I wouldn't recommend them... I'm no doctor but father said he used to live on them when he worked as a manager. Now he is suffering from severe health issues (heart, diabetes, joints). I don't think any one could say that they're the cause, but I'm sure they didn't help!
You will find a balanced, consistent and thoroughly researched diet will give you all the energy you'll need. Motivation, however, is a mind set. Apparently it takes 21 days to make something a habit, so carry on until it becomes a habit. The day you miss a gym session after those 21 days you'll feel fat and horrible for not going. However, by taking this approach in my mind I have found myself about 2 months down the line to easily fall out of the habit I started with. Push push push!