Human Limits

Today’s post was stimulated by an e-mail exchange with Amby Burfoot of Runner’s World on reports over the past few months suggesting that lifelong intensive exercise training might be “bad” and actually increase the risk of heart problems.  The idea is that during exercise adrenaline and related hormones cause the heart to beat faster and harder.  Do this day after day for years and the thinking goes that areas of micro damage might occur.  In addition to leading to small areas of heart damage, there might also be a buildup of calcium in the blood vessels that supply the heart.  So what is the evidence to support these ideas?

First, after extremely prolonged and intense exercise like a marathon or ironman triathlon the pumping ability of the heart can be reduced by a few percent for a few days and there can be a rise in blood levels of substances released from the heart.  However, the pumping function of the heart returns to normal within a week and there is no evidence of long term heart damage.   The blood levels of substances released from the heart also return to normal.  The other tricky thing here is that the skeletal muscles of highly trained athletes undergo biochemical changes that make them more like heart muscle.  The wear and tear on skeletal muscles during a competitive event can then cause a rise in the blood levels of so-called cardiac markers that are in fact released from skeletal muscle and set off all kinds of false alarms about heart damage.

Second, no one is sure exactly what finding calcium in the coronary arteries means in asymptomatic people especially older athletes.   Also, case reports in a few people are hard to interpret and in more controlled studies it appears that the coronary arteries of lifelong ultramarathon runners are a bit bigger than those of non-runners and can also dilate more.   The figure below shows this data, and bigger coronary arteries that relax more are almost certainly a very good thing.

Third, there is some data in animal models that areas of micro damage caused by prolonged intense exercise make the heart more susceptible to dangerous irregular heartbeats.  However, in these studies aversive stimuli (tail shock) were used to get the animals to run so there is the added issue of “mental stress” in addition to exercise.   Also, the animals were doing a training regimen that was truly heroic in terms of both daily duration and intensity and how this translates to what even the most fanatical human might do over 10 or 20 years is unclear.   In other animal models, exercise training tends to protect the heart from irregular beats.

Fourth, when detailed research and data collection is done on who dies during exercise a couple of patterns emerge.  Young people who die suddenly typically have congenital problems with the electrical system in their hearts or defective coronary arteries.   Middle aged and older people typically have evidence of heart disease that in many cases probably started before they became fit or started to train.   There are also cases of heart problems in athletes likely related to acute inflammation of the heart perhaps associated with a viral illness.   However, marathon running as a whole appears to be very safe.

Fifth, all the news is not positive.  There is some evidence that lifelong training is associated with a condition known as lone atrial fibrillation.   However, the data are only suggestive and much bigger and better controlled studies are required on this topic.   This condition while bothersome is typically not life threatening and can be treated.

Perspective:  Over the last few months I have been making the case that one of the biggest public health and ultimately medical problems out there is inactivity.   Is there a cardiac risk associated with being super fit and training a whole lot?  To the extent there is comprehensive and well controlled data the answer appears to be no.  It does appear that in terms of health there are diminishing returns and that people who train “a whole lot” (say more than an hour almost every day) are not  better off than people who just do “a lot” (30-60 minutes most days).  However, people who do a whole lot of training are probably doing it for reasons other than health that include things like a need to compete, a need for time alone, or the need for some sort of big challenge in life.  Not exercising enough is extremely common and dangerous.  By contrast, a life time of exercising “too much” is extremely rare and the evidence to suggest it does long term harm to the heart is pretty speculative.

Last week in the Opinion section of the New York Times, the food writer Mark Bittman made the case in layman’s terms that Alzheimer’s disease might be considered “type 3” diabetes.   There are two main lines of evidence in support of this idea.  The first is that glucose and insulin in large amounts do bad things to the brain.   In type 2 diabetes blood levels of both glucose and insulin can be high.   The second is that diabetes is a risk factor for Alzheimer’s disease, and the increased rates of diabetes and Alzheimer’s in the population tend track each other.  However, the story is a bit more complex than simple “type 3” diabetes.

