Dear Doctor: I can't seem to lose weight and am wondering if my gut bacteria could be to blame. How can I change it?

Dear Reader: In recent years, it has become increasingly clear that the bacteria that live in our gastrointestinal tract, also known as the gut microbiome, play a significant and far-reaching role in our health. Researchers now believe that these bacteria, which number in the trillions, have an effect on immunity, inflammation, allergies, asthma, diabetes, weight issues, and even depression and anxiety. In fact, the metabolic activity of these microorganisms, also known as probiotics, is so complex that the gut microbiome has been referred to as the "forgotten organ."

So how does the gut microbiome develop?

Just before birth, a baby's intestinal tract is sterile. The first major infusion of bacteria comes from your mother, both in the birth canal and through breastfeeding. Next come microorganisms from the physical world around you. Throughout your life, your gut microbiome will continue to evolve. Research shows that contact with pets, farm animals, soil, dust and the outdoors contribute to its diversity. Exposure to antibiotics, overuse of antibacterial products and excessive use of alcohol have been shown to damage the gut microbiome.

Although studies have linked the presence of certain strains of gut bacteria to a tendency to be lean, and the absence of other types of bacteria to obesity, the science is still in its infancy. At this time, there is no reliable information on how exactly to harness the power of the gut microbiome to address weight issues. However, considering how important a diverse array of bacteria is to good health, making some lifestyle and behavioral changes to bolster the gut microbiome is a good idea.

Eat more fiber: With what we know about the gut microbiome, the fact is you're not just eating for one; you're eating for trillions. According to new research, fiber not only provides nourishment for gut bacteria, it also helps with diversity. So skip the processed foods and snacks. Instead, choose fruit, vegetables and whole grains. New attention is now focused on prebiotics, which are indigestible fiber that are believed to nourish gut bacteria. Natural sources of prebiotics include asparagus, Jerusalem artichokes, leeks, bananas and jicama.

Choose healthy oils: Replace refined omega-6 rich vegetable oils with a good-quality extra-virgin olive oil. Amp up your omega-3 intake with salmon, halibut, sardines, kale, Brussels sprouts, flax seeds and walnuts.

Skip the sweets: According to the USDA, we Americans consume 94 grams of sugar per day, which is about half a cup. But your gut bacteria crave complex carbohydrates, so try reaching for an orange or a handful of walnuts when that afternoon snack attack hits.

Pick probiotic foods: Fermented foods like yogurt, kefir, miso, kimchi, sauerkraut, kombucha, brine-cured olives and tempeh provide a variety of friendly bacteria. No need to go overboard -- using them in moderation is all it takes.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I have heard that turmeric supplements work quite well in an anti-inflammatory capacity, with less risk than nonsteroidal anti-inflammatory drugs. What are your thoughts on turmeric as an anti-inflammatory supplement?

Dear Reader: The turmeric powder found in spice racks -- and the component of it found in supplements -- comes from the underground stem of a plant native to India and southeast Asia, which is cooked and then ground to create an orange-yellow powder. Long used in Ayurvedic medicine to control inflammation and pain and to treat upper respiratory infections, turmeric contains compounds with anti-inflammatory and antioxidant agents. The best-known and most-studied is curcumin.

One big problem with assessing the impact of curcumin is that, in its pure form, the compound is poorly absorbed by the body and is quickly eliminated. A 2016 study reviewed six studies that used turmeric or curcumin specifically for arthritis pain, comparing them to either a placebo, glucosamine or the NSAIDs ibuprofen or diclofenac. The dosage of curcumin in the studies varied from 100 milligrams to up to 2,000 milligrams per day.

The studies found that curcumin decreased pain significantly compared to placebo and that it was comparable to ibuprofen and diclofenac in decreasing pain and stiffness. Side effects of curcumin included sore throat, gastrointestinal bloating, swelling around the eyes and itching. These side effects were more frequent at doses higher than 1,200 milligrams. The authors noted that, while the benefits seen with curcumin were encouraging, the number of people involved was small and the studies had methodological flaws. Further, the longest study in this group lasted only four months, so long-term side effects or benefits couldn't be assessed.

