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

This week I discovered how painful it can be to change a habit.  Not because it means admitting I was doing the wrong thing, but because it means analyzing how feeble my reasons were for the habit in the first place.

Ever since I started practice I’ve been recommending calcium supplements to post-menopausal women.  Why?  Mostly out of habit.  There’s not a shred of evidence that calcium supplements prevent fractures, but some suggestion that they may help bone density.  But what’s the harm?  Calcium supplements are safe and wholesome and natural, right?

Last week the journal BMJ published a meta-analysis of randomized trials which compared calcium supplement against placebo.  (Expand your geeky medical literature vocabulary!  A meta-analysis is a study that systematically reviews already published studies on a particular topic and statistically pools together the results of all these studies.  The goal of a meta-analysis is to reach a more definitive conclusion than the individual studies did.)  It’s important to note that these trials were not studying the effects of calcium supplement on heart attacks.  They were each looking at the effect of calcium on different outcomes – bone density, fractures, colon cancer, whatever.  The investigators looked through the original study data and (where the data was available) counted the numbers of heart attacks in patients taking calcium supplements and in those taking placebo.

For the studies in which data was available on individual patients, about 3.5% had heart attacks on calcium while about 2.7% had a heart attack on placebo over an average follow up of 3.6 years.  That may not seem like a big difference but it means that for every 69 patients on calcium rather than placebo for 5 years there was one extra heart attack.  Some media reports characterized this as a small increased risk of heart attacks, but it’s not.  It’s in the same numerical ballpark as the decrease in heart attacks from treating high blood pressure.

Even if this harm was numerically small, remember, we have to weigh it against a completely unproven benefit.  Doctors have been recommending calcium supplements on the assumption that they prevent fractures, an assumption that has not been demonstrated in trials.  The study calculates that, even taking optimistic estimates for fracture reduction from calcium supplements, treating 1,000 people with calcium supplements for five years would cause an additional 14 heart attacks and prevent 26 fractures.  That’s a terrible tradeoff.

So calcium supplements seem to be a bad idea.  But there are some important additional points.  First, the authors were careful to state that dietary calcium (calcium in your food, not in supplements) has never been implicated in heart attack risk and is presumably safe.  So we should be getting our calcium in our diets, not in supplements.  Second, this study did not address vitamin D, which has many proven benefits that calcium does not.  So keep taking your vitamin D supplements.  Finally, patients with osteoporosis who are taking medications that rebuild bone need excellent calcium intake for the medication to be effective.  In these patients, who are at high risk for fracture, the benefit of calcium supplements may be greater than the risk.

An editorial in the same issue of BMJ concluded that “given the uncertain benefits of calcium supplements, any level of risk is unwarranted,” and that calcium supplements “should not be given without concomitant treatment for osteoporosis.”

So as painful as it is to change my mind about something I thought was completely benign two weeks ago, for my patients who do not have osteoporosis, I recommend stopping calcium supplements.  Obviously, if you have questions about your unique situation, ask your doctor.

Maybe next week I’ll find out that smelling roses causes seizures.

Learn more:

BMJ article:  Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis

BMJ editorial:  Calcium supplements in people with osteoporosis

LA Times Booster Shots:  Calcium supplements increase the risk of heart disease in the elderly, study says

Everyone knows that caffeine is useful on occasion if we need to stay alert, especially when we’re sleepy.  Is there any college graduate who hasn’t had a caffeine-fueled all-night study session before an exam?  I certainly remember several nights in which I drank coffee to the point of inability to blink, much less sleep.

But for those who drink a lot of coffee daily, how much of a boost in alertness are they getting?  A study in this issue of Neuropsychopharmacology offers an interesting insight.

Over 300 subjects were randomized to receive either caffeine tablets or placebo tablets.  They all had to abstain from caffeine for 16 hours before the experiment.  The caffeine group then received a 100 mg caffeine tablet and 90 minutes later a 150 mg caffeine tablet.  (These doses are roughly the amount in a cup of coffee.  See the Mayo Clinic link below for an interesting review of the amounts of caffeine in different beverages.)  The placebo group received a placebo tablet and 90 minutes later a second placebo tablet.  The subjects were asked about headache and alertness before and after each dose.

The responses varied depending on the subjects’ usual caffeine use.  Those who normally were moderate to heavy users of caffeine reported an increase in headache and a decrease in alertness after placebo but not after caffeine.  So after caffeine they were feeling normal and without it they were having withdrawal symptoms – headache and sleepiness.  Surprisingly, even those who normally use little or no caffeine didn’t report any more alertness after caffeine than after placebo.  But at least they weren’t having withdrawal symptoms with placebo.

So it sounds like heavy coffee drinkers aren’t getting a boost from their coffee.  They’re just avoiding withdrawal.  They should probably slowly decrease their use of caffeine to more reasonable ammounts.

