Everywhere I turn, some variation on this graphic is being posted by fitness blogs. This isn’t even remotely true. People really need to stop spreading this (misspelled) meme around.
First of all, doing a specific number of jumping jacks will not burn the same number of calories for every individual. It isn’t solely the the rep count the defines how much energy you use: Your age, gender, weight, muscle mass, your heart rate, the exercise’s duration, the exercise’s intensity, how your metabolism works, how hot or cold you are, the amount of stress you’re under, how much adrenaline is going through your body - There are so many factors here. You could do the same number of jumping jacks every day and burn a different amount each time.
Second, the math here is ridiculously off. The average person does not burn .5 calories per jumping jack. Two little jumps do not take that much energy.
According to LiveStrong:
[A] person who weighs 150 pounds will burn about 153 calories during a 30-minute moderate-intensity bout of jumping jacks. A person who weighs 200-pounds will burn approximately 204 calories during a 30-minute moderate-intensity jumping jacks workout. While you’re likely unable to perform jumping jacks for 30-minutes straight, this means a 150-pound person will burn about 5.1 calories per minute and a 200-pound person will burn about 6.8 calories per minute.
So if the average 150 pound person can do about 75 jumping jacks per minute, and you burn 153 calories within 30 minutes, you’re burning about .068 calories per jumping jack. That means it would take over 11 hours for you to (potentially) burn one pound, after doing a total of about 49,500 jumping jacks.
And third: Calories, weight loss and energy consumption do not work this way. Our bodies are complicated entities and are subject to an incredible amount of nuance. Just like how your metabolism is subjected to all the factors I listed above, so is your weight loss. Doing a certain amount of exercise will not guarantee that you lose a certain amount of weight. You need to take into account your diet, lifestyle, environment, body content, fitness routine, water retention, etc.
There is no straightforward answer when it comes to predicting the future. No one knows for sure whether you’ll lose one pound from this routine. Maybe you will. Maybe you’ll lose more. Or maybe you won’t. Maybe you’ll gain weight. What’s actually important is whether or not you enjoy your lifestyle and are feeling fulfilled, happy and confident. Don’t get caught up in this numbers game.