DEAR DR. BLONZ: What are your thoughts about using pork fat (like uncured bacon or pork belly) to prepare foods? I find the taste infinitely superior to butter for most cooking needs, and there is no evidence that it is harming my cholesterol levels. I normally store the stuff at room temperature, on the theory that that's how my grandma did it (just put it in a can and scoop it out as needed). How long is it safe to leave out? Is it likely to become carcinogenic at some point, or does it just get rancid if it's too old? -- E.D., Sacramento, California

DEAR E.D.: I would not classify lard as a "go to" cooking fat, but if you have an otherwise healthful diet and are in good health, the occasional use of lard should not pose a problem.

As to some of your specifics, it's unlikely that your lard will become carcinogenic per se, but some of the lipids may oxidize if it is kept at room temperature. Mono- and poly-unsaturated fats, and especially cholesterol, are susceptible to oxidation, and the consumption of oxidized cholesterol and oxidized fats can contribute to health problems.

Many people don't realize that lard is approximately 47 percent monounsaturated and about 12 percent polyunsaturated fat. About 41 percent of lard is saturated fat, and much of that is stearic acid: a saturated fat that has been found to have a neutral effect on blood lipid levels. Finally, there are about 12 milligrams of cholesterol per tablespoon of lard.

If you are intent on using pork fat, I would recommend keeping it refrigerated in a sealed container with a minimum of airspace. Lard manufacturers often use synthetic antioxidants such as BHA, BHT or propyl gallate to help preserve fats.

DEAR DR. BLONZ: You have mentioned that weight-bearing exercise is beneficial for the bones. My mom has recovered from a stroke and is not yet able to walk; it is unclear whether she will ever be up and about as she once was. She does exercises daily, but not of the aerobic variety -- more the "sitting and doing arm or leg exercises" variety. She sometimes has light weights strapped to her ankles or wrists while exercising. Would this be considered "weight-bearing" exercise? -- S.T., Phoenix

DEAR S.T.: Strength training that involves the use of weights, even light ones, is indeed considered a weight-bearing exercise. Given your mom's condition, it may be her best option for now. Most of the other weight-bearing exercises involve movements such as walking or jogging, where the weight of the body is alternately applied and removed from the long bones of the legs. Swimming, which is also an excellent exercise, is not weight-bearing, because it lacks this element.

Have her use caution so as not to overdo it, and, of course, make sure you apprise your mother's health professional of the details of her exercise regimen. Consider consulting with a physical therapist, a service covered by many health insurance plans, as this would provide a program tailored to your mother's specific needs.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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: Many articles on health and sugar make reference to insulin as an evil contributor to obesity. But we need insulin to live, and diabetes is when you don't make enough. My husband was diagnosed with Type 2 diabetes and now takes medication to produce more. The idea of insulin being bad is quite confusing. It seems like a simplification of a much more complex process. -- T.S., San Diego

DEAR T.S.: Glucose is the body's "instant fuel," the body is designed to always have it available in the blood and to keep it within a specific range. During digestion, complex carbohydrates get broken down into their individual unit parts -- primarily glucose -- which get absorbed and enter the bloodstream. No digestion is needed for simple sugars, such as glucose, fructose, honey or high-fructose corn syrup, so these are rapidly absorbed. Sucrose (table sugar) also enters the system rapidly, being split into its glucose and fructose parts during the process.

When the blood glucose level rises above its normal range, which usually happens after we have just eaten, the pancreas is programmed to releases insulin, a hormone that signals that the body has been fed. Insulin keeps the blood sugar level from getting too high by causing sugar to be pulled into cells where it can provide energy for work and other metabolic processes. The presence of insulin also indicates that our immediate energy needs have been met, and this causes glucose entering the cells to be converted into fat, the body's most concentrated form of energy, and sent off to the fat cells for storage.