That hasn't quelled enthusiasm for the compound, however, and the anti-inflammatory effects of it are touted even as a possible Alzheimer's preventive. Amyloid deposits are a telltale sign of the disease, and curcumin has been shown to exhibit anti-amyloid activity. Multiple studies in mice and rats genetically modified to have Alzheimer's have shown that the addition of curcumin to their diets reduced the deposits of amyloid within the brain and decreased the markers of brain inflammation. However, these animal studies used either intravenous or intraperitoneal curcumin, not oral, so I don't think that the pills you find in health food stores would be as potentially helpful.

As for cancer, research shows that curcumin can inhibit multiple cancers in a laboratory environment and in mice. This benefit was also seen in conjunction with traditional chemotherapeutic agents, suggesting curcumin might enhance the activity of chemotherapy and decrease some of its side effects. The studies are still in their infancy in humans, so it is difficult to make any definitive conclusions.

We truly need more studies of turmeric and, more specifically, curcumin before either can be recommended as a therapeutic agent. If you're determined to use one or the other for arthritic pain, I would recommend preparations of curcumin -- and in doses of less than 1,200 milligrams to minimize side effects. In the future, the benefits of curcumin may improve if it's combined with an inert substance that allows the compound to be absorbed more easily and excreted less quickly.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: What's the best type of exercise? I've been reading that high-intensity interval training can slow down the aging process. Is this really true? I'm not too keen on this approach, but I do walk at least a mile every day.

Dear Reader: First, congratulations on exercising regularly. Last year, 81 million Americans didn't take part in any type of regular physical activity at all. That means that 27.5 percent of the population was sedentary. That's terrible news because being active is an easy, affordable and effective way to maintain good health.

Our bodies change as we age. Cardiovascular capacity decreases, muscle mass is lost and body fat increases. Decades of studies show that regular exercise can prevent and even reverse these trends. Staying active boosts the immune system, improves muscle tone and balance, enhances cognitive function, improves the quality of sleep and has a positive effect on mood.

Now, a new study published in the journal Cell Metabolism adds a bit of a twist. While any amount of exercise beats sitting on the couch, a specific kind, known as high-intensity interval training, or HIIT, appears to change the body at a cellular level. Specifically, this type of exercise affects the mitochondria, which are structures within cells that make energy available to the body.

As we get older, the ability of mitochondria to generate energy decreases. HIIT reverses this trend by making mitochondria more efficient. Even more interesting, the older individuals in the study who took part in HIIT had a measurably larger increase in mitochondrial function than did the younger ones. The younger group had a 49 percent increase in mitochondrial capacity. The older group of participants showed a whopping 69 percent increase.

So what is high-intensity interval training? It's a brief workout performed several times per week. HIIT alternates bursts of intense exercise, during which muscles use more oxygen than the body has available, known as anaerobic exercise, with periods of slower activity in which the oxygen debt is repaid. Often it can be done at home with little or no specialized equipment. We recommend doing some reading and, of course, checking in with your primary care physician before you begin.

In basic terms, HIIT goes roughly like this:

-- Start with a three-minute warm-up, like jumping jacks or jogging in place. Don't rev up your heart rate just yet.

-- For the next 30 to 40 seconds, perform a high-intensity move such as scissor kicks, squat thrusts, lifting weights or running at a fast pace.

-- Slow down with 20 seconds of low- to medium-intensity activity.

-- Rest for 30 seconds, walking and breathing deeply, to recover.

-- Start the cycle again. Continue for 10 to 20 minutes.

Does HIIT slow the aging process? That depends on what you mean by aging. Yes, this study shows that in terms of mitochondrial efficiency, the clock can be turned back. But whether this translates into longevity remains to be seen. Still, in terms of potential health benefits, finding a way to make peace with your aversion to high-intensity interval training could be a worthwhile goal.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)