DEAR DR. BLONZ: At the start of the new year, I made a commitment to lose weight. I have been down this frustrating road many times in the past, but the recent passing of a friend has provided new motivation. I have used a low-carb diet with some success, but my weight loss eventually slows down to a crawl. While eating almost nothing (compared to my usual diet), my weight becomes stable, and this drives me up the wall. I am hoping for some guidance. -- F.S., Oakland, California

DEAR F.S.: Continued frustration with weight loss often comes from a misunderstanding of exactly what happens when the body fails to receive the calories needed to maintain its weight. Pounds can drop quickly when people go on fasts, opt for drastic low-carbohydrate diets, or use regimens that include diuretic herbs. Excess body fat can be lost, but some of the loss can be water weight: a type that is quickly regained when the program ends. There can also be risks with these plans.

When you go on a diet, you create a situation in which insufficient calories are consumed to satisfy the body's demand. Because the body operates on a balanced energy "budget," it needs to borrow needed energy from its "bank account" -- stored body fat. In tandem with this, the body goes on a bit of a work slowdown, letting you know that it is not pleased. You know why you are consuming less food, but your body's survival systems are not in the loop. During weight-loss diets, the body becomes a raving miser, cutting out all unnecessary uses of energy to weather what it assumes is an ongoing famine.

The net effect of all this is a reduction of our basal metabolic rate (BMR), the energy used while the body is at rest. The reduction brings about a lowering of body temperature. A dieter may notice a greater tendency toward chills and fatigue, and perhaps a need for additional sleep. These are all normal adaptations as you deprive your system of the energy it needs and expects. But perhaps the main impact of a reduced BMR is that the number of calories needed every day drops, slowing the rate of weight loss.

Exercise can become an ally to reverse this trend. When you achieve and maintain a moderate activity level during a weight-loss program, your BMR will not drop as dramatically. As the level of exercise increases, you not only reduce the drop in BMR, you burn more stored fat. Exercise has even been shown to reduce the nagging hunger that often plagues the dieter.

Statistics show that a minority of Americans keep active on a regular basis. Clearly, though, for those who embark on a weight-loss plan, exercise can be the missing link to staying on track.

A consult with your physician is always an important first step, especially if there are ongoing health problems or risk factors involved with increased activity or dietary changes. Also, having a guidebook can help with inevitable bumps in the road. I recommend "A Small Guide to Losing Big" by registered dietitian Cheryl Forberg. This book covers many aspects of weight loss, from the perspective of a nutritionist who has worked on "The Biggest Loser" television show.

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: I am considering buying a yogurt that emphasizes that it is made with special types of bacteria. Being old-school, I admit that the idea of bacteria in food being a good thing doesn't go down easy. Can you help explain this? And if I am unable to have this yogurt that often, should I take these bacteria as a dietary supplement? -- T.W., San Francisco, California

DEAR T.W.: Despite having a reputation for contributing to ill health, most are unaware that there is a vast colony of "friendly" bacteria living in the lower portion of our digestive system. Indeed, there are 10 times more of these bacteria in the colon than human cells in our bodies.

Referred to as our "intestinal flora," these microorganisms can be important to our general health. Scientists continue to learn about the extent of the flora's influence. While more or less stable, the flora can be affected by what you eat, the medications you take, and any of a number of stressors and lifestyle factors. Whenever the flora undergo a shift, there can be temporary discomforts such as cramps, diarrhea, bloating or gas.

The "diet" of the flora consists of the undigested food we eat. This helps explain why their makeup can be affected anytime we make big changes in our diet, such as the addition or removal of substances that are not efficiently digested, such as fiber. Digestive upsets can be minimized when dietary changes are gradual.

Physical or emotional stress can change our ability to digest the foods we eat, and this, in turn, can change what makes it down to the lower intestines where the flora live. Some researchers speculate that stress and shifting eating times might impact the flora and predispose the body to the discomfort and diarrhea often experienced by travelers and shift workers.

Nothing, however, affects the flora more than antibiotics. When taken to eliminate an illness-causing bacteria, antibiotics destroy friend and foe alike. This permits yeast organisms, normally kept in check by the friendly flora, to grow in greater numbers. That's one reason why those prone to yeast infections often experience flare-ups during and after taking a course of antibiotics.

Foods such as yogurt can contain the "probiotic" bacteria that can help strengthen the friendly flora. That means that one way to maintain healthy flora is to keep sources of friendly bacteria, like yogurt, acidophilus milk, or a flora-containing supplement in your diet.

Yogurt is made from milk that is usually cultured with two different bacteria: Streptococcus thermophilus and Lactobacillus bulgaricus. It tends to be tolerated by people who have lactose intolerance, because the yogurt bacteria produce their own lactose-digesting enzyme. Some refrigerated yogurts and many brands of frozen yogurt also contain added acidophilus and bifidus bacteria. These two types have special value because they can establish themselves as long-term residents in the intestinal flora.

Probiotic food supplements can be a convenient way to supply flora. Keep in mind that an effective supplement requires more than the mere presence of a "healthful" strain of beneficial bacteria; there has to be enough of it to make it through the human digestive system in sufficient numbers to have an impact. I encourage you to read more on the topic. A good start is this article on probiotics from the National Institutes of Health: tinyurl.com/hv5clnx.

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: I am a driver for a corporate CEO. He is 55 and an insulin-using diabetic. Driving him around all day I know that he often misses meals. I find him raiding the snack area in the car and want to make sure there are healthy items for him to choose from. Would fresh fruit help, and what pre-packaged snacks would be best to have? -- R.D., Santa Clara, California

DEAR R.D.: Healthful snack foods for a diabetic don't differ that much from those recommended for others. You should aim for nutrient-dense, great-tasting foods that can serve either as a bite between meals or a meal substitute. The key for a diabetic, especially one who takes insulin, is that there needs to be some idea of what is in the food so that the insulin dose can be adjusted accordingly.

Good suggestions for snacks would include fresh fruits, as you suggest, together with an assortment of nuts, seeds, pretzels and dried fruits. Keep a log of what you add and when so that you can track preferences and maintain freshness. Pre-packaged snacks containing these foods would add a measure of convenience, but I would advise you to stay away from overly sugared snack products; check the ingredient list. Asking for fruit and nut preferences could help you locate good-fit products, or you could even assemble a trail mix custom-made for your CEO (label it with his name/company and you will likely have a hit on your hands). Always have water available.

If there is a refrigerator in the car, consider stocking your CEO's favorite water, some different yogurts or fruit/vegetable juices. I would also stock a selection of meal replacement bars. Find ones that provide balanced nutrients to help fill in for any missed meals. If you tend to drive regular routes, have a list of locations that have healthful foods ready-to-go.

In all cases you should have a sheet that contains a nutrient breakdown of the various foods. You can get these from the labels, from books or online sites, such as nutritiondata.self.com. I think your CEO is fortunate to have you in the driver's seat.

DEAR DR. BLONZ: Is there any truth to the concern that antiperspirants cause breast cancer, indeed that they are the leading cause? Could you shed some light on this, and if so, could you also recommend a suitable alternative? -- B.B., San Jose, California

DEAR B.B.: This is not a food or nutrition-related issue, but I think it is important to squash these types of rumors. There is no evidence that antiperspirants cause breast cancer. About the closest thing to it is the fact that it is not recommended that women use certain antiperspirants or skin lotions, creams or ointments prior to having a mammogram. The thought here is that the metal salts in these products might interfere with a proper reading. There are evidence-based sites to check out suspicious stories, one being snopes.com.

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.