You’ve probably heard that “you can’t out-exercise a bad diet.”
While this saying has some merit, you may wonder whether diet or exercise is more important for health goals like weight loss or improved heart health.
With endless health interventions out there, ranging from the 80/20 rule to exercise-free diets, it can be hard to gauge if you should prioritize diet or exercise — or if the answer lies somewhere in between.
This article tells you the benefits of exercise and diet, and if one is more important for your health than the other.
To lose weight you must be in a calorie deficit, meaning your body expends more calories than you consume. This can be achieved by eating and drinking fewer calories, burning more calories from physical activity, or a combination of the two (1).
Benefits of diet
While both diet and exercise are important for weight loss, it’s generally easier to manage your calorie intake by modifying your diet than it is to burn significantly more calories through exercise.
This may be why the 80/20 rule has become popular, as it states that weight loss is the result of 80% diet and 20% exercise.
For example, if you’re aiming for a daily calorie deficit of 500 calories, you could consume 400 fewer calories (80%) by eating lower calorie dishes, smaller portion sizes, and fewer snacks. Then, you only need to burn 100 calories (20%) from exercise.
For many people, this is easier than trying to burn 500 calories each day from exercise. Burning this many calories every day requires a significant amount of movement — plus, it’s time-consuming, taxing on the body, and rarely sustainable.
To illustrate, a person who weighs 154 pounds (70 kg) would need to cycle on an exercise bike for 1 hour at moderate intensity to burn 525 calories. Meanwhile, they could cut out 520 calories by skipping out on a venti Green Tea Frappuccino from Starbucks (2, 3).
Benefits of exercise
There are many ways that exercise supports weight loss.
Strength training helps preserve and build muscle mass, which can increase your metabolic rate over time so your body burns more calories, even at rest. Furthermore, a single strength training session can increase your metabolic rate for up to 72 hours (6, 7, 8, 9).
Aerobic exercise such as walking, jogging, or cycling — especially at a low to moderate intensity for 30 minutes or longer — can burn a significant number of calories in a single session and help promote a calorie deficit (10, 11, 12).
Regular exercise may also help manage hunger by regulating your hunger hormones. This may help prevent overeating and excess snacking. That being said, excessive exercise may increase appetite as well as injury risk, so moderation is best (13, 14, 15, 16).
Finally, by burning extra calories and increasing your metabolic rate, regular physical activity allows you to have more flexibility with your diet, making weight loss more enjoyable and less restrictive (17).
Recommendation: Combination of diet and exercise
Although the 80/20 rule is a helpful guideline, you don’t have to follow it precisely. Instead, focus on making positive changes to your diet and exercise routine that work for you.
For instance, you may prefer achieving your daily calorie deficit 50% from diet and 50% from exercise. This means you’ll spend more time and energy exercising — but in return, you won’t need to limit your food intake as much.
The key for healthy, long-term weight loss and management is to use both diet and exercise (5).
In fact, one review showed that combining modest calorie restriction and exercise was the best way to achieve significant weight loss. In some cases, combining the two led to over five times more lost weight compared with using exercise alone (18).
Similarly, another review found that weight loss programs including both diet and exercise components had significantly greater weight loss results than interventions based on changes to either diet or exercise alone (19).
Ultimately, combining dietary changes and regular exercise can help you achieve more meaningful and sustainable weight loss in the long term.
While it may be easier to manage how many calories you consume, regular exercise helps preserve lean muscle and burn additional calories. Therefore, both diet and exercise are important for weight loss, and combining the two will optimize results.
Both exercise and diet play significant roles in heart health.
Benefits of diet
The foods we eat can support or hinder heart health.
The dietary patterns associated with reduced heart disease risk are centered around minimally processed vegetables, fruit, whole grains, healthy fats, and lean animal and plant-based proteins while being low in sodium (20, 21, 22, 23).
For example, the well-established Mediterranean diet promotes heart health. It’s high in healthy unsaturated fats from olive oil, fish, and nuts, dietary fiber from whole grains and vegetables, and antioxidants that help fight harmful molecules called free radicals (24, 25, 26, 27).
The Dietary Approaches to Stop Hypertension (DASH) diet is another evidence-based eating style similar to the Mediterranean diet.
Diets high in saturated fats, sodium, added sugars, and refined carbohydrates from processed and red meat, sugar-sweetened beverages, baked goods, and highly processed snack foods like chips are linked with a higher risk of heart disease (27, 31).
Benefits of exercise
Numerous studies have shown that exercise can help lower your risk of heart disease, decrease blood pressure and LDL (bad) cholesterol levels, increase your heart’s size and strength, and improve cardiorespiratory fitness (32, 33, 34).
Even if you don’t lose weight, you may experience these benefits when exercising regularly.
Moderate to high intensity cardio exercise strengthens the heart, allowing it to push more blood into your body with each heartbeat. This decreases the amount of stress on the heart and arteries, which lowers the risk of heart disease (32, 33, 34).
General recommendations include getting either 150 minutes of moderate intensity exercise, 75 minutes of high intensity exercise, or a combination of the two each week for optimal heart health (32).
Even a low intensity aerobic activity such as walking may reduce your heart disease risk (32).
Keep in mind that if you have heart disease or another chronic condition, you should speak with your healthcare professional before starting a new exercise program.
Recommendation: Combination of diet and exercise
Other lifestyle changes that improve your heart health include quitting smoking, limiting or eliminating alcohol, maintaining a weight that is healthy for your body, and managing stress (38, 39, 40, 41).
Consuming a minimally processed, whole-food diet rich in healthy fats, fiber, and lean protein is linked to better heart health. Along with this, regular exercise keeps your heart stronger and reduces certain risk factors for heart disease.
Diet and exercise can play important roles in other areas of your health, too.
To build muscle, you need to do resistance training with progressive overload and eat enough protein throughout the day.
If you don’t challenge your muscles through resistance training, you won’t build muscles simply by eating a high protein diet. Likewise, if you do engage in strength training exercise but don’t consume enough protein, it will be difficult to gain muscle (41, 42, 43).
Therefore, both diet and exercise are important for building muscle.
Exercise can also provide both immediate and long-term benefits to mental health. It promotes the release of mood-boosting endorphins — such as dopamine, serotonin, and norepinephrine — that temporarily improve your mood and stress levels (48, 49).
In addition to any treatment recommended to you by your healthcare professional, regular exercise and a nutritious diet may improve your mental well-being.
Both diet and exercise have been shown to promote muscle building and improve mental health.
Diet and exercise are both important for optimal health.
Achieving a calorie deficit through diet modifications is key for weight loss, while exercise provides many benefits that help sustain your results.
Further, both exercise and diet can help reduce heart disease risk, build muscle, and improve your mental health.
To promote good overall health, it’s best to consume a minimally processed, whole-food diet full of healthy fats, fiber, and lean protein. Also, aim to get at least 150 minutes of moderate to vigorous exercise each week.
While you may be tempted to pick one over the other, diet and exercise work hand in hand, and combining both will optimize health and quality of life.