Which Impacts Your Weight More: Exercise or Diet?

which is more importantby Melissa Diane Smith

Knowing the right answer to that question can make a difference in whether you drop excess pounds or not.

Q: I want to lose weight in the new year. I am thinking of joining a gym and starting a regular exercise program to drop the extra pounds. Is exercise really more important for losing weight than what I eat?

A:  No, it’s not. Scientific evidence supports that changing your diet is the most important factor – and much more important than physical activity – in whether you lose unwanted weight. Furthermore, whether you believe that or not appears to have a big bearing on controlling your weight.

Virtually all of us have heard that we can eat anything we want “in moderation” and burn off the extra calories through exercise to lose or maintain our weight. But the 2014 documentary Fed Up says: “Everything we’ve been told about food and exercise for the past 30 years is dead wrong.” The idea that we can exercise away excess weight is a message food manufacturers have pushed on all of us; health professionals, the media, and television shows have picked up on it; and we now accept it as fact. But following that strategy isn’t working for people who need to lose weight, and that’s why the United States and other countries are not winning the battle of the bulge.

Fed Up explains that the food industry adds high-calorie, high-carbohydrate, nutrient-void sugar to 80 percent of the foods offered in a typical supermarket and wants us to believe that we can eat and drink any sugar-rich foods and beverages it creates without gaining weight or developing any health problems from doing that. Consequently, countless people start each new year off ignoring the importance of the type and quality of the food and drinks they consume and vowing to hit the gym hard. They keep trying to exercise more and usually fail and give up on losing weight within the first month of trying.

The Scoop on Exercise

Exercise offers numerous benefits, such as keeping certain diseases like heart disease at bay, boosting your mood, and improving sleep. But repeated studies have shown that many people who begin an exercise program lose little or no weight. Some, especially those who do fiery spurts of vigorous exercise, gain weight. Sure, exercise burns calories, but it also can stimulate hunger and cause us to eat more calories – in effect, canceling any weight-loss benefits we thought we might receive.

Research indicates that people who exercise strenuously eat more calories throughout the day than those who don’t. Whether that’s because exercise makes people more hungry or because people are more tired, have less self-control, or want to reward themselves after pushing themselves to work out, it’s common for people to both eat more foods and eat junkier foods after going to the gym. This phenomenon is so common, it’s something TIME magazine wrote about in a 2009 article entitled “Why Exercise Won’t Make You Thin.”

What You Believe is Important

Your everyday beliefs about whether you believe exercise or diet is the key to weight loss guide your actions and the actual likelihood of being overweight, according to six studies published in 2013 in the journal Psychological Science. In the studies, researchers asked a total of more than 1,200 people in the U.S. and four other countries about the main factor that makes people overweight. They found that those who said it’s most important to exercise to prevent obesity had a higher body mass index (BMI) – in other words, were more likely to be overweight – than the people who said eating right was the key. In two of the studies, when researchers offered participants unlimited chocolate, those who said they think staying active is the key to maintaining a healthy weight, ate more.

So, if you are serious about wanting to lose weight effectively this year, restructure your beliefs. Buck the frenetic exercise trend and focus on what you eat. That’s the part of the obesity and overweight problem nearly everyone has missed.

Copyright 2015 Melissa Diane Smith


Want more in-depth help on how to lose weight from me? Learn about my 2015 New Year’s special on nutrition counseling or coaching here or see my Nutrition Consultations and Coaching page here.


I am the Ask the Nutritionist columnist in 2015 for Better Nutrition magazine, and the answer above is my first column for the new year. Feel free to send a question you would like answered in the column to email hidden; JavaScript is required.


Selected References:

Fed Up [documentary]. Directed by Stephanie Soechtig. Atlas Films, 2014.

Cloud, John. The Myth About Exercise: Why Exercise Won’t Make You Thin. TIME, August 17, 2009, pgs. 42-47.

Beliefs about Causes of Obesity May Impact Weight, Eating Behavior. Association for Psychological Science, June 18. 2013. http://www.psychologicalscience.org/index.php/news/releases/beliefs-about-causes-of-obesity-may-impact-weight-eating-behavior.html.

McFerran, Brent, Mukhopadhyay, Anirban. Lay Theories of Obesity Predict Actual Body Mass. Psychological Science, June 10, 2013. DOI: 10.1177/o956797612473121.

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