Department of Research & Evaluation News

Physical activity and cardiorespiratory fitness may be more strongly associated with living longer than diet quality, according to a new review co-authored by a Kaiser Permanente physician.

The review, published in Mayo Clinic Proceedings, compared decades of research on diet quality, physical activity and cardiorespiratory fitness to determine how strongly each was associated with the risk of death from all causes. The researchers found that physical activity and fitness consistently showed stronger associations with lower mortality risk than diet quality.

“This analysis compares the relative benefits of eating a healthy diet with doing regular exercise on mortality rates,” said senior author Robert E. Sallis, MD, a family medicine and sports medicine physician practicing at the Kaiser Permanente Fontana Medical Center. “Our review of the evidence clearly shows that both diet and exercise are important for living longer but doing regular exercise lowers mortality more than eating a healthy diet. I see many patients who have a normal BMI but are not healthy. However, it’s hard to find a patient who exercises regularly and is physically fit but is not healthy.”

Comparing diet and physical activity

Sallis and lead author Glenn A. Gaesser, PhD, of Arizona State University, reviewed peer-reviewed research identified through PubMed, prioritizing meta-analyses and large prospective studies and, when possible, studies that objectively measured physical activity or directly assessed cardiorespiratory fitness.

One of the biggest differences emerged when the researchers compared the risks associated with poor diet and inactivity. Across the studies reviewed, poor diet quality was associated with a 3% to 20% higher risk of death from all causes. By comparison, the most sedentary people had a 46% to 163% higher risk.

The researchers also found stronger associations when looking at healthy behaviors. Healthy dietary patterns and foods were associated with a 4% to 23% lower mortality risk, while higher levels of physical activity were associated with reductions as great as 67%. High cardiorespiratory fitness was associated with a 41% to 53% lower risk.

Small increases in activity may make a difference

The findings suggest people do not necessarily need dramatic changes in their exercise habits to potentially benefit.

Adding about 2,000 steps a day, roughly equivalent to walking a mile or about 20 minutes, was associated with a 23% to 49% lower risk of death from all causes. Among the least active people, adding just 5 minutes of physical activity per day was associated with a 30% lower risk, while 10 additional minutes was associated with a 42% lower risk.

The review also examined studies in which diet and physical activity or fitness were considered together. While people with both a healthy diet and high physical activity or fitness generally had the lowest mortality risk, those who were highly active or fit but had lower diet quality generally had lower mortality risk than those who ate healthier diets but had low activity or fitness.

Both diet and exercise remain important

The researchers emphasized that the findings should not be interpreted to mean that eating a healthy diet is unimportant. Instead, they suggest that physical activity and fitness warrants greater attention alongside nutrition in efforts to improve health and longevity.

The review also has limitations. Much of the evidence came from observational research, which can demonstrate associations but cannot establish cause and effect. Studies also varied in how they measured diet quality, physical activity and fitness, making precise comparisons difficult.

Still, the findings offer an encouraging message for people who may find changing their diet difficult: becoming more active may provide meaningful health benefits even when other lifestyle habits are less than ideal.