The current thinking is that Alzheimer’s is caused by the buildup of one or more proteins (one of the major ones is called beta-amyloid) in the brain that damage nerve cells and ultimately cause brain function to decline.  However, there are holes in the protein theories and drug therapies designed to lower the levels of amyloid have not improved brain function in clinical trials.   It is also interesting to note that in addition to diabetes, several behavioral risk factors seem to put people at increased risk for Alzheimer’s disease.

When I look at these risk factors I am struck by how similar they are to traditional risk factors for heart disease.   For both heart disease and Alzheimer’s, diabetes, hypertension, obesity, inactivity, and smoking all damage blood vessels and their negative effects tend to multiply in people with more than one risk factor.   Also, the only genetic risk factor with a big effect in Alzheimer’s some something called ApoE4 which affects cholesterol metabolism and can also damage blood vessels.  To me this suggests that there is an interaction between the buildup of “bad” proteins in the brain and poor blood flow to the brain.   There is also some evidence that exercise causes an increase in the levels of something called BDNF (brain derived neurotrophic factor), which promotes the growth of new brain cells even in middle aged and older people.

If you take the evidence outlined above a step further and ask what effect improvements in “life style” might have on Alzheimer’s the data is pretty startling.  Here is a quote from the summary of the key paper on behavioral risk factors mentioned above.

“At present, about 33.9 million people worldwide have Alzheimer’s disease (AD), and the prevalence is expected to triple over the next 40 years. The aim of this Review was to summarize the evidence regarding seven potentially modifiable risk factors for AD: diabetes, midlife hypertension, midlife obesity, smoking, depression, cognitive inactivity or low educational attainment, and physical inactivity…….Together, up to half of AD cases worldwide (17.2 million) and in the USA (2.9 million) are potentially attributable to these factors. “

Who knows if there will ever be a simple explanation for Alzheimer’s disease that will lead to effective drug therapy.  However, it is pretty clear that what is good for your heart is good for your brain.

Anyone who pays attention to sports in the U.S. is aware of the uproar surrounding the “blown calls” by replacement refs during the first three weeks of the National Football League season.  There have even been calls for the resignation of Commissioner Roger Goodell for his failure to settle the strike and look out for the integrity of the game.  As I follow the deep and widespread concerns about the NFL situation (in full disclosure, I am a shareholder of the Green Bay Packers), I am reminded of one of my favorite scientific studies on cardiac events during World Cup soccer matches in Germany.

The figure below shows the number of cardiovascular events evaluated by emergency physicians in Munich during the 2006 World Cup and compares them to non World Cup days in 2003 and 2005.  Days 1-4 in 2006 were for games Germany played in that did not lead to possible elimination.  Days 5 and 6 were elimination games later in the tournament.    Game 7 included Germany but was for third place, and game 8 was the final between Italy and France.  Those at the biggest risk for a game time event were typically middle aged or older men with history of heart disease and elimination game days were especially worrisome.

 The article concludes that:

“Viewing a stressful soccer match more than doubles the risk of an acute cardiovascular event. In view of this excess risk, particularly in men with known coronary heart disease, preventive measures are urgently needed.”

Data like this leads to all sorts of speculation about why anyone would care that much about a game, but the data clearly show that people do care about “their team”.  It also shows that passionate spectators can experience significant emotional stress by simply watching their team.  Substitute the words “NFL game” for soccer match and I wonder if there have been more cardiac events than normal associated with NFL games so far this season as a result of the hullaballoo over the replacement refs.  That having been said, the good news for fan health is that the referees and league settled last night……. before the playoffs.

A couple of posts ago I reviewed the “soda ban” in New York City and asked if it would work.  I also reviewed the data on the decline in smoking over the last 30-40 years and highlighted the factors responsible.   Another big public health success over the last 30-40 years is traffic safety.   This link is to an excellent Wiki site with the raw data on traffic fatalities starting in 1899.   Right after WWII (1945) about 10 people died per million miles driven and this has fallen to just over 1 fatality per million miles driven in 2010.    People are driving more and the population has increased over time but the effect is still pretty dramatic.

