What sort of diet helps people lose more weight?  Do overweight people lose more weight on a low-carbohydrate diet (like Atkins) or on a low-fat diet (like Weight Watchers and others)?

A carefully designed study published in the current issue of the Annals of Internal Medicine answers that question.  The study enrolled over 300 obese adults and randomized them to a low-carbohydrate diet or a low-fat diet.  Importantly, patients with diabetes, high cholesterol and high blood pressure were excluded.  The low-carbohydrate diet group was instructed to restrict carbohydrates and to have as much fats and proteins as needed to feel satisfied.  (This is essentially the Atkins diet.)  The group randomized to a low-fat diet was instructed to limit total calories to between 1200 and 1800 kcal per day, with less than 30% of total calories from fat.

Both groups attended periodic behavioral group sessions to discuss their progress and learn skills for persevering with the diet.  Both groups were also instructed to pursue an exercise program consisting largely of walking.  The groups were followed for two years.

The authors’ were trying to show that a low-carbohydrate diet would lead to greater weight loss, but actually the weight loss was the same in both groups.  Each group lost an average of 24 lb after one year and 15 lb (or an average of 7% of their body weight) after two years.  About a third of the participants in each group had dropped out by two years.

One lesson from this study is that perseverance in any diet program will yield meaningful weight loss.  It doesn’t matter which diet.  The second lesson, highlighted by the large numbers of drop-outs, is that this is hard to do.  So get started, and don’t quit.

Learn more:

Annals of Internal Medicine article:  Weight and Metabolic Outcomes After 2 Years on a Low-Carbohydrate Versus Low-Fat Diet

My post in 2009 comparing different diets:  Scientifically Proven Weight Loss Method: Eat Less

A friend of mine recently asked me “Is regular soda or diet soda better for you?”

I tried to probe for details.  “Are you talking about calories?  Obviously, if you’re watching your weight or restricting carbohydrates, you should have the diet soda.”

“No, I don’t mean the calories.”

“Oh, you mean the concern that the citric acid might leach calcium out of your body?”

“No.  I just mean overall, are they good or bad for you?”

This precipitated an important revelation that had been percolating in my head for years but that never actually crystallized until now.  People think of things we ingest as generally “good for you” or “bad for you”.  But nothing is globally good or bad.  Everything has specific effects, some positive and some negative.

Amoxicillin is great for Strep throat.  It’s not very useful for lupus or seizures.  Beta blockers are terrific to prevent heart attacks, but make for lousy asthma medicine.  Even water, which is essential for life, is life-threatening if inhaled.  The most universally positive health intervention I can think of is cardiovascular exercise, and even that has some risks, like muscle sprains.

With that in mind I found an interesting study in this week’s New England Journal of Medicine.  The study attempted to prevent a serious potential complication of pregnancy – eclampsia – which is dangerous to both the mother and the baby.  It was thought that antioxidants, like vitamins C and E, could prevent the chemical abnormalities that lead to eclampsia.  And besides, aren’t antioxidants good for you?

The study randomized about 10,000 pregnant women in their first pregnancy.  Half received a daily vitamin E and vitamin C supplement, and half received placebo.  The women and their babies were followed for any signs of eclampsia or pre-eclampsia.  The outcome was disappointing.  The women on the vitamin supplements did no better than the women on placebo.

So vitamin C and E don’t help prevent eclampsia.  Does that mean they’re “not good for you”?  No.  Vitamin C is essential in preventing or treating scurvy.  So if you have scurvy, I strongly recommend it.

Oh, and to answer my friend’s question about sodas, artificial sweeteners are safe as far as we know.  So I would prefer diet sodas to avoid the calories of non-diet sodas.  The only health benefit of sodas is that they contain water, which can be obtained from other sources.

Learn more:

New England Journal of Medicine article:  Vitamins C and E to Prevent Complications of Pregnancy-Associated Hypertension

This week, a study in the Journal of the American Medical Association received a lot of undeserved media attention.  The study wanted to examine the relationship between exercise and long-term weight changes among women who were eating a normal diet (i.e. not dieting).  It followed for over a decade 34,000 women who were 45 years old or older and correlated their self-reported physical activity and body weight.