And those of us who drink little coffee are probably experiencing a boost from psychological conditioning as much as from caffeine.  We expect the hot fluid that we know so well to make us more alert, so it does.  If someone slipped us decaf without our knowledge it would likely work almost as well.

To celebrate this new-found wisdom, I’m going to go home and drink Diet Coke until I have palpitations.

Learn more:

BBC News article:  ‘People become immune to coffee boost’, experts believe

Mayo Clinic article:  Caffeine content for coffee, tea, soda and more

Neuropsychopharmacology article abstract:  Association of the Anxiogenic and Alerting Effects of Caffeine with ADORA2A and ADORA1 Polymorphisms and Habitual Level of Caffeine Consumption

Tangential miscellany:

I’m happy to report that US Airways Magazine has reprinted my post Erroneous Evidence About Enough Exercise in their current issue.  So if you’re flying US Airways this month please grab a copy and brag to your friends that you were reading my posts years before I was cool.

Two weeks ago I wrote a post about the mistake we make when we think of some medicine or food as generally “good for you” or “bad for you” as opposed to having specific benefits and harms.  I started with an anecdote in which a friend asked me whether diet sodas or regular sodas were better for you.

Susan Dopart, a terrific dietitian who I’ve known for over a decade, emailed me to bend my thinking about diet sodas and about non-nutritive sweeteners (i.e. artificial sweeteners) in general.  With her permission, I thought I’d share her thoughts with you.

She shared with me an article reviewing studies that link the use of artificial sweeteners with various adverse health outcomes, like obesity and insulin resistance.  The studies were all observational, that is, not randomized.  For example, one study showed that people who drink more diet sodas tend to weigh more than people who drink fewer diet sodas.  That’s exactly the kind of study that makes me want to pour lemon juice on my paper cuts.  The media misunderstands this kind of study and reports that diet sodas cause obesity.  But an equally likely possibility is that people who have stronger cravings for sweets will be overweight (by eating actual sweets) and will also drink more diet sodas (because they’re sweet).  It’s like noticing that my lawn wilts on the same days that the beaches are crowded and blaming the crowds for my wilting lawn.  But both are caused by a third phenomenon – hot days.

So, fancying myself the Defender of Science Against Confusing Nonsense, I emailed Susan that the studies were completely unconvincing and that artificial sweeteners haven’t been proven to have any adverse health effects.  Susan agreed that there is no solid science on the subject, but said that in the absence of good science the best guide we have is our professional experience.  She certainly has lots of experience, and she believes that sweeteners, whether natural or artificial, increase cravings for more sweets.  In her experience patients who have stopped drinking any kind of soda have noticed their cravings for sweets decrease.

That’s a potentially important lesson, and someone should test it rigorously.  In the meantime, I appreciate Susan sharing her expertise with us.

Learn more:

There is a mechanism that could explain how sweets cause increased cravings for sweets.  It’s a theory by psychologist Seth Roberts that weight gain is mediated by a learned association between tasty foods and calorie content.  This hasn’t been tested in a good study (yet) but I found his paper intriguing and easy to read.  (I have no idea what Susan Dopart thinks about it.)

What Makes Food Fattening?  A Pavlovian Theory of Weight Control by Seth Roberts

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

Mercury in high doses is known to be toxic.  So if you were thinking about breaking your glass thermometer and drinking the contents on a lark, I beg you to reconsider.  This has raised concern about possible harm from eating seafood since many species of seafood are known to contain trace amounts of mercury.  Much hand-wringing has ensued.  Should we shun salmon?  Avoid albacore?

The most recent issue of The Medical Letter, a publication I frequently cite, summarizes the scientific literature and attempts to clarify the issue.

Mercury exposure during pregnancy has been associated with problems with neurological development in the developing babies, though the results of studies of the effects of seafood intake during pregnancy have been mixed.  Still, because neurodevelopment appears to be the biggest effect of mercury toxicity, concern has focused on pregnant and breastfeeding women and small children.  The FDA (see link below) has recommended that pregnant and breastfeeding women limit their intake of seafood high in mercury.

In non-pregnant adults, no harm has been shown from mercury exposure from seafood.  One possible reason is that the omega-3 polyunsaturated fatty acids (PUFAs) in fish oil have a beneficial protective effect that could outweigh any harm from the mercury in fish.

The authors of the article conclude:

Public health agencies have recommended limiting the intake of seafood with a substantial mercury content during pregnancy. Since the typical US seafood diet has a healthy ratio of omega-3 PUFAs to methylmercury and PCBs, the net effect of eating fish in the US is likely to be a protective one.

This is reassuring.  I’m going to celebrate with a jar of herring.