The traffic safety data was also recently reviewed in an interesting piece that tells us a lot about how regulations and behavioral changes intersect to influence public health.  So drive defensibly campaigns, safer roads, safer cars, seat belts, airbags, seat belt laws, drunken driving laws and speed limits have all made a difference.   The combined effects have also been even more impressive and things are likely to get even better with electronic collision avoidance systems and smart highways.

The need for a comprehensive approach to the twin problems obesity and inactivity was highlighted last week in an entire issue of the Journal of the American Medical Association (JAMA).   Here is a link to an editorial by leaders of the National Institutes of Health that appeared in JAMA on what is needed to figure out what works and what does not work.  The editorial starts by saying.

“The obesity epidemic is not the first major health crisis that the United States has faced. In recent decades, progress has been made against such daunting challenges as tobacco use, infant mortality, and HIV/AIDS. However, obesity may pose the most significant challenge yet because it involves changing approaches to 2 fundamental aspects of daily life: food consumption and physical activity. To have any chance of release from obesity’s ever-tightening grip, the nation will require broad-based efforts in every corner of society: homes, schools, community organizations, all levels of government, urban design, transportation, agriculture, the food industry, the media, medical practice, and, without question, biomedical research.”

That having been said I wonder if 30 years from now a story similar to the one highlighted above for traffic safety and last week for tobacco control will emerge for efforts to get the population to be more active, eat less and ultimately weigh less.  Based on the experience with smoking and traffic safety I am optimistic, but addressing the inactivity/obesity problem is not going to be a simple process.

For the last month or so I have been focused on the twin problems of inactivity and obesity.   Today I want to turn the tables on these problems and ask what we know about people who live a long time and remain independent.

It turns out a lot is known about who makes it into their later 80s, 90s or 100.   In other words who lives a long time and remains independent and engaged in life   One of the first people to study this topic was Dr. Lester Breslow who died earlier this year at age 97.   His obituary in the Lancet pointed out that he was a pioneer in public health showing that:

“45-year-olds who adopted six healthy habits—exercise, non-smoking, weight control, adequate sleep, moderation in alcohol use, and breakfasting well—lived longer than people with three or fewer healthy habits.”

Midlife fitness is also important because it reduces the burden of chronic disease as people age and limits the slow drift into disability and functional limitations seen in many older people.    So if you want to be a vigorous older person, be a vigorous middle-aged person.

One of the most interesting studies on this topic comes from the Honolulu Heart Project that has followed about 8,000 Japanese American males born in the early 1900s.  The study started in the middle 60s and has found that only a couple of factors explain who lives a long time and who remains healthy.  Recently the more than 2,000 men who are still alive were studied and it was found that:

“Compared with people who died at the age of ≤79 years, centenarians belonged 2.5 times more often to the highest third of grip strength in midlife, were never smokers, had participated in physical activity outside work, and had a long-lived mother (≥80) Associations for nonagenarians (90 year olds) and octogenarians (80 year olds) were parallel, but weaker.  Statistical modeling showed that mother’s longevity and offspring’s grip strength operated through the same or overlapping pathway to longevity. High midlife grip strength and long-lived mother may indicate resilience to aging, which, combined with healthy lifestyle, increases the probability of extreme longevity.”

Clearly we can’t pick our mothers, but we can chose not to smoke and to remain physically active.   Studies of the Seventh Day Adventists in California who have incorporated the ideas outlined above also live long lives and remain independent into old age.  The slide below show that Adventist men live about 7-8 years longer than other men in California, for women it was about 4-5 years.  About 70% of Adventists men make to age 80 but only 40% of the male population as a whole makes it to age 80.

Summary:  Dr. Breslow was right a few simple behaviors can have a big impact on both how long we live and how well we live.

