Diet vs. Exercise: Which is More Important for Weight Loss?

Author: Karen Tickner, BS, NCPT, MES

If you ask a bodybuilder how to get a six-pack, they will tell you that “abs are made in the kitchen.” In other words, they say that in order to see their abs, they focus more on their nutrition than their crunches. For those of us who are trying to lose weight and maybe get a little bit of muscle tone, this idea could sound a little backwards. Wouldn’t exercise make you see your abs? That’s a very good question. What really is more important on your weight loss journey: diet or exercise?

First thing’s first: Exercise is important

Exercise is important, and we all need physical activity to keep our bodies healthy and live longer, fuller lives. Regular exercise has a myriad of benefits including: increased stamina and strength; stronger heart and lungs; better flexibility; stronger bones; improved blood sugar, blood pressure, and cholesterol; and improved moods — and that’s just naming a few! 

One of the biggest impacts that exercise has on your weight loss journey is that it can preserve (and build) muscle mass. This is important since muscle mass is more metabolically active than fat mass (meaning that muscles uses more energy (calories) even at rest). In short, having more muscle helps increase your metabolism (the number of calories you burn in a day), which in turn helps you keep your weight loss off!

However, it’s using exercise to lose weight in the first place that has us asking about its effectiveness.

Now, let’s do some math!

Simply, losing weight is a math problem. In order to lose weight, you must create a caloric deficit. Basically, you’re spending more calories than you are taking in. Sounds pretty straightforward, right? And exercise should help you reach that deficit too, right? Well, the answer isn’t that easy. The human body is a complicated machine, and human behavior is even more complicated. 

First of all, how many calories you burn each day (aka your TDEE or total daily energy expenditure) is made up of four main parts: your basal metabolic rate (the calories you need to keep your body running), the energy you use in breaking down food, the energy you burn from non-exercise related mechanisms like didgeting, and physical activity. Physical activity usually only makes up about 10-15% of the calories you burn in a day.

If you’re looking to 1 lb per week, your goal would be to create a deficit of 3500 calories per week. That means that an average person must create a deficit of 500 calories per day by eating less food, burning more calories through activity, or a combination of the two. 

Now let’s look at an example: a person who weighs 185 pounds would burn about 200 calories walking 30 minutes at a quick pace. So of the 500 calories deficit you need, a 30 minute walk could contribute to 200 calories.

Now, here is where the food balance comes into play. An average total daily energy expenditure (TDEE) is right around 2000 calories per day. However, according to the Food and Agriculture Organization of the United Nations, the average American’s diet is higher than 3500 calories per day, meaning many people are actually gaining weight slowly over time. In this case, the average person would see benefits from exercise, the caloric deficit needed for weight loss wouldn’t be enough.

If you’re seeking to lose weight and decide to make changes to your diet (eating more low calorie-dense, nutrient-rich foods, replacing calorie-rich drinks with water, eating fewer processed foods, etc.), it’s a lot easier to create a calorie deficit necessary for weight loss, even without exercising. For example, if you replaced your morning latte with tea, enjoyed one scoop of ice cream instead of two, and ordered a side salad instead of french fries with your sandwich, you’d have saved over 600 calories!

The bottom line

Though we’d all like to say that we could just “work it off” at the gym, the truth is that we really don’t burn enough during exercise to make that happen. But if you want to lose weight, eating healthy on a lower calorie budget is an easier way to create the deficit that you need to achieve weight loss. It is important to note that incorporating activity into your routine will likely enhance your results and help you keep the weight off long-term, and is worth incorporating into your routine for all the other awesome benefits.

Simply stated, if you want to see weight loss, changing your eating habits is a much stronger and more effective way to make that happen, especially at the beginning!