Fitness Fact: Why Exercise Won’t Help You Lose Weight

I know, I know. You are probably thinking that I made an error typing out the title of this blog post. Nope. Despite the fact that I am a registered dietitian, certified personal trainer, and group exercise instructor in Cambridge, MA I firmly believe that using exercise as a means to lose weight can actually be harmful. Yes, you heard me right. And I wanted to yell Hallelujah when I came across this 
Time article “Why Exercise Won’t Make You Thin.” Please take the time to read it! Then forward it along to all of your family members and friends.

Here are the basic take home points I’d like you to think about:
1. Intense bouts of calorie-burning exercise (think 60 minutes on a piece of cardio equipment or your favorite cycling class) stimulate your appetite. Consequently, most people unknowingly eat more calories than they just burned after intense exercise. If you don’t believe me, check out the research cited in the Times article under the heading “The Compensation Problem.”

I have a saying which goes “You can’t outrun your fork.” And it’s true. We can eat in 10 minutes what would take us 10 hours to burn off. I’m sorry for that- it’s simply the way we humans have evolved.

2. Replacing fat tissue with lean muscle mass does not do much to increase our metabolic rates- no matter how much your personal trainer would like you to believe otherwise. In fact, replacing 10 lbs of fat with 10 lbs of muscle leads to a paltry increase of 40 calories burned. 40 calories? That’s the equivalent of 2 Hershey’s Kisses- just 2!

3.) A butt-blasting, cardio kicking workout often creates the halo effect. How many times have you finished an intense workout, only to indulge afterwards. Hey, you burned a lot of calories after that 60 minute hill climb on the treadmill. Next thing you know, you’ve gone totally overboard at dinner…but with good intentions to “make up for it” tomorrow. It’s an endless and tireless feedback loop.

I have seen this feedback loop in full force in the work I do in eating disorders as well as working with healthy populations. Using exercise to burn calories fuels disordered eating patterns (i.e. a few extra cookies because you’ve been “good.”)

4.) Excessive exercise can lead to overly sore muscles and a feeling of heaviness that can actually lead to more hours of sedentary down time when you aren’t working out.

Please know that I am not suggesting that you stop exercising all together. Exercise provides a host of benefits:
**Enhances heart health and helps to prevent chronic disease
**Improves mental capacity and cognitive ability
**Helps regulate mood by decreasing anxiety and improving feelings of depression
**Enhances stamina
**Supports a healthy immune system
**Helps maintain muscle mass and flexibility, which is crucial for maintaining function as we age
**Improves balance and helps to prevent falls in the elderly

This is not an exhaustive list. Clearly I’m in full support of a healthy exercise program. But the research shows that the benefits of exercise can be obtained at moderate intensities for moderate amounts of time. So now that you don’t have to spend hours burning up calories at your local gym, I wonder how you could use your time more positively. Hmmm, now that’s something to think about.


  1. I love your site and your blog, Marci. Here’s my question: how much is too much exercise? If I find myself eating more than I normally do, I assume that’s a clue. Any more specific guidance for frequency, duration and intensity of exercise that will deliver the benefits without the drawbacks?


  2. Great question Cynthia. And to be honest, I don’t have a clear cut answer for you because it really depends on your goals. We do know that the research shows health benefits of exercise around 30 minutes of moderate exercise per day. So averaging for 3-4 hours per week will you give the health benefits.

    What you may want to consider doing is taking a week to track your current workouts (type, time, intensity) along with your food (including hunger levels). And see what interesting information you discover. Then experiment.

    Taper down the following week and see if you notice any shifts in your body. Since everybody is different, no recommendation works the same across the board. But as you begin to pay close attention to what your body is telling you, you may discover some pretty interesting information. I wouldn’t change too many things too quickly though. That would just skew your results. I’d suggest making one specific change then noting it for a couple of weeks.

    I’d be eager to hear your results in the next month or so.

  3. Loved this post! I’ve heard all this before, but it is really hard to lose the idea that tons of exercise is what will make me “thin,” i swear it’s burned into my brain! Thanks for the post. It’s always great to remind myself that the world will not end if i miss an exercise day.

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