Diet vs. Exercise: What Counts the Most for Weight Loss?

By Lizzie Streit, MS, RDN, LD  

There are so many different opinions about what contributes the most to weight loss.  

Is it the food choices you make? What about the number of minutes you spend doing cardio? Or the amount of reps you do at the gym? How about those fat-burning supplements and juice cleanses out there? 

You are probably aware that the way to lose and maintain weight is through diet and exercise. But is one aspect more important than the other?  

It turns out that your food choices are probably the most influential factor when it comes to weight loss. You may have even heard the following lines: “you can’t out-exercise a bad diet” or “weight loss is 80% diet and 20% exercise.” These are easy ways to conceptualize the role that diet plays in losing weight, but they are a little ambiguous.  

While exercise can certainly kickstart and enhance weight loss, the foods that you use to fuel your body everyday make a greater impact. Keep in mind that the winning combination is, of course, choosing nutritious foods and exercising regularly. However, if you aren’t sure where to start with your weight loss journey, improving your diet and food choices is a good first step. 

Read on to learn about why diet changes influence weight loss more than exercise, and how to get started with both.  

Why Does Diet Matter So Much?  

To understand the importance of diet for weight loss, you need to recall the basics behind dropping pounds.  

Weight loss occurs when the number of calories you burn is more than the amount you consume. In other words, being in a calorie deficit leads to weight loss.  

Specifically, to lose one pound per week, you would need to be in a deficit of 500 calories per day. This is because one pound of fat equals 3,500 calories. Most people who consume 500 less calories than they burn a day will see weight loss results. 

Achieving a daily 500-calorie deficit is easier to do by changing your food choices than by increasing exercise. This is why you hear so many people say that diet really is more important than activity for weight loss. 

According to the USDA, a large bagel with two tablespoons of cream cheese has approximately 500 calories. If you are used to having this for breakfast, replacing it with foods that have less calories would be one way of eating 500 less calories than usual.   

For example, you could choose a smoothie with vegetables and fruit, plain Greek yogurt with berries, or an egg scramble with veggies. While these foods still contain calories, they would be a step in the right direction if you are trying to cut back on overall energy consumption.  

If you continue to make healthier choices throughout the day, you will reach your desired calorie deficit in no time. Just making simple food swaps or cutting out one or two indulgent foods can decrease the number of calories you consume by more than you even realize.  

Burning 500 extra calories a day through exercise is a different story. According to MyFitnessPal, a person who weighed 150 pounds would have to walk at a brisk pace for 150 minutes to burn 500 calories.  

For most people who have busy schedules, making this type of time commitment to exercise is very challenging. Just getting 30 minutes of activity a day can be difficult. 

So, learning how to make diet changes to decrease calorie consumption is a more manageable task for most people. After all, swapping your potato chips for raw vegetables and hummus is typically an easier, less time-consuming action than exercising for extended periods of time. 

But as you can see, a combination of diet and exercise can get you to your desired calorie deficit more quickly than foods choices or activity alone.  

If you weighed 150 pounds and walked for 30 minutes, you would burn approximately 100 calories. Avoid the bagel and cream cheese with 500 calories in the morning, and you would be cutting out 600 calories a day with those two actions.  

Is it Just About Eating Less Calories?  

Sure, cutting calories leads to weight loss, but can you get away with eating processed foods with tons of sugar and salt as long as your daily calorie consumption is less than what you burn? Not exactly.  

Eating real, whole foods will always be better than choosing highly processed ones. When your diet consists of fruits, vegetables, whole grains, lean proteins, and healthy fats, your body will receive the nutrition it needs to function at its best. When weight loss is your goal, you want your body to be working as well as possible.  

Even more, research shows that the bacteria in your gut may influence weight loss. Poor diet, sedentary lifestyles, and stress can throw these bacteria out of whack. When this happens, it may be more difficult to lose weight.  

Making better food choices is an excellent way to nourish your gut bacteria. Foods high in fiber feed healthy bacteria and might help you rebalance your gut if necessary.  

Lastly, eating foods that are high in sugar but “low calorie” may set you up for cravings and overindulgence. Balanced meals and snacks with complex carbs, proteins, and healthy fats will keep you satisfied and reduce the cravings that make it easy for you to eat more calories than you want.  

What is the Role of Exercise Anyway?  

You may be thinking, “so I’ll still lose weight by changing my diet even if I don’t exercise?” Based on the science behind weight loss, this is true. However, exercise plays an important role in enhancing and maintaining weight loss. Plus, exercise provides so many other benefits. 

Just cutting calories leads to weight loss in the form of protein and fat, whereas exercising leads to more fat loss. This is because activity helps maintain and increase muscle mass, leading your body to burn fat.  

If you start to increase your exercise, you may not see a dramatic change on the scale but your body composition will change. As a result, your clothes might fit better and you may feel skinnier overall. Weight loss that occurs from just cutting calories may not produce the same body composition changes.  

So, to reach your daily 500-calorie deficit more quickly and burn more fat, you will want to make changes to both your diet and exercise routine.  

Keep in mind that exercise isn’t just a way to burn energy. The benefits of physical activity are abundant. Increasing your exercise can lead to better sleep, a decrease in “bad” cholesterol and an increase in “good” cholesterol, improved mood, less joint pain, and more!  

Adding more movement to your day can help you reap these benefits in addition to losing weight. 

How to Improve Diet and Increase Exercise for Weight Loss  

There are several steps you can take to lose weight. For starters, consider logging your daily food intake and activity to see how many calories you consume and burn. This will give you an idea of where to start to achieve a daily 500-calorie deficit.  

Check out this list of apps to help you with this step.  

Next, commit to one or two realistic changes. For example, you may notice that the bowl of ice cream you have every night has 300 calories. Consider cutting this out and exercising for the amount of time it would take to burn 200 additional calories.  

If you aren’t able to exercise every day, consider removing the daily soda you have or swapping potato chips for fresh fruit and vegetables to get to your desired calorie deficit. In addition, make tweaks to your meals to include more plant foods, lean proteins, whole grains, and healthy fats.  

Simply increasing your activity and incorporating more real, whole foods into your diet can certainly help with weight loss. However, most people underestimate the calories they eat and overestimate the amount they burn through exercise.  

Keeping a record of your food and exercise is a much more efficient and exact way to achieve weight loss.  

Making small changes and using an app or food diary to keep track of the energy you eat and burn will help you drop those extra pounds. Over time, these changes will add up and help you achieve your weight loss goals.  

Note from Healthy For Life Meals: Making healthy food choices is the most important aspect of losing weight, but it can be difficult to do consistently. That's where we come in.  When you choose Healthy For Life Meals, you'll know the precise caloric (and other nutritional) content you put into your body each day, so reaching that needed caloric deficit becomes much simpler. Get started with one of our meal plans today. 

Stef Keegan