June 1st, 2012

Reality Check: Stop Exercising and Eat Chocolate?

It’s been a terrific few days of medical news for lazy people and chocoholics.

First, a study in PLoS One provided ammunition to the exercise-averse crowd by claiming that exercise can actually be bad for some healthy people. As an added bonus, a story about the study was carried on the front page of the New York Times.

Less than a day later, in a moment that will be long treasured by chocoholics, a study in BMJ calculated that people with metabolic syndrome could reduce their risk for serious cardiovascular events like heart attacks and strokes by eating dark chocolate every day.

Let’s take a quick look at each study:

The exercise study used data from 1687 people who participated in one of six different exercise studies and found that a surprisingly large percentage of people had a significant adverse change in one of several important risk factors:

  • Increase >24 pmol/L in fasting insulin: 8.3%
  • Decrease <0.12 mmol/L in HDL cholesterol: 13.3%
  • Increase >0.42 mmol/L in triglycerides: 10.3%
  • Increase >10 mm Hg in systolic blood pressure: 12.2%

The researchers were unable to find any factors that helped predict which patients would have an adverse change. Approximately 7% of the people in the study had adverse changes in two or more risk factors. The researchers didn’t discuss whether the types of changes they observed might also have been found in people not in an exercise program.

The NIH’s Michael Lauer  praised the study and told Times reporter Gina Kolata: “We do not know whether implementing exercise programs for unfit people assures better outcomes. That has not been established.”

Steve Nissen provided a sensible perspective on the study for MSNBC:

With any therapeutic intervention, there are always responders and non-responders. No intervention produces benefits in 100 percent of subjects. Biological systems are complex and many other factors can alter the response to any intervention.

Moving from the savory to the sweet course, the BMJ study reported that daily consumption of dark chocolate can prevent cardiovascular events in people with metabolic syndrome. Dark chocolate has been shown to lower blood pressure, and may have additional beneficial effects on lipids and other metabolic factors.

Australian researchers used a sophisticated mathematical model to estimate the effect of eating chocolate in people with metabolic syndrome who had a systolic blood pressure 121 mm Hg or higher and were not taking antihypertensive medication. They calculated that daily dark chocolate could prevent 8.5 CV events over 10 years in 1000 people with metabolic syndrome.

The researchers concluded that the findings of their study “suggest that the blood pressure lowering and lipid effects of plain dark chocolate could represent an effective and cost effective strategy for the prevention of cardiovascular disease in people with metabolic syndrome (and no diabetes).”

I’d like to call attention to one additional detail of the study. The authors note that they modeled a “best case scenario” that assumed 100% compliance. Normally I would be skeptical about this sort of assumption, but since we’re talking about chocolate I think we’re much more likely to see a problem of over-compliance rather than under-compliance. The authors acknowledge that their study did not include any of the other possible effects of dark chocolate, including its “additional caloric and glycemic load.” But in a study population of metabolic syndrome, and in a world in which obesity and diabetes are growing exponentially, this seems a strange omission.

It’s hard to imagine how these two studies might contribute to efforts to combat cardiovascular disease. Would anyone seriously suggest that exercise should not be recommended to the vast majority of people? Does anyone really believe that chocolate has an important role to play in curbing the impact of metabolic syndrome? These studies may provide a small addition to the academic literature on cardiovascular disease, but it’s difficult to see how they contribute to public health.

9 Responses to “Reality Check: Stop Exercising and Eat Chocolate?”

  1. The premise of PLoSOne is for the peer review process to occur after publication. Approximately 70% of submitted manuscripts are accepted so that “judgments about the importance of any particular paper are then made after publication by the readership (who are the most qualified to determine what is of interest to them).”

    This is an important and heretofore unmet need, which expedites the publication process and sharing of ideas. Keeping this in mind, it is important to highlight the significant limitations of the study, which are not addressed in The New York Times feature and usually the remit of confidential peer-review. The reason for confining the meta-analysis to the studies included is not clear. The results are reserved to secondary endpoints. There is considerable variability between the patients studied in each of the six studies used for meta-analysis, in particular in terms of age and baseline VO2max. The authors admit that this study does not provide “information as to whether some adverse responders would revert to a more positive response pattern if exposed to different exercise doses”.

    Thus, in this paper, the raison d’etre for PLoSOne is satisified with extensive discussion about the merits and otherwise of this study occurring in the public forum. However the appraisal does require qualified critique, which was lacking in the commentary provided by much of the lay-press.

  2. About 5% of the population exercises optimally, and is one of our major CV risk factors. The advantages of exercise have been amply outlined by the same authors of the PLoSOne paper previously over the years. It is easy to see how the fast read of the headlines could generate a take-away message to the public that “exercise isn’t always good”, and, consciously or not, decrease their motivation to increase activity, as all current guidelines advise.

    While the benefits of dark chocolate are undisputed, again, when behavior is considered, a take-away that “chocolate is good” can easily result in higher caloric intake. Calculating fat and calorie swaps by the public is hard, and many cannot do it even if they wanted to. They need to hear what they can’t eat first, before being told what should be added.