Last week the New York City Board of Health restricted the sale of sodas larger than 16 ounces in restaurants.  The rationale for the ban is pretty straight forward and based on the ideas I have reviewed in recent posts on the “extra” calories people in the U.S. have been eating over the last 30-40 years.   Since many of the calories are coming from soft drinks, and because soft drink portion sizes have been rising, the idea is to limit portion size.    Here is a link to an article on the action of the board and some of the likely fall out.    That having been said, in this post I do not want to take a deep dive into the specifics of the NYC ban, but want to look at some larger issues about “regulating” behavior and its impact on health.  Here are a few questions to think about.

1)    Will the large drink ban “work” and lower obesity rates?  The short answer is that no one knows but perhaps clues are available from studies on what happens to obesity in schools that ban soda and other sugary drinks.   One of the problems is that if just soda is targeted people will just drink other sugary drinks or more soda other places.  At least some evidence from the schools support these ideas and suggest the ban itself might not do much for NYC as a whole.   However, there is also evidence to support the idea that limiting access to sugary beverages in schools works if it is part of a comprehensive and what might be called “common sense” approach.

“Children who attended schools where soda pop and non-low-fat salty snacks could be purchased were more likely to be obese than those at schools where such items were not sold. Children whose parents rarely or never ensured that their child was avoiding eating too many sweets, avoiding spending too much time watching TV, or engaging in physical activity were more likely to be obese than children whose parents did so always or most of the time.”

2)    Can healthy choices be “legislated’?   If we think about how much smoking has declined over the last 30-40 years (see the figure below) it is pretty clear that healthy choices can be legislated.

The same can be said for the improvements in traffic safety.  The experience with smoking suggests that effective  multi-pronged approaches  include:

• State and Community interventions – in other words, laws that do things that make tobacco more expensive, less accessible and limit thing like smoking in restaurants.
• Communication – the goal here is to counter advertising and promotion of tobacco and at the same time promote positive behaviors.
• Cessation – behavior change is key.
• Surveillance and Evaluation – figuring out what works and does not work and how to counter corporate strategies designed to work around regulations.
• Administration and management

Eating is clearly different than smoking.  No one needs to smoke, but we all need to eat so the parallels with smoking prevention and cessation and the obesity/physical inactivity epidemic are not absolute.   However, it seems to me that we are going to have to make it harder and perhaps more expensive for people to make unhealthy food and physical activity choices and do a bunch of other things as well to address this problem (or collection of problems) in a comprehensive way.  It is going to take more than just telling people to eat less and exercise more.

3)    What about the Nanny State?   The objections to things like regulating soda size frequently bring up concerns about the so-called Nanny State.    This is a complex topic and relates to just how much control “the government” should have over things that can be framed as individual choices.   On the one hand I am sympathetic to this argument, but on the other hand we live in a complex world and all of us pay a price via things like insurance premiums and taxes for the sub-optimal choices of others.  The Nanny State argument has been used to oppose tobacco control and traffic safety initiatives as well, so expect to see it used in the obesity and physical activity debates as well.  The question of course, is where does society draw the line?

In summary, I don’t think the NYC ban will do that much to curb obesity as a stand-alone policy.  However, I do expect this to be the beginning of a long drawn out battle about the regulation of the food industry on issues related to the obesity epidemic.   If the experiences from tobacco control and traffic safety are a guide expect this to go on for the next 30-40 years and expect it to take a long time to see results.    Society did not get fat overnight.

Over the last couple of weeks the focus has been on the combined problems of inactivity and obesity that are the dark side of technology and “progress”.    Today’s post is a short one and the question is can a high level of physical activity offset what might be described as a bad diet?

The figure below is from the Aerobics Center Longitudinal Study and shows how fitness and “unhealthy eating” interact in nearly 14,000 adults who were followed for up to 16 years.   People in the moderate and low fitness groups who also scored either moderately high or high on the unhealthy eating index have increased all-cause mortality.   For example, in the moderate fitness group, people who scored high for unhealthy eating had a 1.6 times greater all-cause mortality compared to people in the high fitness group who also ate well.

