A healthy diet is linked with greater physical fitness in middle-aged adults, according to researchers from the Beth Israel Deaconess Medical Center in Boston, US. The improvement in fitness observed in participants with better diets was similar to the effect of taking 4,000 more steps each day.
What cardiorespiratory fitness?
Cardiorespiratory fitness reflects the body’s ability to provide and use oxygen for exercise, and it involves the health of multiple organs, such as the heart, lungs, blood vessels and muscles. In fact, cardiorespiratory fitness is one of the most powerful predictors of longevity and health.
While exercise increases cardiorespiratory fitness, it’s also the case that among people who exercise the same amount, there are differences in fitness, suggesting that additional factors contribute.
A nutritious diet is associated with numerous health benefits, but it has been unclear whether it is also related to fitness.
About the study
For the study, researchers examined whether a healthy diet is associated with physical fitness in community-dwelling adults. The study included 2,380 individuals in the Framingham Heart Study. The average age was 54 years and 54% were women.
Participants underwent a maximum effort cardiopulmonary exercise test on a cycle ergometer to measure peak VO2. VO2 is the gold standard assessment of fitness and indicates the amount of oxygen used during the highest possible intensity exercise.
Participants also completed the Harvard food frequency questionnaire to assess intake of 126 dietary items during the last year ranging from never or less than once per month to six or more servings per day. The information was used to rate diet quality using the Alternative Healthy Eating Index (AHEI) and Mediterranean-style Diet Score (MDS), which are both associated with heart health.
Higher scores indicate a better quality diet emphasising vegetables, fruits, whole grains, nuts, legumes, fish and healthy fats and limiting red meat and alcohol.
The researchers evaluated the association between diet quality and fitness after controlling for other factors that could influence the relationship, including age, sex, daily calorie intake, body mass index, smoking status, cholesterol level, blood pressure, diabetes and routine physical activity level.
Higher diet quality associated with improved fitness
Compared with the average diet quality score, an increase of 13 points on the AHEI and 4.7 on the MDS was associated with a 5.2% and 4.5% greater peak VO2, respectively.
In middle-aged adults, healthy dietary patterns were strongly and favourably tied to improved fitness even after taking habitual activity levels into account. The relationship was similar in women and men, and more pronounced in those under 54 years of age compared to older adults.
How can diet impact fitness level?
To discover how diet might boost physical fitness, the researchers performed further analyses. They looked at the relationship between diet quality, fitness and metabolites, which are small molecules produced during digestion and released into the blood during exercise.
A total of 201 metabolites (e.g., amino acids) were measured in blood samples collected in a subset of 1,154 study participants. Some 24 metabolites were associated with either poor diet and fitness, or with favourable diet and fitness. The lead researcher said, “our metabolite data suggest that eating healthily is associated with better metabolic health, which could be one possible way that it leads to improved fitness and ability to exercise.”
This was an observational study and does not prove that eating well causes better fitness, or exclude the possibility that fit individuals choose to eat healthily
Source: European Journal of Preventive Cardiology, May 15, 2023.
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