If you were hoping to read this and find some magic exercise to help you lose a stone then you'll be disappointed. What you will find however is the truth about what exercises are more beneficial.

First of all we need to look at big muscle groups. The biggest muscle groups in our bodies are legs, followed by back and then chest. So with this being said if you have a lot of body fat to lose, would it be beneficial to you to be doing bicep curls (that only target the bicep?).

- 
What we need to look at are what we call "Compound Movements". These are movements that require movement at more than one joint. For example a Leg press. 
Dont spend too much time focusing on the smaller muscle groups, all muscles worked burn calories, however its much more beneficial to target bigger muscle groups, in turn burning more calories throughout your workout.