The study found that on average, the women gained about 6 lb during the study.  Among women who initially had normal weight (body mass index less than 25) there was a significant correlation between amount of exercise and maintenance of weight.  Women with initially normal weight who did at least 60 minutes a day of moderate to intense exercise maintained their weight, while those who did less tended to gain weight during the study.

The authors therefore concluded that for middle-aged women who are not dieting, 60 minutes of moderate exercise daily is necessary to prevent weight gain.  This conclusion was repeated in much of the media coverage (links below) trumpeting that women should be exercising much more than we previously thought necessary.

But hold on a minute!  First of all, the study is observational, not randomized.  If you really wanted to know the effect of different amounts of exercise on weight you would randomly assign women to different quantities of exercise, make sure they were doing the assigned amount, and follow their weight.  That’s not what happened here.  The women exercised as much or as little as they wanted, and that amount was correlated with their weight change.  But that means that anything that affects both exercise and weight could have skewed the results.  Women with chronic illnesses that cause weight gain (hypothyroidism, heart failure) would tend to feel too tired to exercise and also gain weight.  These women would tend to make the statistics look worse for sedentary women, though their weight gain had nothing to do with being sedentary.

Also, the amounts of exercise was self-reported, not observed by someone objective, making it possible that women with stable weights are simply more likely to exaggerate their reported exercise.  (Which reminds me, I have to take it easy this weekend after running 3 marathons and swimming up the Mississippi River this week.)

Finally, the correlation between exercise and weight gain was only found in women with normal weights.  In women who started with a BMI over 25, there was no connection found between how much they said they exercised and how much weight they gained.  Does that mean that overweight people shouldn’t exercise?  No.  It means that there’s nothing to learn from correlations and that we can only learn from a randomized experiment.

So this tells us nothing about how much women should be exercising to maintain their weight.  Perhaps it tells us that some conditions cause weight gain and inability to exercise.  Perhaps it tells us that thin women exaggerate when reporting their exercise habits.  Perhaps it tells us nothing.

So how can you tell how much exercise you need to maintain your weight?  Weigh yourself.  If you’re gaining weight, you should exercise more.

Learn more:

Journal of the American Medical Association article: Physical Activity and Weight Gain Prevention

Los Angeles Times article:  Women should exercise an hour a day to maintain weight, study says

Wall Street Journal article:  New Exercise Goal: 60 Minutes a Day

What’s my advice to my overweight patients?  Eat less and exercise more.  I give this advice every day, but following this advice is much harder than giving it.  Overweight people frequently struggle with diet and exercise for years, sometimes successfully, sometimes regaining their previously lost weight.

And as we become more overweight as a nation, obesity is no longer just a problem for adults.  Over 5 million adolescents are estimated to be obese in the US, which predicts bad things for their likelihood of developing diabetes, high blood pressure and other health problems.  Being an obese teen can also be a serious social and psychological burden.  Anyone who remembers adolescence knows that teens aren’t always accepting, nurturing and ethical peers.

I’ve written in the past about the slowly amassing scientific evidence that surgery for obesity has definite health advantages over continued attempts at diet and exercise.  This week, that evidence is extended to adolescents.

A study published in this issue of The Journal of the American Medical Association enrolled 50 teenagers between 14 and 18 years of age with a body mass index (BMI) higher than 35.  (For a person who is 5 feet 8 inches tall, a BMI of 35 means a weight of 235 lb.)  The enrolled teens also had to have been attempting to lose weight through diet and exercise for more than 3 years.

The teens were randomized to two groups.  One group underwent laparoscopic gastric banding.  In this surgery, an inflatable plastic belt is wrapped around the upper part of the stomach, decreasing how much food can be ingested.  In post-operative follow up the band can be adjusted by inflating or deflating it, thereby calibrating how much it constricts the stomach.  The second group was randomized to a supervised lifestyle intervention involving an individualized diet plan and a structured exercise program.  The groups were followed for two years.

The results were dramatic.  The group that underwent gastric banding lost an average of 76 lb over two years, compared to an average 7 lb in the lifestyle modification group.  The group that underwent gastric banding also had a higher quality of life and improvement in other health-related measurements.