    There are two ways to treat these papers, with perspective, or narrowly, as John observed. The first would relate what is known and accepted, then the new report placed in proper order. Quantitative statistical comparisons should be made, and this is generally a turn-off for readers. Most likely, audience would be lost because of the length, but it is really needed for the public to decide what to do. Still, there was a bunch of copy about it, and the topic ranks high in both public interest and health.

    An obese diabetic woman confessed she had been eating 3 large bags of chocolate covered nuts weekly after the last report about chocolate. “The chocolate is dark, and nuts are good for you,” she said.

    Eat less, move more is still more likely to produce personal results and reduce risk factors.

    Richard Kones MD

  3. Other studies have shown that to achieve maximum quoted benefits of chocolate, 400-500mg++ of hard stuff are needed for BP, lipid, insulin, and endothelial effects. There is a wide variation in content of commercial cacao and dark chocolates, and this is verified infrequently. All things considered, it has been estimated that the equivalent of 33 bars of milk chocolate or 8 bars of dark chocolate may be needed by Eric L Ding MD at Harvard.

    The calorie and fat equivalents here are so striking that any suggestion that chocolate be used in large populations for any purpose should be confirmed not in mathematical models, but in people out in the real world.

    Richard Kones MD

  4. I share Larry’s scepticism. I think it wise to be cautious in interpreting studies which have measured only intermediate endpoints, or making conclusions from “best case scenario” mathematical modelling.

    Just a side note about compliance though. Larry says “since we’re talking about chocolate I think we’re much more likely to see a problem of over-compliance rather than under-compliance”. I’m not sure if the dark chocolate used in the studies is that tasty. One small pilot study I looked at (http://www.ncbi.nlm.nih.gov/pubmed/19583878) found compliance to be a real problem: “Half of the participants allocated to the chocolate treatment found it hard to eat 50 g of dark chocolate every day and 20% considered it an unacceptable long-term treatment option, whereas all participants found it easy and acceptable to take a capsule each day for blood pressure.”

  5. Stewart Mann, DM (Oxon), FRCP(UK), FRACP says:

    Are the results of the exercise analysis not a statistical inevitability due to the phenomenon of “regression to the mean”?

  6. Most certainly I agree with Dr Montgomery about the unacceptable bitter dark chocolate taste. This is why patients seek substitutes, which are the chocolates which may say “dark,” but contain less polyphenol and more calories.

    I still have serious doubts about the ability of chocolate to “treat” hypertension in a meaningful clinical way, and not simply because of poor adherence. In this instance, call me non-evidence based, but funding a large study to do the RCT is sheer lunacy. Wish it were so.

    Richard Kones, MD

  7. Jean-Pierre Usdin, MD says:

    I think that many people, as I, in a foreign country, never heard of PLoS One (very difficult to write on the keyboard!) but with this cover in Times I think the audience will increase a lot (for some weeks)
    General press is found of these kind of unreliable studies because of the polemic they can rise.
    We had in France about 4 years ago the same “publicity” concerning the cholesterol level and the supposed over use of Statin medications.
    The discussions with some patients were hard and some stopped the hypo cholesterolemic treatment.
    The name of our colleague who started the fire with the Statin in not anymore known by the patients but the storm was important.
    Journalists light the fire and immediately after change for another subject.
    However for us in our private practice the scars are important.
    And in the fight against wrong compartmental habits, the attitude of the news paper directed toward the short term of selling paper is a disaster.
    What pr S Yussuf thinks of that?

  8. Björn Hammarskjöld, M.D., Ph.D. says:

    Still, old knowledge tells us that “exercise improves the appetite”.
    If exercise increases the appetite why should we recommend increased exercise? I think it’s counterproductive to recommend patients to increase their appetite by demanding them to exercise.

    Next question. Why do patients with obesity and diabetes “overeat”?

    The old fashioned physiology gives us the answer.

    Eat 45 g fat (55 g butter) and you your blood glucose level is stable and you are satified and not hungry for four hours.

    Eat 100 g glucose. The blood glucose will rise very quickly to toxic levels, insulin is rising stopping fat conversion to AcCoA and metabolizes glucose to AcCoA to be burned in the mitochondia. As the mitochondia are overloaded with AcCoA the liver will polymerize excess AcCoA to fatty acids and store about half of the glucose as 10 g fat.

    So after 2 h the glucose is all burned up and stored as fat, the glucose level will drop, insulin lever still too high for fat cells to start producing AcCoA as fuel for the mitochondria. So you are forced by the body to have another 100 g glucose to survive for the next two hours.

    So instead of having 45 g fat and stable blood glucose you had to eat 200 g glucose and stored 20 g fat while the blood glucose level rollercasted.

    Summary: Eat nutritious animal fat instead of empty calories of carbohydrates and we will get rid of the obesity and diabetes epidemies.

  9. pam kushner, MA,MD,FAAFP says:

    Excellent answer,I concur