Myth: If You Exercise, You Don’t Need to Worry About What you eat.


Myth: If You Eat and Exercise Consistently, You Will Never Gain Weight

Man and woman workout with jumping rope
Man and woman jumping rope

If you exercise once a day, every day, the theory that you can eat whatever you want and not gain weight or fat is utter malarkey.  All the indulgent calories that you consume will just be offset by all the exercise, right?  Sadly, this is false.  Although it sounds like an excellent concept, it just doesn’t work this way due to science.  There are very few statements that rank as high on my BS meter.  Sure some people have faster metabolisms and might be able to eat whatever they want and not gain weight, but most of us will gain weight if we fall into the trap.

To avoid weight gain, you still need to be willing to make lifestyle changes, and dietary adjustments as you age or alter your activity level or you will expand your waistline. The fact is, our metabolisms slow as we age.  This slowing happens for several reasons, and these include reduced growth, less activity, and reduced muscle mass.  It is most pronounced at about age 40 and beyond, but don’t look for the nearest high-rise because this is a very slow process. 

Scientifically, it makes sense that you could just burn off the excess calories from a momentary indiscretion.  Say, you eat 750 calories of pizza for lunch.  For discussion’s sake, let’s discuss this in the context of a 1,500 calorie weight loss diet.  Your limit should be 400-500 calories per meal depending on your weight loss goals and lean body mass.  That is an extra 250 calories in your lunchtime meal.  Now, you have to shave off 250 calories from your snacks and dinner or walk at a brisk pace for 1/2 hour.  This plan assumes that you will not have any other dietary splurges for the day.

It is all calorie balance.  If you consume more calories than you need for activity and maintenance of your body, you will gain weight.  Exercise is essential, but it is a poor way to burn calories.  Although I used the term malarkey, there is a speck of truth to the concept that if you exercise consistently, you can avoid weight gain, but the key thing that is missing in the statement is you also will have to watch what you eat.  Over time, you must burn off the excess calories you consume.  If you eat 1,000 excess calories this week, you have to burn an extra 1,000 calories to avoid weight gain.  

Woman Resting Against Tree
Woman Resting Against Tree

The problem is that most of us do not hold ourselves accountable.  We do not keep a diet and exercise journal, so we truly do not balance our calories.  We tend to overestimate the number of calories we burn with exercise and underestimate the number of calories we consume.  These little misestimations usually end up with a 50-150 calorie surplus each day or 1/2 to 1 pound of weight gain per month.  

Don’t justify poor behavior.  The concept of working off excess calories with more exercise is a terrible idea.  Avoiding foods you enjoy will only increase cravings, but you still need to limit the number of portions and portion sizes.  While you shouldn’t allow yourself to eat anything at all times because you work out, there is some truth to the idea that you won’t gain weight if you burn off the excess calories that you ingest. However, to truly burn off your excess calories, you need to take careful note of the number of calories in the foods you eat as well as the number of calories your workout routine likely burns off.  Taking a walk every few days can be good exercise, but it’s not as intense as advanced strength training or running a marathon. Eating an entire cake, then, may not be burned off by your regular walks and you may need to engage in more rigorous workout activity to “justify” the indulgence.

There is a huge difference between occasional indulgence and overeating.  I compare this to a question I ask on alcohol consumption.  At least several times a year, a patient tells me that they drink occasionally.  I always ask “how often does the occasion occur?”.  About 50% of the time, the answer is 2-3 times a week.   The point of this story is it depends on your definition of the word “occasionally.”  To me, it would be 1-2 times a month, and 2-3 times a week is regularly.  No amount of working out will make up for regular indiscretions in your dietary intake.  

Reward yourself but don’t over-reward yourself.  Treating yourself to a weekly treat won’t kill your diet unless you eat the whole bag of treats.  If I follow my diet entirely through the day, I treat myself to 1/4 to 1/2 of a serving of Jelly Belly or M&Ms. Which is 40-80 calories.  I know they add up, but it limits my craving for things that are sweet.  The key is not to binge. 

The bottom line: If you spent 8-10 hours a day in the gym, you might be able to live by the mantra that intake does not matter as long as you exercise every day.  Unfortunately, for the rest of us in the real world, we will have to resort to moderation and control of our food choices with added exercise.

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About the Author

I am a family physician who has served in the US Army. In 2016, I found myself overweight, out of shape, and unhealthy, so I made a change to improve my health. This blog is the chronology of my path to better health and what I have learned along the way.

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