Diet vs. exercise: Which is better for weight loss?

By Allana Kerr, KSL.com Contributor | Posted - Apr. 7, 2016 at 8:32 p.m.

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SALT LAKE CITY — You’ve likely heard the phrase “eat less, move more” to describe a simple approach to weight loss. While simplicity is important, the notion that diet and exercise have an equal effect on weight can be misleading.

Which one really pulls the weight?

Despite what intuition tells us, the role of exercise in weight loss is frequently overemphasized. Truth be told, according to U.S. National Library of Medicine the impact of dietary changes on weight loss is strong, while the impact from exercise is shockingly weak.

Calories in trumps calories out

The obesity epidemic is regularly blamed on the idea that humans have slowed down over time. Simply put, less physical activity should mean fewer calories burned. A study published in the International Journal of Obesity refutes this myth and indicates that energy expenditure hasn’t changed over the past few decades. If people aren’t burning any fewer calories, then why has the rate of obesity doubled since 1980?

According to a 2009 study by the American Society for Nutrition, daily calorie intakes in the early 2000s were 500 calories more than those in the 1970s, and that correlates precisely to the weight gain seen across America over the same time period. These findings suggest that sedentary lifestyles are not driving the obesity epidemic, and people should focus more on calories eaten in an attempt to reverse weight trends.

Using food as reward comes at a cost

After exercising, it’s compulsory to reward the calorie burn with extra calories in. You may load your plate with food more generously after a workout or indulge in dessert “because you exercised”. It’s easy to feel the right to indulge since exercising makes you feel hungrier, paired with the fact that cardio machines conveniently display your calorie expenditure. Unfortunately, these numbers will likely overestimate how many calories you actually burned.

As physicist Alex Hutchinson explains in the book "The Diet Fix," if you burn 88 calories walking a mile on the treadmill, 36 of those calories account for your resting energy expenditure. In other words, you would have burned 36 calories even if you skipped the gym and stayed at home on the couch. Resist the urge to let these reported calories act as a trigger to eat more, which can put you at risk of adding on extra pounds in the long run.

Exercise takes the credit for diet’s work

While some people overindulge due to exercise, others instinctively change their eating habits for the better. If you’ve achieved weight loss with an exercise regime, your success may be related to the coinciding start of a diet regime. Increasing exercise can motivate you to eat healthier, which, in turn, may be facilitating weight loss rather than the increased movement.


What would happen if you started exercising without changing your eating habits? One study published in the Annals of Family Medicine looked at walking programs conducted with no diet changes. For every 10.5 miles walked, participants lost just over one-tenth of a pound. In other words, you need to cover the distance of four marathons to lose just one pound.

Losing one pound solely through exercise sounds strenuous. How much would it take to lose one pound solely through diet? If you cut out 500 calories per day (such as one bagel with cream cheese) then you will lose one pound in just one week, no marathons needed.

Body composition is underrated

The Physical Activity Guidelines for Americans recommend 150 minutes per week of moderate-intensity aerobic activity, such as water aerobics or brisk walking. In a 2014 study published in the British Journal of Sports Medicine on men who exercised beyond the recommended guidelines, their activity level was still not enough to illicit weight loss. In fact, these men gained an average of 12 pounds over 33 years.

Could the lack of weight loss with exercise be due to muscle gain? With a workout regime, you may notice that you look trimmer but the scale hasn’t budged. If you gain one pound of muscle and lose one pound of fat, it’s true that you’ll weigh the same amount.

The difference is that muscle is denser than fat, so it takes up less space on your body, according to Kristen Stewart of everydayhealth.com. Instead of focusing on the scale, focus more on how you feel, how your clothes are fitting, and how your body has changed.

So, should you ditch the exercise? Although it seems exercise does not have an impact on weight loss, it can play an important role in preventing weight gain. Most importantly, exercise is one of the best things you can do for your health irrespective of weight.

According to the Centers for Disease Control and Prevention, physical activity lowers your risk of heart disease, stroke, Type 2 diabetes, depression and some cancers. It also helps to boost energy levels, productivity and memory while relieving stress and anxiety. Ultimately, exercise improves your daily life and helps you to live longer. Who wouldn’t take those odds?

About the Author: Allana Kerr -----------------------------

Allana is a Registered Dietitian who relocated to Utah after working at a remote hospital in Northern Canada. Her nutrition philosophy focuses on individuality and cultivating a positive relationship with food.

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