This Week In Medicine: 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 of serious cardiovascular events like heart attacks and strokes by eating dar chocolate every day.

Let’s take a quick look at each study:

The exercise study used data from 1,687 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 exercising.

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 1,000 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 ommission.

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 how they contribute to public health.


  1. dearieme says

    I’d like to know why everyone recommends exercise if “We do not know whether implementing exercise programs for unfit people assures better outcomes. That has not been established.”

  2. Kevin Lomangino says

    Expanding on your comment about the lack of public health significance for these findings, I have to ask: Is it time for a moratorium on further research regarding chocolate and CVD? We already know that eating a small amount of dark chocolate daily seems to nudge risk markers in the right direction and probably won’t cause harm. But as you say, few people really believe that chocolate has an important role to play in the metabolic syndrome or CVD prevention. The only way to make us believe would be a big outcomes study, and I think the chances of that study ever being conducted are low. And while we wait around for that study that probably won’t happen, I’m sure there’ll be no end to the epidemiologic studies, modeling studies, and other reports suggesting (but never proving) that chocolate prevents heart attacks. These studies all have tremendous flaws, including, in this case, the fantastical assumption that adding a daily 100g dark chocolate bar to your diet — about 600 calories (!) according to the USDA nutrient database — for 10 years won’t cause weight gain or other adverse effects that might counterbalance the so-called benefits.

    These reports are nice padding for the CVs of the academics who publish them, and they must generate a decent amount of traffic for journals and the media. The chocolate companies must also be loving all this attention. But from a public health perspective, is there any point to continuing on a road that seems to lead to a dead end? At best it seems like a distraction from more promising lines of research. And at worst, the message that’s getting out to the public – “Chocolate is good for you!” – may be digging us further into an obesity hole that we’re desperately trying to climb out of.

  3. Robert Weitz says

    These studies are simply headline/grant grabbers. They are the kind of thing people read and don’t scrutinize because they are easy to accept and adhere too.

    I had a mixoma removed from my heart and am supposed to have severe CHF along with AF. I live with no-symptoms and have low LDL without statin drugs because of healthy diet and hard regular exercise. I do eat a little high cocoa/ low sugar chocolate.

    The studies are paid for by someone and they always look for results that benefit their interests. Follow the money and you will find why a researcher focuses on the data that suits them.

  4. Andrew Holtz says

    Several of the underlying studies had control arms. Is it indeed the case that this analysis didn’t bother to look at the data from those control groups to see if non-exercisers did better or worse than those who completed exercise programs?

    Why didn’t they make that comparison? And without such a comparison what possible use is this study?

  5. Each day I have a cup of cocoa tea, which I make by stirring about 2-3 teaspoons non-dutched cocoa powder into a cup of hot water. No sugar, tiny amount of fat. No dairy added because some studies have shown that milk proteins bind to the flavonoids in cocoa, limiting their absorption; other studies haven’t supported this. My cocoa tea sounds awful but to me it’s like black coffee.

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