Why Exercise Doesn’t Always Cause Weight Loss

It’s frustrating when you’re working hard at the gym and not shedding body fat, but a study may explain why. In a study published in Medicine and Science in Sports and Exercise, researchers looked at the relationship between exercise and weight loss in a group of 34 overweight and obese women. These previously sedentary women embarked on an 8-week exercise program that included 150 minutes of moderate-intensity aerobic exercise each week. During the times they weren’t actively exercising, they kept records of their physical activity. They also kept a detailed food diary.


At the end of the study, only 11 of the women lost the amount of body fat that would have been predicted by the amount of calories they burned through exercise. The other 23 either didn’t lose body fat or lost less than would be predicted. The reason? After looking at their non-exercise related physical activity, they made an interesting discovery. The women who didn’t lose body fat spent less time moving around when they weren’t working out. There were no differences in the amount of food that each group ate, although some studies show that people eat more when they exercise regularly.


In other words, the women that didn’t lose weight on the exercise program were more likely to head home after their workout and take it easy rather than staying active. Even though they burned off calories through formal exercise, they reduced the amount of activity they did later on when they weren’t working out. This may be one explanation for why some people exercise and don’t get the amount of weight loss they expected.


What Does This Mean?

A workout at the gym won’t have as much impact if you spend the rest of the time lounging in an easy chair. There’s the concept of NEAT or non-exercise activity thermogenesis. It refers to the calories you burn when you’re not working out, sleeping or eating a meal. It includes activities like walking around, cleaning house and fidgeting. Research shows that this type of activity plays an important role in weight control. Furthermore, your body may compensate for a hard workout by trying to conserve energy. That’s why you have to override those signals and keep moving. High-intensity exercise also has some advantages over moderate-intensity workouts since there’s more of an afterburn, which increases the number of calories burned even after a workout is over.


Exercise and Weight Loss: The Bottom Line?

If you’re trying to shed body fat, don’t assume you can be inactive for the rest of the day just because you exercised. Make a conscious effort to keep moving as much as possible throughout the day, taking breaks to walk around frequently if you work at a desk. There are other advantages to prolonged sitting. It increases your risk of mortality. Keep moving even after you get home from the gym.



Medicine and Science in Sports and Exercise. 2010: 42(6): 1121-1128.
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Am J Epidemiol. 2010 Aug 15;172(4):419-29. Epub 2010 Jul 22.