The authors were quick to caution that gastric banding is no “quick fix”.  Patients still have to eat differently and be willing to have periodic follow up, potentially forever.  The authors still recommend diet and exercise as the first choice for weight loss.  But now for the many teens who do not lose weight after many attempts, there is a proven alternative.

Learn more:

Wall Street Journal article:  Weight-Loss Surgery for Obese Teens Backed by Study

Journal of the American Medical Association study:  Laparoscopic Adjustable Gastric Banding in Severely Obese Adolescents

Weight loss is one of the most common recommendations that doctors make.  How do we know if a patient should lose weight?  We usually use the Body Mass Index (BMI) which is a way to compare a patient’s weight to her height.  (For all you math geeks, it’s the weight in kilograms divided by the height in meters squared.  For all you physicists, I know the units make no sense.)  A BMI of 18.5 to 25 is considered normal.  A BMI of 25 to 30 is considered overweight, and over 30 is considered obese.  (See the link below to calculate your BMI.)

An article in the health section of Tuesday’s Wall Street Journal reminds us that BMI may not be telling us the whole story.  The article cites a study published in the European Heart Journal last year which followed over 6,000 adults with a normal BMI.  They all had their body fat percentage measured and were followed for about 9 years.

Surprisingly, even in these adults with a “normal” weight, those with a high body fat content had a higher likelihood of high blood pressure, high cholesterol and cardiovascular disease.

This study is too small to be definitive, and it’s observational, not randomized.  So we don’t know whether lowering body fat reverses any of these risk factors.  I’m not suggesting we all run out to measure our body fat content.  Still the article suggests a few tantalizing possibilities.

First, dieting may not be enough in improving cardiovascular health.  It may decrease overall weight without decreasing percent body fat.  Exercise is critical to burn fat and build muscle, thereby decreasing percent body fat.

Second, thin people who are inactive may have a high body fat percentage and may be falsely reassured by their “normal” weight.  This is what the authors call “normal weight obesity”.

Finally, for those of you who are exercising and not losing weight, don’t despair.  You may be losing inches from your waist, burning fat and building muscle, muscle while your weight stays the same.  Going by the weight alone is a recipe for frustration when in reality your health is improving.

Learn more:

The Centers for Disease Control BMI calculator

Wall Street Journal article:  The Scales Can Lie: Hidden Fat (only by subscription)

European Heart Journal article:  Normal weight obesity: a risk factor for cardiometabolic dysregulation and cardiovascular mortality

One of my goals for these posts is to use individual studies to point out the broader trends they suggest.  This week I want to focus on our increasing understanding of the value of exercise after illness or injury.  A generation ago a heart attack meant weeks of bed rest in the hospital followed by strict instructions from the doctor to take it easy.  The weakened heart couldn’t take much exertion, we thought.  Now after a heart attack patients are told to start exercising as soon as they’re out of the hospital.  Similarly, patients with acute back pain were prescribed bed rest for days; now we encourage staying active and gradually increasing activity to decrease the pain.

This week the New England Journal of Medicine continues that trend for breast cancer patients.  One of the most uncomfortable consequences of breast cancer surgery is lymphedema in the arm.  Lymphedema is the accumulation of fluid that can happen after lymph nodes are removed during breast cancer surgery.  The affected arm can become swollen, painful and prone to skin infections.

The typical advice for women with lymphedema has been to avoid weight lifting or vigorous exercise with the affected arm, fearing that this would worsen the swelling or injure the susceptible limb.  This week’s study tested that assumption, randomizing women with arm lymphedema after breast cancer surgery to a group that engaged in closely supervised weight lifting and another group that did not.

Surprisingly, the women who were lifting weights had fewer exacerbations of their lymphedema, and had milder lymphedema symptoms than those who were not lifting weights.  Not surprisingly, the women who were lifting weights also developed better upper body strength.

So there are increasingly fewer medical reasons to be sedentary, and we can add breast-cancer-related lymphedema to the many conditions that are improved by exercise.

Learn more:

New England Journal of Medicine Article:  Weight Lifting in Women with Breast-Cancer–Related Lymphedema

CNN article:  Weight lifting benefits breast cancer survivors

Many people use the occasion of the New Year to reflect on the last year and make specific goals for the next.  Resolutions can be very helpful motivators if they are specific, realistic and written down.  Just as people make goals for their careers and their relationships, resolutions for your health are a smart way to work for achievable targets in the health-related struggles you face.

