Diet vs. Exercise: What Matters Most For Weight Loss? [Science]

May 24, 2021Dr. Grant Radermacher

“Eat Less, Move More!”

It’s an easy maxim to spout off. Losing weight is simple, right? Just ration the calories you’re consuming and get to the gym for a few hours of weightlifting and cardio every day. Repeat tomorrow. And the next day. And so on.

Unfortunately, blanket recommendations like the one above completely sidestep the one factor that matters most: practicality.

Yes, we should all eat healthier. Yes, exercise should be a non-negotiable part of our week. There are infinite things we should do in order to keep our bodies functioning optimally – sitting less, eating more vegetables and less processed food, drinking less alcohol. But they don’t take into account the reality of life: we’re all constrained by a finite amount of time, energy and willpower.

So how important is practicality in the real world when it comes to health recommendations? The Journal of the American Medical Association recently published a giant meta-analysis to answer the question “what diet works best?” by comparing the results of 59 individual weight-loss studies. Which diet won? The surprising answer was that there were no major differences in outcomes between diets, and success was completely dependent on what the individual could stick with. In other words, practicality reigned king.

So as summer approaches and everyone begins facing down the reality of the #Quarantine15, one of the more common questions I’m hearing from patients at Ascent Chiropractic is “Where do I start to drop this extra weight?”

35% of Americans have gained unwanted weight over the past year, adding an average of nearly 29 pounds. Via Morning Consult.

A Rundown on Calories

At the most basic level, weight loss and weight gain are dependent on calorie consumption vs. expenditure. We lose weight when we eat less calories than we expend. On the other hand, we gain weight when we consume more calories than we burn. In order to lose one pound of fat, we must create a 3,500 calorie deficit, which can be achieved either through exercise or diet.

Let’s say that a 200 pound man wants to lose one pound in a week. Through exercise alone, he needs to run about 3.5 miles per day (or 24.5 miles total), assuming his diet stays the same. Through dieting alone, he needs to cut back 500 calories/day (the equivalent of a bagel with cream cheese). Theoretically, the two should achieve the same weight loss results.

But in the real world, it’s a whole lot easier to make dietary changes than find the time to exercise to get the same effects.

What Does the Research Say?

A 2010 study published in the International Journal of Obesity shows just how difficult losing weight via exercise can be in the real world. The researchers randomly assigned 320 women to a control group (with no additional exercise) or an exercise group, in which they were instructed to perform 45 minutes worth of moderate-vigorous aerobic exercise, 5 times a week for a year. Both groups were instructed not to change their diets.

A year later, the exercise group had lost an average of 4.4 extra pounds compared to the control group. Sure, dropping 5 pounds is great, but the experiment reveals why exercise-only weight loss plans usually fail.

While the exercise group were instructed to exercise 5 times a week, what they actually did was exercise about three and a half days per week for 45 minutes each. That means they had to exercise approximately 35 hours to lose a pound of weight. Most people would balk at that trade-off.

Now compare that to the nutrition professor who went on a “Twinkie Diet” and subsequently lost 27 pound in 10 weeks, solely through calorie restriction (with no additional exercise).

Why’s It So Difficult To Lose Weight Through Exercise?

There’s a simple explanation for why losing weight really all comes down to your diet: The calories you burn through exercise are relatively insignificant in the grand scheme of things.

We spend most of our calories every day simply staying alive – known as our “resting metabolic rate.” The easiest way to estimate this number is with the Katch-McArdle formula:

Resting Metabolic Rate = (9.81 x lean body mass) + 370 calories per day

For example, if you weigh 150 pounds at 30% body fat, your body burns 1400 calories every day just keeping itself going.

An extra 10% on top of that is what’s known as the Thermic Effect of Food – the energy you spend digesting and processing what you eat.

Another 10-30% on top of that is burned through NEAT (Non-Exercise Adaptive Thermogenesis); that’s any physical activity that’s not exercise. NEAT is one of the biggest variables when it comes to metabolism. It can account for as little as 100 calories to as much as 700 calories a day.

That means that just going about your daily routine is already burning around 2000 calories a day.

Adding exercise into the equation barely makes a dent in your overall caloric expenditure; most of the work is done before you even put on your running shoes. Going to the gym and hitting the elliptical for half an hour is only going to burn in the neighborhood of 250 calories.

To put that in perspective, you can get the same (caloric) effect by simply swapping that 20oz Coke you drink at lunch with water.

There’s also something experts call metabolic compensation that throws a wrench into the weight loss process. A 2015 meta-review of 28 different weight loss studies found that, even with careful monitoring of calorie intake and strict adherence to workout programs, those who utilize only exercise lose 55-64% less weight than expected.

That’s because your body will actually reduce it’s resting (or basal) metabolic rate to try to correct for the mismatch in the number or calories you’re burning. Those on exercise-based weight loss programs will need to burn more calories through exercise than those on diet-based programs will need to cut from their diet to achieve the same amount of weight loss.

This is why people training for a marathon sometimes unexpectedly gain weight. It’s actually an evolutionary mechanism to defend against weight loss (thanks a lot, body).

Now I’m not saying that you shouldn’t exercise. In fact, regular exercise is so inextricably linked to literally every aspect of your health that it’s absurd to think that you can be healthy without it.

But if weight loss is your primary concern, the calories you burn in the gym don’t count for much. The fact is weight loss is 90% diet and 10% exercise.

Next Steps

Where to go from here? If your goal is to drop the extra pounds for summer, here’s where to start.

1. Determine your resting metabolic rate – how many calories you burn every day. You can use OmniCalculator’s tool here.

2. Start tracking your calorie intake – LoseIt! is one of the easiest apps to use.

3. Set your calorie intake goal to 80% of your maintenance calories. Any time you decrease your caloric intake, it’s helpful to simultaneously increase your amount of protein in order to stay satiated. Protein also has the highest Thermic Effect of Food out of any macronutrient, meaning your body needs to expend more energy to digest it in comparison to carbs or fats.

4. If (or when) you get burnt out on counting calories, shift to early time-restricted intermittent fasting. Early time-restricted intermittent fasting is a version of 16:8 plan, which involves 16 hours of fasting and 8 during which you can eat whatever you’d like. Early time-restricted feeding just means you start your 8 hour eating window shortly after rising and begin your fast in the afternoon. Study after study has shown that time-restricted intermittent fasting is far and away the most practical and long-term sustainable approach to losing weight.

You’ll notice that exercise isn’t even mentioned in the recommendations above. But while you shouldn’t be factoring exercise into your caloric expenditure, the benefits are undeniable and you should still be getting it in every day.

Share what you’ve learned!

We want our entire community to be healthier and stronger so they can do more of what they love.

Good nutritional habits, proper exercise and regular chiropractic care to keep your musculoskeletal system working optimally are the best ways to reach that goal. Need a chiropractor in the Brookfield, Waukesha, Wauwatosa, or New Berlin areas? Call us at 262-345-4155 to make an appointment or use our online scheduling app – we’d love to help you get the most out of your body!

About the Author

Dr. Grant Radermacher

Dr. Grant Radermacher is a Brookfield, WI chiropractor providing unmatched results through gentle, evidence-based chiropractic care. Our mission is simple: get you out of pain so you can get back to being you, only better.

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