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Get your copy of Exercise: A program you can live with What can improve your mood, boost your ability to fend off infection, and lower your risk for heart disease, diabetes, high blood pressure, and colon cancer? The answer is regular exercise. This report answers many important questions about physical activity, from how your body changes through exercise to what diseases it helps prevent. It will also help guide you through starting and maintaining an exercise program that suits your abilities and lifestyle. Click here to read more »

Exercise limits weight gain in normal-weight but not heavier women

As most of us know, about two-thirds of adults in the United States are overweight or obese, and excess weight is a major health problem. Weight gain occurs when energy intake (calories consumed) exceeds energy output (calories burned).

Many studies have shown that physical activity can promote weight loss among people who are overweight or obese, but far fewer have investigated whether it can prevent unhealthy weight gain in the first place. That’s the focus of a study by Harvard Medical School researchers published in the March 24/31, 2010, issue of The Journal of the American Medical Association. The research team was led by Prof. I-Min Lee of Harvard Medical School and Harvard School of Public Health, who is on the advisory board of Harvard Women’s Health Watch.

The researchers analyzed data provided by 34,079 healthy women, average age 54, who were participating in the long-term Women’s Health Study. Between 1992 and 2007, the women reported their body weight and physical activities every three years. They also provided information on matters that could affect the link between physical activity and weight change, such as smoking, postmenopausal hormone use, alcohol intake, and diet.

Participants were divided into three groups based on their level of physical activity, with energy expended in each group expressed in metabolic equivalent (MET) hours per week. A MET is a unit used to estimate the energy expended during physical activity, relative to the energy expended while sitting quietly.

The results

Not surprisingly, moderate-intensity activity, such as brisk walking, consumes more METs than lower-intensity activities such as yoga or stretching. In the study, women at the lowest activity level got less than 7.5 MET hours per week, the minimum recommended in federal guidelines (it’s the amount expended in walking briskly for 30 minutes, five days a week). The middle group got 7.5 to less than 21 MET hours per week; and the most active women got 21 MET hours or more per week, which requires at least 60 minutes per day of moderately intense physical activity — or 30 minutes per day of vigorous activity.

Over the course of the study, the women gained 5.7 pounds, on average. Those who exercised less tended to gain more: over any three-year period, women in the low and middle activity levels were more likely to gain 5 or more pounds than the most active women. When the researchers looked only at the 4,540 women who were normal weight (a body mass index of less than 25) at the study’s outset and who had managed to hold their weight in the normal range, they found that these weight-maintainers averaged 60 minutes of moderately intense activity per day.

What it means for women looking to control weight

Among normal-weight women, the likelihood of putting on weight decreased as physical activity level increased. Among women who were overweight or obese, there was no relationship between physical activity and weight gain.

Thus, for women who aren’t overweight or obese, exercise can keep off excess pounds, but it must add up to about seven hours per week of moderately intense activity such as brisk walking or casual bicycling — or 3.5 hours per week of vigorous activity such as jogging or aerobic dancing.

For women who are already overweight or obese, increased physical activity alone is not enough to prevent further weight gain. These women also need to reduce their calorie intake. But they should still get at least 30 minutes of moderately intense physical activity most days for the sake of the many health benefits, which include a reduced risk of chronic conditions such as heart disease and stroke.

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Get your copy of The Aging Eye: Preventing and treating eye disease As we age, problems with eyesight become more common. Despite this, many people are not conscientious about caring for their eyes. Learn how to recognize the risk factors and symptoms of specific eye diseases — cataract, glaucoma, age-related macular degeneration, and diabetic retinopathy — and what steps you can take to prevent or treat them before your vision deteriorates further. Click here to read more »

What can I do to prevent cataracts?

Q. Is it true that cataracts are made of calcium? Can I do anything to avoid getting a cataract? What about diet?

A. A cataract is a vision-clouding area in the lens of the eye. About half of all people ages 65 to 74, and 70% of those ages 75 and over, develop cataracts, which are the leading cause of blindness worldwide. Fortunately, surgery is safe and effective; in places like the United States, where it’s one of the most common operations performed, it leads to improved vision in about 90% of cases.

Cataracts aren’t made of calcium but rather of clumps of protein. Normally, the lens of the eye works like a camera lens to focus light on the retina at the back of the eye (see illustration) and to adjust the eye’s focus, which allows us to see things clearly at varying distances. The cells of the lens are composed of water and protein arranged in a way that keeps the lens clear. For reasons that aren’t fully understood, the protein molecules may clump together and start to cloud the lens. This is the beginning of a cataract. The effect has been likened to cooking an egg white.

You may not notice anything at first, but cataracts typically progress, becoming denser or clouding more of the lens and blurring vision. Eventually, vision may be so severely affected that surgery is needed to remove the lens and replace it with an artificial one. Cataracts usually form in both eyes but may not progress at the same rate or affect vision equally.

We know how to treat cataracts, but we don’t know much about why they develop. Aging is obviously a factor — possibly because of changes in the chemical composition of the lens or possibly because of normal wear and tear. Most people develop some lens opacity, or clouding, by the age of 60. Other risk factors include injury to the eye, previous eye surgery, diabetes, use of corticosteroid drugs, and having a family member with cataracts. Many studies have implicated smoking and drinking as well. And a study suggests that hormone therapy may increase the risk. Cataracts also seem to be more common in people who’ve had long-term exposure to sunlight.

We don’t know if avoiding or treating these risk factors will prevent a cataract from forming. But it can only do you good to refrain from smoking, moderate your alcohol consumption, and protect your eyes from sunlight with hats and sunglasses.

Evidence regarding the role of diet in cataract prevention is mixed. Some experts believe that antioxidant vitamins might help prevent cataracts by getting rid of molecules called free radicals, which may trigger or fuel protein clumping. But despite several studies, there’s no convincing evidence yet that vitamin supplements prevent or slow cataract growth. In a 2008 Archives of Ophthalmology study, researchers found that women ages 50 to 79 whose diets were rich in lutein and zeaxanthin had fewer cataracts. These phytochemicals are abundant in dark green leafy vegetables such as spinach, kale, Swiss chard, watercress, and dandelion greens. But these vegetables contain many other healthy substances, so it’s not clear whether lutein and zeaxanthin are responsible for the eye benefits.

In any case, you should have your eyes examined every two years (annually after age 60). And even if you can’t do much to prevent or slow the growth of cataracts, you can reduce their impact on your life in various ways, such as adjusting your eyeglasses, getting anti-glare sunglasses or magnifying lenses, or just using brighter lights at home and work.

— Celeste Robb-Nicholson, M.D.
Editor in Chief, Harvard Women’s Health Watch