OK, everyone, brace yourselves: a new study shows that potato chips cause weight gain! I’m stunned, people, simply stunned.

Sorry, pardon my slight sarcasm here. It’s been a long day, and I’m also just a bit jaded with studies that state the obvious. But I’m happy to say that this huge NIH-sponsored new study, which rightly made headlines across the world last week after publication in NEJM, offers a lot of excellent evidence-based data on exactly which lifestyle choices actually cause real-world weight loss or gain. We doctors constantly mention lifestyle changes to our patients, but well designed studies like this actually give us some hard numbers. And this prospective cohort study of a huge number of over 120,000 persons offers some of the best data we have. For example:

• Potatoes are bad, in most forms but especially chips. Potato chips caused 1.69 lb weight gain over 4 years, potatoes 1.28 lb
• Sugar-sweetened beverages were next on the list, causing a 1.00 lb weight gain over the 4 year study
• Next were unprocessed red meats (0.95 lb); and processed meats (0.93 lb)

Again, most of the weight gain foods are fairly obvious — but of course, we’ve just discredited the American meat-and-potatoes diet, haven’t we? Well, now we have hard data to persuade people.
I think the most interesting findings were the foods that caused weight loss over the 4 year study:

• Vegetables (−0.22 lb), whole grains (−0.37 lb), fruits (−0.49 lb), and nuts (−0.57 lb) caused weight loss

But here’s what truly surprised me: yogurt was the most effective food to cause weight loss! People who ate yogurt lost an average of 0.82 lb over the 4 years. Wow! This could truly be a game-changer for many people, and I personally plan to add more to my morning diet. The study also looked at other lifestyle factors:

• Physical activity was good, causing 1.76 lb weight loss
• Alcohol use caused a slight increase of 0.41 lb per drink per day
• Smoking caused weight gain (new quitters, 5.17 lb; former smokers, 0.14 lb
• Sleep caused weight gain with <6 or >8 hours of sleep
• Television watching caused weight gain of 0.31 lb per hour per day

Why I’m Jaded

Upon further reflection, I think I was actually initially sarcastic mostly because Americans and people in the West already know most of this, and yet potato chips are hugely popular and we continue to get more obese every year. So here’s yet another study, this time offering real proof — but will it actually change anyone’s habits? So many studies, projects and campaigns have come and gone, and yet obesity ranks continue their incessant climb. And who is mostly responsible for this? Is it a public health/government issue? Should newspapers cover this issue more? Should doctors be posting this in their offices? Or is it ultimately up to each person, who already knows most of this?

This is not an easy answer, and as a public health and community medicine family doctor, I am acutely aware of the misery that obesity is causing my patients. I, like all doctors, desperately wish I could offer a magic pill for everyone to lose weight. At least, in the meantime, I can offer them some new evidence, and here’s my new pitch:

“Dear Patient X, I know we talk about this a lot at our visits, but your weight this time again is a bit higher. We really need to focus again on the weight. But I have some good news — a huge new study proved that eating yogurt daily caused some weight loss! So did nuts, grains, fruits and veggies. The same study also proved that potatoes, especially fried versions like chips, were the worst in causing weight gain. So did alcohol, smoking, TV watching and lack of exercise…So let’s work together for the next 3 months: at least add yogurt to your diet and work on those other foods. Let’s be reasonable and try to lose only 5 pounds a month for now, and I’ll see you in 3 months. I know it’s difficult. but I believe that you can do it; and I promise you’ll be feeling a lot more energetic.”