So I encourage you this week to write down your health resolutions for 2009.  Obviously, what progress is achievable is as varied as the people making resolutions.  An elderly lady with balance problems may resolve to attend physical therapy and use her walker consistently and have an entire year without falling.  A younger more active woman may resolve to train for and compete in a triathlon.  There is no objective marker for your goals.  You just have to balance ambition with realism.

My suggestion is to make the resolutions as specific as possible.  Detailed planning will help overcome procrastination and a specific goal will keep you accountable.  So don’t write

• I’m going to exercise more
• I’m going to eat less
• I’m going to lose weight

but instead write something like

• I’m going to walk for 45 minutes Monday through Friday before work
• I’m going to join Weight Watchers and attend meetings weekly
• I’m going to weigh 205 lb on January 1, 2010

If you have diabetes, you should be following your glycated hemoglobin (or hemoglobin A1C).  Write down a goal for it.  If you’re struggling with your cholesterol, pick a goal for your LDL.  If your blood pressure is too high, write down something like

• My blood pressure will be lower than 140/90 on every doctor visit

If you’re smoking, 2009 is the perfect year to quit (on a specific date that you should pick now).  Obviously, some of these goals may require your physician’s help in terms of adjusting your medications, but your doctor can’t do it alone.

Making yourself accountable to others can also help keep you on track.  Give a copy of your resolutions to your spouse, to your doctor to attach to your chart, to anyone who knows you too well and cares for you too much to let you cheat yourself.

I wish us all a year of peace, health, prosperity and happiness.

Two years ago I wrote about the controversy of routine screening for prostate cancer.  Screening for prostate cancer is usually done with a blood test called PSA.  But whether diagnosing prostate cancer early helps patients is still unknown, and there are many serious complications that result from prostate cancer treatment.  That’s why in many cases of prostate cancer watchful waiting is a reasonable choice.

The U.S. Preventive Services Task Force recently reviewed the existing evidence for and against prostate cancer screening and published their recommendations in this week’s Annals of Internal Medicine.  Their findings drew much media attention.

The new USPSTF recommendations still state that there is insufficient evidence to recommend for or against screening for prostate cancer in men 50 to 75.  But the recommendations recommend against screening for prostate cancer in men 75 and older.

There are ongoing studies now that will answer definitively whether diagnosing prostate cancer early helps.  Until those results are available, men over 75 should review these recommendations and discuss them with their doctor before making a decision about whether to have a PSA.  The test may lead to much more harm than benefit.

Learn more:

Washington Post article:  U.S. Panel Questions Prostate Screening

Screening for Prostate Cancer: U.S. Preventive Services Task Force Recommendation Statement

Some of my previous posts about prostate cancer:
The Controversies of Prostate Cancer Screening
Fighting Prostate Cancer by Doing Nothing

Tangential miscellany:

Last week’s post, The Exercise Transformation, elicited many responses.

Three readers suggested that being accountable to someone else is the key to making exercise a habit.  To that end, they recommended hiring a personal trainer, so that each episode of exercise is an appointment with someone else and is therefore harder to postpone or cancel.

Two readers thought that recommending 30 minutes of exercise on most days is a very intimidating goal for someone sedentary, and that success would be more likely to be achieved with a less ambitious initial goal, for example 10 minutes three times a week.  Once this easier schedule becomes a habit, the duration and frequency can slowly be increased.

My only disagreement with that reasonable suggestion is that I’ve had several patients tell me that the only way to make something a habit is to do it almost every day.  Even though the cardiovascular benefits of exercise only require 30 minutes of exercise three times a week, this may be harder to sustain psychologically than a daily habit.  Ultimately, I would recommend whatever works for each person.  If doing something every day seems like an insurmountable initial goal, start slower.

Finally, a reader wrote to extol the power of just showing up.  She said that when she doesn’t feel like exercising, she talks herself into it by just putting on the swimsuit and getting to the pool.  Once there, the actual swim doesn’t seem as daunting.