Learn more:

The Medical Letter article:  Mercury in Fish (by subscription only)

FDA advisory for Women Who Might Become Pregnant, Women Who are Pregnant, Nursing Mothers and Young Children:  What You Need to Know About Mercury in Fish and Shellfish

Folic acid, a vitamin found naturally in green leafy vegetables and legumes, is essential for making the building blocks of DNA.  And since copying DNA is an important part of what cells do before they divide, it’s critical for cell division.  Developing fetuses have very rapidly dividing cells, so it’s not surprising that folic acid deficiency has been linked to birth defects, specifically brain and spinal cord abnormalities.

To prevent these birth defects, physicians for many years have recommended folic acid supplements to pregnant women and women planning pregnancy.  The problem is that folic acid deficiency harms babies in the first weeks of pregnancy, before many women know they’re pregnant and before they seek prenatal care.  In an effort to end folic acid deficiency more comprehensively, the U.S. began requiring that flour and other grains be fortified with folic acid in 1998.  The incidence of brain and spinal cord birth defects subsequently declined.

So if folic acid is good for pregnant women, might it have benefits for everyone else?

Well, unfortunately, no other major benefits have been found to taking folic acid supplements.  Folic acid deficiency can cause anemia, but that’s rare and is easily treated (with folic acid!) when diagnosed.  Back in the 1940s it was noted that leukemia patients tended to have low folic acid levels.  It was hypothesized that folic acid deficiency played a role in leukemia and a trial was done in which leukemia patients were given folic acid.  Surprisingly, they died sooner than the patients getting placebo.  Their folic acid levels were low because it was being used up in the rapidly dividing leukemia cells; giving them more folic acid helped the leukemia cells divide faster.

Since then folic acid supplementation has been linked with other cancers.  Though the findings were not definitive, given the absence of proven benefits (in those of us who are not women in child-bearing age) there is no compelling reason to recommend folic acid for everyone.

This Monday’s LA Times had two very helpful articles which summarized the controversy.

The U.S. Preventive Services Task Force (USPSTF) reviewed the evidence on folic acid and reissued their recommendations this month.  The USPSTF recommends that all women planning or capable of pregnancy take a daily supplement containing 0.4 to 0.8 mg (400 to 800 micrograms) of folic acid.  There is no recommendation for men or for women not in their child-bearing years.

The rest of us should probably just eat our veggies.  If you do take a folic acid supplement (and I don’t) make sure it doesn’t contain more than 1 mg (1,000 micrograms) of folic acid.

Thanks to Ron T. for pointing me to the LA Times articles.

Tangential miscellany:

On Memorial Day my partner, Dr. Dorothy Lowe, and some of our staff and I will be riding in the Acura LA Bike Tour.  Register to ride with us, or come out to cheer and watch the spectacle of thousands of riders taking to the streets.  You don’t have other plans for 5 a.m., do you?

Learn more:

LA Times articles:  Folic acid might be losing its sheen and Folic acid is important, but take care not to overdo it

Folic Acid for the Prevention of Neural Tube Defects: U.S. Preventive Services Task Force Recommendation Statement

Few things captivate the public more than a new diet.  From Atkins to Ornish to the Mediterranean diet, each new theory attracts attention and true-believer adherents and generates lots of book sales and interviews on daytime TV.  People passionately argue about whether a diet low in carbohydrates or low in fat is best for weight loss.  But until now no large trial has ever been done to answer the question.

This week’s New England Journal of Medicine published the largest study that directly compares different diets to measure which yields the greatest weight loss.  Over 800 overweight adults were randomized to one of four different diets.  (Importantly, diabetics were excluded.)  They were all given diets calculated to provide 750 calories fewer than they were burning daily, but the four diets differed in the percentage of calories from fat, protein, and carbohydrates.  Two of the diets were low-fat and two were high-fat.  Two were average-protein and two high-protein.  And the four diets provided a broad range of carbohydrate intake from low to high.

The participants were also asked to participate in periodic group counseling sessions and were instructed to do 90 minutes of moderate exercise per week.  They were followed for 2 years and their compliance with group attendance, diet and exercise was tracked.

Interestingly, the four diet groups lost weight at the same rate.  Six months into the study the participants lost an average of 13 lb, 7% of their body weight.  After that, on average, they slowly regained weight, so that by two years the average weight loss was 9 lb, the same in all four groups.

So diet and exercise lead to weight loss, and whichever low-calorie diet you can stick to is as good as any other.  So get started.  You can still buy the latest diet book and swear that it’s the best because your favorite actor lost weight on it.  Only you and I will know that you owe your success to the New England Journal of Medicine.

Learn more:

New England Journal of Medicine article:  Comparison of Weight-Loss Diets with Different Compositions of Fat, Protein, and Carbohydrates

NY Times article:  Study Zeroes In on Calories, Not Diet, for Loss

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.