You may have heard about the New England Journal of Medicine study published this week by Harvard researchers and widely reported in media outlets: Changes in Diet and lifestyle and Long-Term Weight Gain in Women and Men.
Many of my patients were confused when reading the newspaper articles covering the study. Reporters seem to be latching on to potatoes and anything made from them (eg, French fries, chips, etc) as the “dietary devil” because people who tend to eat these foods were, in this study, likely to gain the most weight over the past 2 decades.
Be careful. This is the wrong conclusion to draw from this study. While potato chips and fries aren’t health foods, this type of study – called a cohort study – can’t make definitive conclusions about what’s healthy or not. Rather, the conclusion to draw might be: people who tend to eat lots of fries or chips also tend to gain more weight than others. Is it the potatoes? Maybe. Is it that people who tend to eat these comfort foods also tend to eat other comfort foods, and perhaps eat less healthy foods, and perhaps exercise less, and perhaps have lower incomes, and the like? Possibly.
The fact is that we don’t know, and this study can’t tell us – nor is it designed to tell us. Rather, it gives us “hints” that we have to follow up with other studies over time. It is important to measure our responses to any study so that we avoid jumping to conclusions that aren’t true.
While this may not seem particularly worrisome, it can be. For one, it would be a shame if people jump on yet another fad diet bandwagon….”the no-potato diet,” anyone?! Second, I think this creates even more confusion when it comes to nutrition; yet another confusing, contradictory admonishment that makes it even more difficult for us to know what to do when it comes to managing our health and our weight.
Remember when the media reported several years ago that vitamin E was a miracle pill?? And then a couple years later they reported that newer studies show it doesn’t actually do anything?? Same deal. The initial studies were cohort studies. An appropriate conclusion to these were that people who take vitamin E pills tend to have less heart disease than those who don’t. But, we didn’t know from the initial studies whether the vitamin E was the reason, or whether people who take vitamin E pills also do other healthy things that benefit their hearts – exercise, eating healthy, and the like. Later studies confirmed that it’s not the E, it’s the overall healthy lifestyle. But the latter doesn’t make for a good front-page story.
As always, caveat emptor…especially when it comes to nutrition, unfortunately.