I’m grateful to everyone who emailed.

I usually write about an item in this week’s news or in the recent medical literature.  Forgive me from straying from that path this week to share some personal reflections.

For sedentary patients there is an enormous psychological barrier to exercise.  All primary care doctors face that barrier daily.  We encourage, cajole, practically shove our patients to become more physically active.  The vast majority of the time, despite the patient’s and the doctor’s best intentions, no change occurs.  The patient never starts exercising, or abandons his efforts after two or three days.  Habits are very hard to change.

This is very frustrating for both the physician and the patient.  Physicians knows that cardiovascular exercise lowers blood pressure, lowers blood glucose, improves mood and energy, lowers cholesterol (while increasing, HDL, the good cholesterol), decreases anxiety and improves sleep.  The scientifically proven benefits of cardiovascular exercise exceed those of many medicines and tests that we use routinely.  Patients know this too.  They know they should be exercising, but they can’t overcome the sedentary inertia.

Patients always have excellent reasons why they can’t exercise.  Usually they’re too tired or too stressed.  This is a trap, a spiral that inevitably leads to less and less activity which causes more fatigue and more stress.  The irony is that the most effective remedy for fatigue and stress (assuming serious medical and psychiatric problems are ruled out) is exercise.  So the only way to break out of the trap is to start exercising despite the fatigue and despite the stress.  “Just start exercising anyway”, doctors beg.

Don’t misunderstand; I’m not trying to get patients to compete in triathlons or climb mountains.  I just want them to start walking for 30 minutes on most days.  Shopping, chasing your kids and walking around in the office do not count.  You have to be walking just to walk.

Then, in a tiny number of cases, through psychological processes that are completely mysterious to me, a miracle happens.  A patient starts exercising.  The transformation is unbelievable.  His blood pressure drops a few points.  A few pounds are shed.  Her heartburn resolves.  And even more impressive than the physical effects are the mental benefits.  Patients tell me they can concentrate better.  They’re less anxious.  They feel great!  After a few months, they can’t imagine skipping their exercise.  It just feels too good.  It’s as much a part of their routine as showering and dressing.  It’s a habit.  Habits are very hard to change.

In the last year I’ve told three of my patients that they are on the borderline of developing diabetes.  They have each, in his own way, made the exercise transformation.  All three are more active, leaner and happier.  For the time being, none of them needs medications for diabetes.

How can doctors better encourage that transformation?  I wish I knew, and I’d love your suggestions.  All I can recommend is that you pick something you like, start slowly, do it for at least 30 minutes almost every day, and start today.

Osteoporosis, which means very low bone density, is a major risk factor for fractures.  Fractures can be catastrophic for older people, and effective medicines exist to treat osteoporosis and prevent fractures, so detecting osteoporosis before a fracture happens is very important in older patients.  Since osteoporosis is very common in postmenopausal women, screening them for osteoporosis is a well-established part of preventive care.

Though men are less likely then women to have osteoporosis, a fracture in an older man is just as potentially catastrophic.  Until now, no clear guidelines have been available to guide physicians about whether or when to screen men for osteoporosis.  Frequently, therefore, osteoporosis has been diagnosed in men after the first fracture.

This week, the Annals of Internal Medicine published a review of the medical literature about screening men for osteoporosis, and on the basis of this review, the American College of Physicians issued a clinical practice guideline for screening men for osteoporosis.  Their recommendations are:

• Clinicians should periodically perform individualized assessment of risk factors for osteoporosis in older men.
  Risk factors for osteoporosis are
  • age (>70 years)
  • low body weight (body mass index <20 to 25)
  • weight loss
  • physical inactivity
  • corticosteroid use
  • androgen deprivation therapy
  • previous fragility fracture
• Clinicians should obtain dual-energy x-ray absorptiometry (DEXA bone density scans) for men who are at increased risk for osteoporosis and are candidates for drug therapy.

Though much is still not clarified, like the number of risk factors that should prompt screening or the frequency with which screening should occur, this is a valuable start.  So if you’re an older skinny sedentary guy (or if you love one) ask your doctor about getting a test for osteoporosis.

Learn more:

The American College of Physicians clinical practice guideline:  Screening for Osteoporosis in Men