When trying to lose weight, what is the first form of exercise that comes to mind for most? If you said running, you would be correct. As runners we are proud of our sport, and we love to reap the rewards of our hard training and dedication to getting faster by indulging in some rewards after the race is complete. We are told to eat healthy, and usually runners are pretty good at this, but when you are at that point in your training where the mileage and intensity are high, it can be tempting to get into the mindset of being able to eat whatever you want, as you will burn it off in that 20 miler you have coming this weekend. Runner and author John L. Parker Jr. once wrote that “if the furnace was hot enough, anything would burn, even Big Macs”—meaning that distance runners could, if they ran enough, eat pretty much whatever they wanted and stay healthy and lean.

Does running give you a free pass to eat anything you like?

An editorial published last month in the British Journal of Sports Medicine explicitly and sharply critiqued that viewpoint, arguing that, as its title states, “you cannot outrun a bad diet.” The authors, Aseem Malhotra, Tim Noakes (who was interviewed on our podcast last year), and Stephen Phinney, argued instead that the key to weight loss and overall health is a low-carbohydrate diet, not exercise.¹ The editorial went on to criticize the food industry for marketing sugar-laden products while supporting the message that exercise is the best path to weight loss and health. They cited a number of recent scientific studies in support of their argument, including one which showed no significant change in physical activity levels over the last thirty years, despite obesity rates spiraling higher.

Now: This puts runners in an uncomfortable position. Traditionally, we’ve relied on our prodigious exercise volume to counteract our carb-heavy and often less-than-perfect diets (post-race pizza and beer, anyone?). If Malhotra, Noakes, and Phinney are correct, runners might need to rethink their approach to maintaining good overall health.

Is a healthy diet more important than exercise?

The BJSM paper attracted a horde of media attention, spurring articles with titles like “Exercise ‘not key to obesity fight,’” but it also raised some eyebrows among fellow medical doctors and public health researchers. The reaction among experts was a mixture of cautious endorsement and stern criticism.

Here’s the deal: On one hand, Ian Broom of the Centre for Obesity Research and Epidemiology at Robert Gordon University in Scotland said in an interview that he tends to agree with the paper’s point that high-carb diets promote insulin resistance (a precursor to type 2 diabetes), and that exercise does not have a significant contribution to weight loss, though he pointed out a few misconceptions in the paper.² On the other, in a commentary for a group called the Global Energy Balance Network, Steven Blair, a professor at the University of South Carolina, criticized Malhotra, Noakes, and Phinney’s interpretation of the data analysis, and Nicholas Finer at University College London claim the paper’s authors confused correlation with causation in many of their examples.^{3, 2} This is interesting: When the BJSM temporarily retracted the paper because of “an expression of concern,” it only added to the controversy. According to Retraction Watch, a website that reports on scientific papers that are withdrawn, the retraction occurred because of some undeclared conflicts of interest from the authors, though there were also grumblings about claims made from tenuous evidence.⁴ Being transparent about potential competing interests that might bias your results is one of the cornerstones of scientific research. In this case, the BJSM reinstated the paper after it was made clear that two of the authors have written popular books extolling the benefits of low-carb diets, and one is a paid member of the Atkins Scientific Advisory Board (of Atkins Diet fame).

Exclusive bonus: Get the only runner’s calorie calculator that factors in your metabolism and the miles you ran to help you determine exactly how many calories you burned each day. Plus, get a breakdown of how many calories you need to eat (including how many carbs, proteins and fats you should target) to lose weight. Download yours for free here.

It’s important to note that this does not invalidate their research; in fact, it’s far from the only potentially confounding interest in this story.

Steven Blair’s Global Energy Balance Network, which criticized the study, is funded in part by The Coca-Cola Company, and another health expert who publicly criticized the article had previously given paid talks on behalf of a fruit juice company.

What does this mean for “you can’t outrun a bad diet”?

The good news is that there are a few points of agreement among researchers. Even Malhotra, Noakes, and Phinney admit at the beginning of their article that moderate to vigorous exercise decreases your risk of heart disease, cancer, type 2 diabetes, and dementia. And some critics of the study pointed to a large meta-analysis published last year that found, while including exercise in a weight-loss program does lead to better long-term results than only dieting, it does not lead to more weight loss in the first several months of a program.⁵

Conclusion

But the real question, which may remain muddled for a while longer, is whether exercise can counteract the effects of poor dietary decisions. On top of this, it’s not quite clear what exactly constitutes poor dietary decisions! Does the very high carbohydrate turnover of a runner in training offset potential health risks (if there are any) of eating a lot of carbs in your diet? You can probably guess what the soft drink industry and low-carb dietary institutions think the answer to that is, but uncovering the real truth will likely take several more years of patient, careful, and rigorous research. As that process unfolds, it’s probably best to follow that old adage of “all good things in moderation.” It’ll be a while longer before we have any good answers on whether a lot of exercise negates a bad diet, so for now, better to hedge your bets and lean towards a healthy diet, even if you do run a lot.

Struggling with your weight?

Losing weight is one of the primary reasons many runners begin the sport, although most runners then fall in love with the other benefits running brings, but what if you are struggling with weight? Can we remind you that you are not the only one! Not only does almost every runner worry about their weight in some way, but many runners even gain weight shortly after starting their training!

Check out our previous posts about weight for more information, and to hopefully put your mind at ease!

• Why You Might Gain Weight While Training For The Marathon
• How Much Does Excess Weight Impact Your Running Performance?
• Why You Might Not Lose Weight While Running
• Losing Weight Without Sacrificing Running Performance
• Understand How Metabolism Works to Unlock the Mystery of Running and Weight Loss

If you want to keep better track of your calories, check this out:

Exclusive bonus: Get the only runner’s calorie calculator that factors in your metabolism and the miles you ran to help you determine exactly how many calories you burned each day. Plus, get a breakdown of how many calories you need to eat (including how many carbs, proteins and fats you should target) to lose weight. Download yours for free here.