Diabetes occurs when, for any of a number of reasons, there's insufficient insulin to do the job. It can occur when the pancreas can no longer produce insulin (Type 1 diabetes), or if the insulin being produced is no longer able to elicit the appropriate response (Type 2 diabetes). In either case, there isn't a sufficient amount, so diabetics have to take shots or pancreas-stimulating pills to help provide the needed insulin boost. In both cases the diet should to be adjusted to avoid instances that would cause rapid rises in blood sugar; sweets or soda, especially on an empty stomach, are examples of items that must be controlled.

Concerns about insulin relate to its association with obesity. Our fat cells get larger as we become overweight, and enlarged fat cells tend to be less responsive to insulin (this is called insulin resistance). If the body's normal insulin release is unable to clear surplus glucose out of the bloodstream, it creates an ongoing demand for the pancreas to release more, and this can become destructive to insulin-producing cells of this vital organ. Consider that elevated blood glucose (the source of energy) is constantly coupled with an elevated level of insulin (a signal to store energy as fat); it's a perfect recipe for weight gain and obesity. Between 80 and 90 percent of adults with Type 2 diabetes are obese. The good news is that many experience improvements when they begin to lose their excess pounds. It is not entirely correct to characterize insulin as "evil," but a diet and lifestyle that don't allow it to do its job can certainly have evil consequences.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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: Calories are listed on the Nutrition Facts panel of foods, so are they considered nutrients? What's the best way of figuring out how many calories we need? And is there an explanation for why nuts and seeds have so many calories? -- F.P., Sunrise, Arizona

DEAR F.P.: Calories are not nutrients; they are a unit of energy. The calorie is the basic unit of food energy in the U.S., but other common energy units are the joule and the British Thermal Unit (BTU).

The nutritional calorie is defined as the amount of energy (heat) necessary to raise the temperature of one kilogram of water by one degree centigrade.

Fats, proteins, carbohydrates and even alcohol are complex compounds that each have caloric values because, when absorbed and metabolized, they can release energy for use by the body. On a weight basis, fats contain the most calories: 1 gram contains approximately 9 calories; 1 gram of protein or carbohydrate contains 4 calories; 1 gram of alcohol contains 7 calories. Vitamins and minerals do not provide calories.

The amount of energy your body needs depends on your age, size, body composition and how much physical work you do. It is difficult to generalize what any one individual might require. A first step is to get an estimate of your basal metabolic rate (BMR), which is the amount of energy your body requires at rest.

Your BMR changes throughout your life, being highest during times of rapid growth. After age 30, it tends to gradually decrease through the rest of one's life. One contributor to the decline is the decrease in muscle mass in relation to body weight, muscles being metabolically active tissue. As an analogy, think of how an eight-cylinder car will burn more gas at idle than a four-cylinder car.

The slowdown contributes to the tendency to gain weight as we age, particularly for those who continue to eat the same way they did when they were young. For an average adult, BMR accounts for the burning of 1,200 to 1,800 calories per day. To this number, we then add the caloric requirements for your daily activities, which for a 150-pound adult might include 1.4 calories per minute for sitting still, 5 calories per minute while walking at 3.5 mph, or 15 calories per minute during a vigorous game of soccer. The total of your BMR plus your activities is the number of calories you would need to take in every day to maintain your body weight. Online calorie calculators provide an estimate of daily calorie needs based on your height, weight, age and activity level (check goo.gl/zTLXE3).

The human body is not designed to waste resources. Calories not needed at the moment get stored for later use. Humans, like other mobile creatures, store excess energy as fat -- the most concentrated form. Plants, by contrast, don't need to be mobile, and they produce their own energy from the sun. The energy in plants is stored as carbohydrates, which allows them to get more growth "bang" for their calorie "buck."

All this changes when the plant makes its seeds: With a seed, the need is for a light, concentrated source of energy -- one sufficient to fuel the plant's growth until it can sprout its own leaves and produce its own energy. This explains why we find fats and oils in the nuts and seeds of plants.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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.