Dear Doctor: Some studies suggest that long-term calorie restriction can lengthen lifespan; others say it won't. Which should we believe?

Dear Reader: This is a perplexing question. We need energy to live, and the food we eat provides that energy. Obviously, gluttony can lead to dire health consequences, including Type 2 diabetes, obesity and high blood pressure, but less obvious is the case for decreasing caloric intake to below normal levels in order to improve health.

The benefit of calorie restriction was first seen in laboratory rats in the 1930s. Subsequent studies have shown that a 30 to 60 percent reduction in calories in mice and rats led to an increase in both the average and maximal lifespan of the rodents.

Of note, researchers found equal improvement in average lifespan among rodents that exercised to keep the weight down, but no improvement in maximal lifespan. In other words, if the maximal age of a rat is 2 1/2 years, the maximum age would increase to 3 years by calorie restriction, but would stay at 2 1/2 years by exercise.

Calorie restriction has shown benefits in chickens, spiders and even single-celled organisms.

The reason may lie in the reduction of the metabolic rate that occurs with calorie restriction. In reducing the metabolic rate, the body temperature decreases, as does the formation rate of damaging oxidative chemicals. These oxidative chemicals damage DNA, cell membranes and the protein within cells, and may be one of the reasons that bodies age. Also, calorie restriction leads to a decrease in blood sugar and body insulin levels.

As for whether the physical benefits of calorie restriction apply to humans, a 2016 study in non-obese males and females compared those who maintained their normal diets to those who had a 25 percent decrease in their caloric intake. The subjects were followed for 24 months. The calorie restriction group lost almost 16 pounds more than the control group. Further, people's moods improved significantly in the calorie restriction group, as did reported improvements in quality of life, sleep and sexual function.

When it comes to calorie restriction and longevity, note that in Okinawa, Japan, calorie intake is 17 percent less in adults and 36 percent less in children when compared to the rest of Japan. The rate of death from heart attacks, strokes and cancer is 31 to 41 percent less than the national average. This doesn't prove cause and effect, but it does suggest the need for additional research.

Clearly, calorie restriction seems to have benefits, but proving those benefits over the long term in our not-so-steady human lives? That's not easy. Certainly, however, in our world of plenty, we need to be mindful of the amounts that we eat.

(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'm about to turn 60, and when I spend the afternoon playing with my 7- and 9-year-old grandsons, I'm wiped out. Is there anything that I can do to feel and be more energetic? I want to be an active grandmother and not just sit on the sidelines.

Dear Reader: We'd like to begin by reassuring you -- it's the rare adult who can match the activity level of a young child, who is basically a marvel of perpetual motion. However, your question does address certain realities of older adulthood.

As we age, particularly when we reach our 60s and beyond, certain changes begin to take place in our bodies. We experience a decrease in muscle mass, which results in a loss of both strength and balance. A change to sleep patterns, including less deep sleep and more frequent awakenings during the night, can cause fatigue, a drop in mental sharpness and even lead to depression. Add in the various other changes that take place in the aging heart and brain, and the result is often a feeling of low energy.

Lifestyle plays a role as well. For many adults, older age or retirement means less daily contact with a variety of people, less decision-making, a lower level of physical activity and even less time spent outdoors.

As you suspected, there are some simple steps you can take to feel better.

-- Eating a diet based on lean proteins, healthful fats, a variety of high-fiber fruits and vegetables, and limited added sugars.

-- Drink enough water. It's easy to forget to stay adequately hydrated. (And no, diet and caffeinated beverages don't count. In fact, they can act as diuretics and result in net fluid loss.)

-- No smoking. Not only does smoking tobacco quite dramatically cut down on your lung capacity, it is a risk factor in heart disease and many cancers.

-- Get enough vitamin D, which is essential to bone health and helps with depression. Spending time in sunlight or taking a supplement are necessary for adequate vitamin D.

-- Make daily exercise a priority. Walking is an excellent way to get your blood flowing and your muscles moving. It takes no equipment, is low-stress, and can be done with a partner or in a group. Yoga is a great for both the body and the mind. Weight-bearing exercises are also important to muscle and bone strength, and to stability.

-- Avoid constipation. Diet, exercise and adequate water will put you on the path to regularity. If you find you're still having trouble, the occasional use of a fiber supplement and a stool softener can be helpful.

-- Be creative about getting enough sleep. Daytime naps can make a big difference. If napping isn't in your skill set, simply taking the time to lie down with your eyes closed for five or 10 minutes can leave you refreshed.

Taken as a whole, these changes to your daily routine can help you feel more energetic -- and help you to keep up with your grandsons.

(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 know that high blood pressure increases the risk of heart disease, stroke and more. However, is it still considered a risk factor if it's controlled with medicine?

Dear Reader: High blood pressure is a significant risk factor for heart attacks and strokes because it damages the arteries that supply the heart and the brain, causing them to narrow. Additionally, the heart has to work harder to deal with the resulting elevated blood pressure, increasing the risk of eventual heart failure. There is no disputing these facts.

As for whether someone with high blood pressure controlled by medication has a risk equivalent to somebody without high blood pressure, that's a good question -- and no studies have specifically tried to answer it. But researchers have studied patients with high blood pressure and the attempts to bring the blood pressure to different levels.

A 2015 breakthrough study in the New England Journal of Medicine took 9,361 patients with systolic blood pressure greater than 130 and randomly assigned them to either treatment to keep the blood pressure between 130 and 140 or more aggressive treatment to bring the blood pressure down to 120. The aggressively treated group got their blood pressure down to 121 on average, while the less aggressively treated group had an average systolic blood pressure of 136. The study was stopped after three years because of a 27 percent decrease in the overall death rate in the aggressively treated group.

A 2016 study in The Lancet combined data from 123 studies of hypertension treatment with a total of 613,815 patients. This analysis showed that for every 10-point decrease in blood pressure, the death rate decreased by 13 percent, the stroke rate decreased by 27 percent and the heart failure rate decreased by 28 percent. Like the former study, the benefits were greater with blood pressure below 130.

Lastly, an analysis of 16 studies published in 2016 in the Journal of Hypertension looked at the benefits of more aggressive treatment versus less aggressive treatment of blood pressure. The authors found a 16 percent decrease in death rate with blood pressure below 130 versus blood pressure greater than 130.

Although these studies don't directly answer your question, consider the incremental benefits of lowering your blood pressure. If, on medication, your systolic blood pressure is in the 130s, I would say that you're at greater risk than someone who is not taking medication and who has a blood pressure of 120. If you're on medication and your blood pressure is 120, it's hard to say how that compares to somebody who has a blood pressure of 120 and is not on medication.

The most important lesson is that if you have high blood pressure, you should treat it.

Also, a message for my readers: A recent column on whether to give aspirin for a heart attack in progress referred to two studies in which users received aspirin at various times. In referring to one study, the article stated that earlier users received aspirin an average of 1.6 hours before the onset of symptoms. Obviously, this should have said "after the onset of symptoms."

In referring to the other study, the article stated that patients received aspirin at least 24 hours after the beginning of symptoms. This should have said "up to 24 hours after the beginning of symptoms."

(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.)