What’s more important: Diet or exercise? Here’s the research

By Alistair Gardiner
Published October 12, 2020

Key Takeaways

Almost everyone aspires to eat more nutritionally, work out regularly, and become the best and healthiest versions of themselves. Unfortunately, life doesn’t always provide the time or motivation required to improve every aspect of our health.

So, what should we prioritize: paying more attention to our diets, or focusing on scheduling more exercise into our routines? The answer is complicated, but here’s the scientific community’s best estimate, based on the evidence.

Is it how much we’re eating, or what we’re eating?

It’s common knowledge that obesity increases the risk of developing dozens of health problems. Over the years, study after study has found that a high body mass index (BMI) is linked to higher rates of all-cause mortality, too.

That’s especially troubling when considering that in the past four decades, obesity rates have doubled in more than 70 countries and steadily increased in almost every country across the world. In 2015, high BMI was found to be the cause of 4 million deaths globally, with more than two-thirds of those deaths due to cardiovascular disease.

It may seem that the solution to this problem is simply weight loss, but a new study has found that the types of food that we’re eating may be more important than simply lowering BMI.

The study, which was published in PLOS Medicine, investigated whether eating a Mediterranean-style diet affects mortality for individuals at different levels of BMI.

Over a 21-year period, researchers collected data on nearly 80,000 adults. The study not only looked at each individual's BMI, but also considered variables like age, educational level, marital status, leisure time, physical exercise, and smoking habits. Notably, it looked at the extent to which each person’s food choices matched up with a Mediterranean-style diet, which emphasizes vegetables, fruits, fish, nuts, unrefined grains, and fermented dairy products.

Results suggested that individuals who adhered to a Mediterranean diet and were overweight—but not obese—had the lowest rates of all-cause mortality. Surprisingly, these individuals were found to be at an even lower risk of all-cause mortality than those with a healthier BMI who ate a Mediterranean diet. The results were similar for cardiovascular disease-based mortality; those who complied best with a Mediterranean diet—even those with a high BMI—tended to have lower mortality than those with a less healthy diet.

Of course, there are a number of factors at play here. The authors note that overweight people appear to be less likely to exercise, a variable that may skew the results somewhat. But regular exercise seems to be just one of many characteristics of people with an average BMI, so it’s unclear whether exercise is any more important than several other risk-lowering factors, like attaining a higher level of education, according to the results.

This is not the first study to suggest that a Mediterranean diet may be associated with lower disease and mortality rates. A number of other studies have shown that these types of diets appear to lead to lower risks of cardiovascular disease, and lower risks of all-cause mortality.

The results of some of these studies suggest that a diet like this can lead to health benefits like reduced blood pressure, lower inflammation and lipid levels, and improved metabolism.

While all of these studies suggest that following a healthier diet offers a number of benefits, none concluded that a healthy diet is the only, or even the best, way to mitigate your likelihood of developing cardiovascular disease or lengthening your life. So, how about exercise?

Can exercise salvage a bad diet?

While diet may be a more important factor than body weight, that doesn’t mean exercise isn’t equally, if not more, important in keeping healthy and living a longer life.

According to an article published in the Journal of Psychopharmacology, cardiorespiratory fitness (CRF) is not only a major diagnostic and prognostic indicator of health and mortality, but it may be more significant than factors like hypertension, diabetes, smoking, or obesity.

The article cited evidence from a number of different studies that suggested a moderate or high level of CRF reduces the risk of all-cause and cardiovascular disease mortality regardless of other factors like age, BMI, and other health conditions.

“It does seem likely that individuals can reduce their risk of mortality by improving CRF, regardless of their level of adiposity,” the authors concluded.

One of the studies they cite found that exercise capacity “is a more powerful predictor of mortality among men than other established risk factors for cardiovascular disease,” including BMI.

Another study, which analyzed the health of over 334,000 individuals, found that twice as many deaths could be attributed to a lack of physical activity than those attributed to obesity. The authors even suggest that the equivalent of 20 minutes of brisk walking per day could be the key to reducing the chance of an early death.

A balanced life in a ‘Blue Zone’

So, what should we focus on to live our healthiest life? Is working out the key? Or should we prioritize a healthy diet? The answer may be found in the lifestyle balance practiced by those who inhabit Blue Zones.

The term Blue Zone was brought into the mainstream by reporter Dan Buettner in an article titled “The Secrets of Longevity,” published in National Geographic. Buettner’s reportage was based on a number of studies that identified several places with an above average number of centenarians. These areas include the Italian island of Sardinia, the Japanese island of Okinawa, and Loma Linda, California.

While the studies suggest that genetics may factor into the longer life expectancy of the inhabitants of Blue Zones, they also found that these inhabitants shared a number of lifestyle traits that likely contributed significantly to their longevity. These include eating a largely plant-based diet, engaging in regular physical activity, a relative lack of smoking, and staying socially connected with their respective communities.

Bottom line

While one study released this year refutes the Blue Zone hypothesis—positing that fraud, error, and a lack of birth records leaves the claim disputable—most of the studies cited above strongly suggest that a combination of healthy diet and regular exercise is your best bet.

But for people who lack the time or willpower to maintain a healthy regimen of diet and exercise, keep in mind that the evidence suggests that the risk factors inherent in higher BMI can be mitigated by either approach.

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