at cooler temperatures. The winterization process chills the oil slowly and filters out some of the crystalized saturated fatty acids. This allows the oil to remain clear at cooler temperatures.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.