OPINION:
Before I begin, I need to declare my Washington bias, as I greatly enjoyed my two years as a visiting associate at the National Institutes of Health in Bethesda, Maryland. After my return to Linkoping University in Sweden, my former supervisor, Michael J. Quon, contacted me, having seen the documentary “Super Size Me” by Morgan Spurlock. He asked whether I would carry out a scientific version of Spurlock’s “study.”
Having great respect for Mr. Quon, I agreed.
I would emulate the conditions laid out in the documentary as closely as possible with a single goal in mind: Trial participants should increase their weight by doubling their daily calorie intake on a fast-food diet and avoiding all exercise for four weeks.
Many of my male medical students wanted to participate. (After all, they were promised free fast food and other reimbursements.) Yet to get the approval of the university’s ethical review board, I needed to include women too. Though it was indeed difficult to find female volunteers who were healthy mentally and physically, and willing to gain weight just in time for the short Swedish beach season, in the end, we got six girls. With our 12 guys, we had 18 people in the study.
This fast-food trial resulted in many controversial findings. For example, three of the participants increased their resting energy expenditure by 30%, corresponding to an ability to burn off at least one of the extra Big Macs per day. I also found that those who turned to sugary drinks to meet the caloric intake goal got even worse liver lab tests than Spurlock reported (tenfold increases).
On the other hand, those who consumed lots of saturated fat were rewarded with the highest HDL cholesterol increases. (That’s the healthy cholesterol variant, which cleans your blood vessels.)
Based on the many findings from this fast-food adventure, my colleagues and I followed it up with a two-year trial on diabetic patients. In that one, we put participants on one of two diets: either a low-carb plan or the traditionally recommended low-fat plan. Each group showed weight reductions of nearly 9 pounds, but it was only those randomized to the low-carb diet who showed improved glucose levels, reduced abdominal obesity and reduced low-grade inflammation while requiring less insulin.
Later on, I tested the “All exercise is good” theory. For that, I recruited students who ran 5 kilometers most days. I then compared them on their running days with them on days they sat doing homework at our clinic.
What did I find?
Most participants had higher insulin and glucose levels after running, and their races induced strong laboratory signs of heart-muscle deterioration.
Other researchers have since demonstrated, by MRI, prevalent myocardial scarring in the hearts of marathon runners. In fact, the scarring was found to be three times more common among these runners than it was in couch potatoes.
I describe these and other side effects of so-called “healthy lifestyles” in my book “Lighten the Load on Your Shoulders!”
In a recent Swedish TV4 interview after the Gothenburg half marathon (in which three heart attacks had occurred) the reporter asked what I would tell runners planning to do the then-upcoming Stockholm Marathon. I responded that they were risking heart attacks and that endurance races are well-known sources of dose dependency for atrial fibrillation because of scarring and enlargement of the heart.
This interview apparently induced some sadness among many TV viewers. A cardiology professor requested an on-air debate, during which I pointed out the elephant in the room: If these races are so healthy, why are ambulances waiting all along the track?
Unfortunately, my warning failed to prevent an additional three heart attacks during the Stockholm Marathon of 2025.
Recently, I also took on the health issue of smoking or “snusing” tobacco. Just 5% of Swedes are now smokers, so Sweden is considered smoke-free by the World Health Organization. Still, this doesn’t mean we aren’t ingesting nicotine. In Sweden, we have a tradition of putting nicotine-containing pouches under our upper lips.
Still, Swedish health care professionals urge such nicotine users to quit because “all nicotine is bad,” right?
Maybe not.
My research as a professor and consultant in internal medicine has led me to believe that it is the smoke that harms smokers and bystanders. (I have also noticed that nicotine pouches are sold at the university hospital pharmacy, where I work.)
To test whether you really get benefits after quitting nicotine, we recruited 50 or so people for a prospective trial. We got a 74% quit rate for three months, and guess what. We found no positive health effects from quitting the use of snus. Still, we did find that quitters experienced an average weight gain of nearly 4½ pounds and home blood pressure test increases of 4 mm Hg.
Not one of the measured risk parameters improved.
However, nicotine and endurance sports (and alcohol and coffee) have a commonality: They can all be addictive.
Here’s another common addiction that’s not nearly as good for you as you think it is: breakfast.
Many people I know feel stressed without breakfast. They think they need it to get their days started. Still, the only large, randomized lifestyle trial that has substantially reduced cardiovascular disease (by approximately 30%) was breakfast-free. It was called the PREDIMED trial, and it put participants on one of two diets: the Mediterranean diet, which traditionally does not include breakfast, and a low-fat diet. The Mediterranean dieters were asked to drink wine with meals, and they were the ones who showed the drop in cardiovascular disease risk.
Indeed, I have even published that daily intake of wine lowers cholesterol, glucose and the hunger-inducing hormone ghrelin.
In summary: If you feel happier and more focused when you drink coffee or use snus, do it. It will enhance your life. Remember that breakfast-free Mediterranean food with wine for dinner reduces your risk of heart attacks.
Also, be aware that if you are addicted to endurance sports, you might run through the gates of heaven faster than anticipated if the ambulances aren’t ready.
• Fredrik H. Nystrom is a professor of internal medicine and endocrinology at Linkoping University in Sweden and the chief internal medicine physician at his clinic. He is also the author of “Lighten the Load on Your Shoulders!”
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