Kinect Sports

From the main menu select Calorie Challenge and choose Peppy Pizza as your opponent (far right). You need to burn 238 calories in 30 minutes to beat Peppy Pizza. Mini-games will be randomly selected, so if you're trying to do this legitimately you'll need a bit of luck. Now, I say "legitimately" because there is a much easier way to burn calories than actually playing the mini-games properly.

For most of the mini-games, you simply want to swing your arms across your body, as if you're hugging yourself. Give it a try now if you like, you probably deserve a hug. While swinging your arms and hugging yourself, kick with your legs. Your leg movement doesn't need to be excessive, just enough for the game to register that you're moving them. So no River Dancing. Unless the mood strikes you, in which case, go for it.

The games where the above method doesn't work too well are Javelin and Hurdles/Rapid Runner. For Javelin, if you swing your arms too far across your body, you will sometimes grab the javelin. You don't want this, as you will be unable to kick your legs (it will make you run). Instead, swing your arms straight back and forth. Hip thrusting optional.

Hurdles and Rapid Runner are both great mini-games for burning calories. However, they do require a lot of exertion. You can hold a controller and hit the guide button if you become tired. Hit the guide button again when you feel ready. When running, you want to get your knees up as high as possible and swing your arms as if you were marching. If at any stage your self-worth drops due to how silly you look, resume hugging yourself.

Using this guide you should not have any problems burning enough calories to beat Peppy Pizza. The achievement will pop when the timer reaches 30 minutes and you are taken to the results screen, not when you pass 238 calories.

If you are struggling with this achievement don't forget that you can press the guide button to pause the game at any time. And move your arms as much as you can.

Best Solution if you still struggle to make it in time!

I do recommend using a big towel, it is easy that way.
Move sideways and wave the towel. Not really necessary to move sideways so much but I do think it speeds it up a bit. What really speeds it up is if you wave harder with the towel, I mean wafe faster. Make it so it reach the floor and just wave very fast to increase the calories.

When you randomly get the table tennis were you can score points between 1,2,3. Just dont serve and stand still with the towel in your hand. (More safer way is to actually not choose left or right hand as you can make calories run from there. This way you wont accidently serve).

You can reach your target here without ending the game as the timer never starts until you serve but your calories goes up.

I also noticed it should also work with one of the bowling events. (Not the one were they charge at you).

The achievement unlocks when you have done all the 30 minutes so you need to play it out.

IMPORTANT NOTE: If you do this trick, the in game timer will be wrong and you will go overtime and have to play many extra events so you dont really need to get all calories in one go using this trick as you for example would still have to do all that time after. I had to play up to 36 minutes vs the pizza using this trick.