The authors noted that:

“One primary dietary pattern emerged and was labeled the Unhealthy Eating Index. This pattern was characterized by elevated consumption of processed and red meat, white potato products, non-whole grains, added fat and reduced consumption of non-citrus fruits. The hazard ratio for all-cause mortality in the fifth vs the first quintile of the Unhealthy Eating Index was 1.40 (1.02–1.91). This risk estimate was reduced by 13.5 and 55.0% after controlling for self-reported physical activity and fitness, respectively.”

They went on to conclude that:

“A dietary pattern high in processed meat, red meat, added fats, non-whole grains and white potato products and low in fresh fruit was a risk factor for all-cause mortality. However, the diet-disease relationship was largely confounded by fitness.”

Comment:  I am not advocating that anyone eat what might be called an unhealthy diet, but I think this study is important because it shows that exercise and fitness can limit the negative impact of a sub-optimal diet on mortality.   There may also be times in life (for example while traveling) when it is not possible to eat well and make healthy food choices, but perhaps it is possible to remain active and make sure you get a work out in.

In my September 3^rd post, I reviewed the data showing that on average people in the U.S. are eating a lot more now than they did 30-40 years ago.  In this post I want to give you just a little bit of data about where the calories are coming from.   I also hope I can shed some light on comments that both Sheila Ray and Joey Keillor made in response to the September 3^rd post.

The graph below gives some clues about the sources of the extra calories.   The left panel is about portion size and you can see that beverage portions have gotten bigger in terms of grams/eating occasion (g/EO).  The right panel is the energy or caloric density per gram of food per eating occasion.  For solid food portion, size is down per eating occasion, but energy density is up so it is a wash.  But clearly we are drinking more calories due to bigger beverage sizes.  Not shown in this slide is that eating occasions have also increased.

The authors of the study that generated this figure conclude that:

 “While all three components (eating occasions, energy density, and portion size) have contributed to some extent to 30 year changes in total energy consumption, changes in eating occasions and portion size have accounted for most of the change. These findings suggest a new focus for efforts to reduce energy imbalances in US adults.”

I should note that the authors of the study also estimate that total daily caloric consumption has increased by about 570 calories per day in adults over the last 30-40 years.  This value is in the same ball park as the value shown in the first chart from the USDA in the September 3^rd post and on the high side of estimates for increased calorie consumption over time.  Again, whatever the estimates it is pretty clear the population as a whole is eating more calories.

Is it all fructose?  Is it all sugar?

One idea that is out there is that all of this weight gain is due to increased consumption of high fructose corn syrup.  This is controversial and a review of key studies on the topic has concluded that:

“Fructose does not seem to cause weight gain when it is substituted for other carbohydrates in diets providing similar calories. Free fructose at high doses that provided excess calories modestly increased body weight, an effect that may be due to the extra calories rather than the fructose.”

 What about fast food?

The information above shows pretty clearly that we are eating more and that sugary drinks are part of the problem.   But it is even worse than that.  Here is a summary from a study of fast food consumption and obesity in teenagers.

More frequent use of fast-food restaurants that primarily served burgers and french fries was associated with higher risk for overweight/obesity; higher intake of total energy, sugar-sweetened beverages, and fat; and with lower intake of healthful foods and key nutrients. For example, those who reported burger-and-fries restaurant use on three or more occasions per week consumed nearly one additional sugar-sweetened beverage per day compared to those who reported burger-and-fries restaurant use on less than one occasion per week.

Summary

The data discussed above was used to give a snapshot of key things contributing to the “supply side” of obesity crises:

• Bigger portions sizes.
• More eating occasions.
• More calories are coming from sugary drinks, but high fructose corn syrup is a problem mainly due to the extra calories.
• Too much fast food consumption as well as the types of fast foods make a difference.

When you see this data you can see why there is a push in places like New York City to limit the portion sizes for sugary drinks.  My personal opinion is that while there may also be subtle differences in metabolism and all calories may not in fact be created equally, these issues are likely “small potatoes” when you consider the magnitude of the overeating problem.  So, the message is eat less per serving, eat less often, and carefully monitor how often and what kind of fast food you eat.  In future posts I will explore why this is so hard to do.